Publications of the University of Eastern Finland
Dissertations in Forestry and Natural Sciences
isbn: 978-952-61-1560-3 (printed)
issnl: 1798-5668
issn: 1798-5668
isbn 978-952-61-1561-0 (pdf)
issnl: 1798-5668
issn: 1798-5676
dissertations | 154 | Sanna Leppänen | Effect of host-plant use on speciation and parasitoid community structure in internal-feeding sawflies
Sanna Leppänen
Effect of host-plant use on
speciation and parasitoid
community structure in
internal-feeding sawflies
Sanna Leppänen
Effect of host-plant use on
speciation and parasitoid
community structure in
internal-feeding sawflies
Publications of the University of Eastern Finland
Dissertations in Forestry and Natural Sciences
SANNA LEPPÄNEN
Effect of host-plant use on
speciation and parasitoid
community structure in
internal-feeding sawflies
Publications of the University of Eastern Finland
Dissertations in Forestry and Natural Sciences
154
Academic Dissertation
To be presented by permission of the Faculty of Science and Forestry for public
examination in the Auditorium N100 in Natura Building at the University of Eastern
Finland, Joensuu, on September, 19, 2014, at 12 o’clock.
Department of Biology
Grano
Joensuu, 2014
Editors: Prof. Pertti Pasanen,
Prof. Pekka Kilpeläinen, Prof. Kai Peiponen, Prof. Matti Vornanen
Distribution:
Eastern Finland University Library / Sales of publications
P.O.Box 107, FI-80101 Joensuu, Finland
tel. +358-50-3058396
http://www.uef.fi/kirjasto
ISBN: 978-952-61-1560-3 (printed)
ISSNL: 1798-5668
ISSN: 1798-5668
ISBN 978-952-61-1561-0 (PDF)
ISSNL: 1798-5668
ISSN: 1798-5676
Author’s address:
University of Eastern Finland
Department of Biology
P.O.Box 111
80101 JOENSUU
FINLAND
email: [email protected]
Supervisors:
Associate professor Tommi Nyman, Ph.D.
University of Eastern Finland
Department of Biology
P.O.Box 111
80101 JOENSUU
FINLAND
email: [email protected]
Professor Heikki Roininen, Ph.D.
University of Eastern Finland
Department of Biology
P.O.Box 111
80101 JOENSUU
FINLAND
email: [email protected]
Reviewers:
Docent Niklas Janz, Ph.D
Stockholm University
Department of Zoology
106 91 STOCKHOLM
SWEDEN
email: [email protected]
Research scientist Carlos Lopez-Vaamonde, Ph.D
Institut National de la Recherche Aqronomique (INRA)
Zoologie Forestière
45075 ORLÉANS
FRANCE
email: [email protected]
Opponent:
Professor Niklas Wahlberg, Ph.D
University of Turku
Department of Biology
20014 TURKU
FINLAND
email: [email protected]
ABSTRACT
Plants, herbivorous insects, and parasitoids form a major part of
all described species. Still, the evolutionary processes that have
led to the formation of these diverse food webs with extremely
complex multitrophic interactions are not fully understood.
Insect–plant interactions are taxonomically conserved in the
sense that herbivores tend to use closely related host plants, but
host–plant shifts are common in most insect taxa. There is
evidence that shifts among host plants can influence insect
speciation, but the effects of niche shifts on higher trophic levels
remain a mystery. In addition, the third trophic level (especially
parasitoids) could be the driving force behind insect
diversification by causing insects to shift host plants. Using
molecular-genetic methods, this thesis tries to answer how host
plants influence speciation in leaf-mining and gall-inducing
sawflies and in their associated parasitoids. My main purpose
was to investigate the determinants of tritrophic associations,
and the role of parasitoids in herbivore speciation.
A molecular-phylogenetic analysis of leaf-mining sawflies in
the subfamily Heterarthrinae indicates that the subfamily
originated c. 100 million years ago, which means that the
leafminers are younger than their main host taxa.
Reconstructions of larval feeding modes show that transitions
from external to internal feeding have occurred multiple times
within the superfamily Tenthredinoidea, but also that leafmining has arisen only twice. On long time scales, host–plant
use is taxonomically unstable, and multiple convergent host
shifts have happened during the evolutionary history of
Heterarthrinae.
Host-plant shifts also seem to promote genetic differentiation
and speciation in gall-inducing sawflies belonging to the genera
Pontania and Euura, as clear host-based clustering of individuals
is observable in phylogenetic trees. Indeed, hierarchical
AMOVAs indicated that most of the genetic variation in both
galler genera is explained by willow host species rather than by
geographic location. The results show that host-associated
differentiation has a huge impact on galler speciation, but also
that host-associated differentiation is not completely repeatable:
the two galler genera have similar host plant repertoires, but ΦST
estimates among population samples collected from specific
willow species differ markedly.
Parasitoids of both leafminers and gallers represent three
hymenopteran families that are phylogenetically distant from
each other. In the case of miner parasitoids, closely related
parasitoids tend to use the same miner species. However,
phylogeny-based analyses show that the host-plant phylogeny
is a more important factor structuring parasitoid–miner
associations than is the miner phylogeny. The diet breadth of
individual parasitoid species varies, and both niche- and
species-specialist enemies can be found. In combination, the
tritrophic patterns suggest that both bottom–up and top–down
forces have influenced diversification in the plant–leafminer–
parasitoid system.
DNA barcoding proved to be a suitable tool for studying the
structure of leaf-galler parasitoid communities. In galler
parasitoids, habitat (boreal–subarctic vs. arctic–alpine) had the
strongest effect on parasitoid community structure. This
indicates that, in addition to host shifts, colonization of novel
habitats may provide shelter from enemies and accelerate
herbivore speciation. Furthermore, at least two parasitoid
species apparently originated by tracking galler hosts that had
shifted to using dwarf willows that grow in treeless arctic–
alpine habitats.
In combination, the results of the leafminer and galler studies
support the view that parasitoids could be a major driving force
in herbivore speciation, but also that diversification can cascade
up in the food web, when parasitoids form host races attacking
herbivores on novel plant species and niches.
Universal Decimal Classification: 575.858, 575.86, 591.522, 591.531.1,
591.557.8, 595.793
CAB Thesaurus: speciation; coevolution; host plants; herbivores; insects;
Hymenoptera; leaf miners; Pontania; Euura; Pseudodineura; differentiation;
parasitoids; food webs; tritrophic levels; diversification; habitats; phylogeny;
genetic variation; community ecology; DNA; nucleotide sequences; molecular
genetics techniques
Yleinen
suomalainen
isäntäkasvit;
asiasanasto:
kasvinsyöjät;
lajiutuminen;
hyönteiset;
evoluutioekologia;
sahapistiäiset;
parasitoidit;
erilaistuminen; ravintoverkot; habitaatti; fylogenia; geneettinen muuntelu;
DNA-anlyysi; molekyyligenetiikka
Preface
Firstly, the deepest imaginable gratitude goes to my main
supervisor Tommi Nyman for guiding me on every step and
showing me how marvelous creatures sawflies and their
parasitoids are. I also thank professor Heikki Roininen for
encouraging me to begin this project, and all of my coauthors
for their patience and the help they provided. I am very grateful
for my support-group members Tomas Roslin and Marko
Mutanen for their comments and help. I also want to show
gratitude for all the sample collectors: without you my work
would not have been possible.
To our small research group: Mia, you always seemed to
have an answer to all of my problems, and Tobias, you helped
me in the lab and with analysis whenever I needed. I wish to
thank Inna for all coffee breaks we had. Big thanks also belong
to the staff and faculty of the Department of Biology for their
help and for providing resources for my research. I wish to
thank the institutions funding this research project: Academy of
Finland (Project No. 124695 and 14868), the Finnish Cultural
Foundation North Karelia Regional Fund, and the Department
of Biology.
Warmest thanks to all my friends outside the university life,
especially the climbing community in Joensuu, without you I
would not have survived this project. You offered me a break
from the academic world, and for once I had to focus on just one
thing. Finally, I would like to thank my family: mom, dad, and
my sister for their support and having faith in me. Last but not
least, to the love of my life Eero and my son, thanks for bringing
meaning to my life. There are not enough words to say how
grateful I am. You have always stood by me, supported and
pushed me on when I wanted to quit.
Joensuu, August 2014
Sanna Leppänen
LIST OF ABBREVIATIONS
HAD
MP
ML
NJ
AMOVA
COI
Cytb
EF-1α
NAK
Host-associated differentiation
Maximum parsimony
Maximum likelihood
Neighbor-joining
Analysis of molecular variance
Cytochrome oxidase I
Cytochrome b
Elongation factor-1α
Sodium-potassium adenosine triphosphatase
LIST OF ORIGINAL PUBLICATIONS
This thesis is based on data presented in the following articles,
referred to by the Roman numerals I-IV.
I
Leppänen S A, Altenhofer E, Liston A D, and Nyman T.
Phylogenetics and evolution of host-plant use in leaf-mining
sawflies (Hymenoptera: Tenthredinidae: Heterarthrinae).
Molecular Phylogenetics and Evolution 64: 331–341, 2012.
II
Leppänen S A, Malm T, Värri K, and Nyman T. A
comparative analysis of genetic differentiation across six
shared willow host species in leaf- and bud-galling sawflies.
Submitted.
III
IV
Leppänen S A, Altenhofer E, Liston A D, and Nyman T.
Ecological versus phylogenetic determinants of trophic
associations in a plant–leafminer–parasitoid food web.
Evolution 67:1493–1502, 2013.
Nyman T, Leppänen S A, Várkonyi G, Shaw M R, Koivisto R,
Vikberg V, and Roininen H. Determinants of parasitoid
communities of willow-galling sawflies: habitat overrides
phylogeny, host plant, and space. Manuscript.
Some unpublished results are also presented.
Publications are reprinted with the kind permission of John
wiley and sons and Elsevier.
AUTHOR’S CONTRIBUTION
The present author together with her supervisor T. Nyman
planned all the studies. The present author was responsible for
most of the laboratory work and data analyses, and was the
main writer in articles I, II and III. The present author collected
the data and participated in data analysis and writing of article
IV.
Contents
1 Introduction ...................................................................................13 1.1 Plant–insect interactions ............................................................14 1.2 Insect–parasitoid interactions....................................................16
1.3 Aims of this study .......................................................................18 2 Study system ..................................................................................19 2.1 Sawflies .........................................................................................19 2.1.1 Leafminers...................................................................................19 2.1.2 Gall-inducers ..............................................................................21
2.2 Parasitoids ....................................................................................22 3 Materials and Methods ................................................................25 3.1 Material sampling .......................................................................25
3.2 Genetic material...........................................................................26
3.3 Phylogeny reconstruction ..........................................................27
3.4 Insect–plant analyses ..................................................................29
3.5 Analyses of tritrophic interactions ...........................................31 4 Results and Discussion ................................................................33 4.1 Role of plants in insect speciation.............................................33 4.1.1 Leaf-mining sawflies ...................................................................33
4.2.1 Gall-inducing sawflies ................................................................35
4.2 Tritrophic interactions ................................................................37 4.2.2 The parasitoid community of leaf-mining sawflies.....................37
4.2.2 The parasitoid community of gall-inducing sawflies..................39
5 Conclusions ....................................................................................43 6 References.......................................................................................45 1 Introduction
Insects comprise over half of the described species on earth, and
estimates of the number of existing arthropod species range
from 5 to 10 million (Strong et al., 1984; Ødegaard et al., 2005).
The diversity of insects has puzzled researchers for decades
(Ehrlich & Raven, 1964; Strong et al., 1984; Farrell, 1998;
Novotny et al., 2006; Mayhew, 2007). Various factors may have
played role in the insects’ success in colonizing the earth, e.g.,
small size, ability to fly, phytophagy, and old age (McPeek &
Brown, 2007; Mayhew, 2007). A large proportion of insects feed
on plants, and these herbivorous lineages have managed to
spread across the entire angiosperm phylogeny, and have
developed several distinct feeding modes at the same time (Janz,
2011). Mitter et al. (1988) showed that phytophagous insect
groups are on average more diverse than their non-herbivorous
sister taxa.
Like phytophagous insects, parasitoids form a diverse and
species-rich group. Parasitoids have a close connection with
their hosts, so they are usually highly specialized, and cryptic
species are often found (Smith et al., 2006; 2007; Kaartinen et al.,
2010; Gebiola et al., 2012). However, because the degree of
specialization varies at all three trophic levels, plants,
herbivores, and parasitoids normally form very complex
tritrophic interaction networks (Morris et al., 2004; Kitching,
2006; Nyman et al., 2007).
Interactions with other insects or organisms like plants may
enhance “eat or be eaten” situations (coevolution), which may
speed up diversification in one or both of the interacting
lineages (Ehrlich & Raven, 1964; Mitter et al., 1988; Farrell, 1998).
Traditionally, plant-feeding insects have been thought to
coevolve with their host plants (Ehrlich & Raven, 1964; Farrell et
al., 1991). In this coevolutionary model, plants develop new
defensive chemicals allowing them to multiply and diversify,
but later herbivores invade these new plant species, which could
13
lead to adaptive radiation in the herbivores (Ehrlich & Raven,
1964; Farrell, 1998). Cospeciation, where two species speciate in
parallel, can be the result of coevolution, but it is not essential
(Agosta, 2006; Janz, 2011; Althoff et al. 2014). However,
cospeciation is rarely seen between herbivore insects and plants
(Roderick, 1997), and of the few examples that have been found,
maybe the best known is the cophylogeny between figs and fig
wasps (Jackson, 2004). Generally, insects and plants form loose
phylogenetic associations, so that closely related insects are
associated with closely related plants, but with little evidence
for strict, long-term cospeciation (e.g. Janz & Nylin, 1998;
Nyman, 2010; Janz, 2011; Althoff et al. 2014). A similar situation
can be found in the third trophic level, as host phylogeny has
little influence on host–parasitoid associations (LopezVaamonde et al., 2005; Ives & Godfray, 2006; III; IV).
1.1 PLANT–INSECT INTERACTIONS
In general, plant–insect associations are taxonomically
conservative, so that phylogenetically related insects feed on
phylogenetically related plants (Ehrlich & Raven, 1964; Janz &
Nylin, 1998; Farrell, 2001; Novotny et al., 2002; Kergoat et al.,
2007; Winkler & Mitter, 2008). Thus, one would think that host
or niche shifts are rare. “Host shift” refers to a situation where a
population of herbivores has started to use a novel host plant
(Agosta, 2006). Every host shift begins with colonization, so
initially the herbivore retains a capacity to use both plant
species. Later, some herbivores may differentiate to use only the
ancestral or novel host plant, and the populations therefore form
reproductively partially isolated host races, which may
eventually evolve into new, reproductively isolated species
associated with different host plants (Drès & Mallet, 2002;
Berlocher & Feder, 2002; Stireman et al., 2005; Peccoud et al.,
2009). This is possible if there are differences among plant taxa
in chemical, ecological, morphological, and/or phenological
14
traits, so that the plants can act as a source of divergent natural
selection (Funk et al., 2002; Nyman, 2010).
Host shifts are found in a wide variety of insect taxa, but the
role of host shifts in insect speciation is still unclear (LopezVaamonde et al., 2003; Percy et al., 2004; Agosta, 2006; Nyman et
al., 2006a; Winkler & Mitter, 2008). However, host shifts are
thought to be an important driver of herbivore diversification
(Winkler & Mitter, 2008). Ecological shifts do not occur only
between plant species, because evolutionary changes can
involve also, for example, shifts from external to internal feeding
(Nyman et al., 2006a). Recent studies have shown that
diversification of herbivorous insects generally has occurred
later than in their host plants, meaning that present host-use
patterns in insects mainly result from shifting among preexisting plant lineages (Gómez-Zurita et al., 2007; Hunt et al.,
2007; McKenna et al., 2009; Ohshima et al., 2010; Stireman et al.,
2010). Generalism increases the likelihood of host shifts not only
to closely related plant species, but also to novel, distantly
related plants (Agosta et al., 2010; Janz, 2011).
Host-associated differentiation (HAD) occurs when hostplant species has a stronger effect on differentiation in insect
populations than does geographic isolation, so that the insects
form genetically distinct host-associated populations on
alternative hosts (Berlocher & Feder, 2002; Drès & Mallet, 2002;
Stireman et al., 2005; Scheffer & Hawthorne, 2007; Dickey &
Medina, 2012). If HAD is a common process, ecological and
evolutionary divergence according to host plants would be
found in most insects (Stireman et al., 2005). Indeed, existence of
HAD has been demonstrated in numerous insect taxa (Via et al.,
2000; Stireman et al., 2005; Dorchin et al., 2009; Hernández-Vera
et al., 2010; Dickey & Medina, 2010), but few studies have tested
HAD in more than one herbivore–host plant pair (Stireman et
al., 2005; Dickey & Medina, 2010; Dickey & Medina, 2012; Egan
et al. 2013) (II). HAD and resultant ecological speciation
(Schluter, 2001; Rundle & Nosil, 2005) has been used to explain
the extraordinary diversity of phytophagous insects. Ecological
speciation results from divergent selection on traits in different
15
ecological environments, which leads to reproductive isolation
between populations either directly or indirectly (Schluter &
Conte, 2009). In addition to phytophagous insects, ecological
speciation has been studied in a wide variety of groups,
including parasitoids (Stireman et al., 2006), fishes (Schluter &
Conte, 2009), seed-eating birds (Hendry et al., 2009), and lizards
(Rosenblum & Harmon, 2011). However, it still remains
unknown how important HAD really is for insect
diversification, so comparative studies focusing on several
insects that use the same hosts (Stireman et al., 2005; II) provide
good evidence on the commonness and repeatability of the
process.
1.2 INSECT–PARASITOID INTERACTIONS
Many factors can influence how enemies find the host species
that they attack. Plants and herbivores vary in their occurrence
in time and space and, thus, only some of the potential hosts of a
particular parasitoid species may be available at a given time.
Host phylogeny (Desneux et al., 2012) as well as host niche
(Hawkins, 1994) can also influence host acceptance and
suitability. At least some parasitoids use host plants as cues
when searching for their hosts (McCall et al., 1993; De Moraes et
al., 1998; Powell et al., 1998; De Moraes & Mescher, 2004) and, in
gall-inducing insects gall morphology has been shown to affect
parasitism (Price & Clancy 1986; Price et al., 1987; Kopelke, 1999;
Craig et al., 2007; Nyman et al., 2007)
In tritrophic interaction networks, the level of specialization
typically varies at all levels, because diet breadth in both
herbivores and parasitoids ranges from extreme specialization
to broad generalism (Godfray, 1994; Nosil & Mooers, 2005;
Stireman, 2005). Nevertheless, most herbivores use only a small
proportion of the available plant species (Novotny et al., 2010),
and the situation is similar in parasitoids, which mostly attack
only some of the available herbivores (Hawkins, 1994; Cagnolo
et al., 2011). Over longer time scales, such variation in
16
specialization provides the raw material for evolutionary shifts
in associations (Janz, 2011), and many studies have indicated
that niche shifts are an important driving force in the
diversification of plant-feeding insects as well as of their
enemies (Nyman et al., 2007; Fordyce, 2010; Segar et al., 2012). It
has also been suggested that parasitoid pressure could cause
adaptive shifts along other niche dimensions and thereby, for
example, lead to the evolution of gall induction or other internal
feeding habits (Price & Clancy, 1986; Connor & Taverner, 1997).
Diversifying effects can theoretically operate in both “top–
down” and “bottom–up” directions. In the plant-driven
“bottom–up” model, diversification of plants leads to
diversification of herbivores, which, in turn, leads to increased
diversity in parasitoid species (Abrahamson et al., 2003;
Stireman et al., 2006; Forbes et al., 2009). More research has
focused on parasitoid -driven “top–down” diversification, as it
has become evident that natural enemies can influence host–
plant use of herbivores (Bernays & Graham, 1988; Nosil &
Crespi, 2006). This happens if parasitoids preferentially attack
herbivores on specific plant species (Rott & Godfray, 2000;
Murphy, 2004), in which case switches to novel plant species
could provide the herbivores with “enemy-free space,” and
thereby facilitate speciation by niche shifts (Lill et al., 2002;
Singer & Stireman, 2005).
While an extensive literature on the phylogenetic history of
insect–plant interactions exists, only few studies involve a
tritrophic phylogenetic comparison of plants, herbivores, and
parasitoids (Lopez-Vaamonde et al., 2005; Ives & Godfray, 2006;
Nyman et al., 2007; III; IV). Molecular-phylogenetic methods
and DNA barcoding have become important tools for resolving
the history and composition of parasitoid complexes (Smith et
al., 2006; 2007; 2008; 2011; Kaartinen et al., 2010; Hrcek et al.,
2011). Identification of parasitoids based on morphology alone
can be difficult and time-consuming, and rearing can also be
unreliable if parasitoid species differ in rearing success.
Therefore, the use of molecular methods can lead to more
17
accurate estimates of interaction strengths (Kaartinen et al.,
2010; Smith et al., 2011; Wirta et al., 2014).
1.3 AIMS OF THIS STUDY
The aims of this thesis were to explore insect speciation using
leaf-mining and gall-inducing sawflies and their parasitoids as
model systems. In particular, I wanted to resolve the role of host
plants and parasitoids in herbivore speciation, and to explore
speciation in parasitoids. Very few studies have compared more
than one insect–plant pair, meaning that little is known about
the repeatability of HAD. The extreme complexity of tritrophic
interactions between plants, herbivores, and parasitoids make
them demanding to study, so little is known about how
tritrophic interactions are assembled and maintained. Even less
is known about how herbivore host-plant shifts influence
parasitoid speciation, and whether enemy communities of
phytophagous insects are determined mainly by the phylogeny
of the herbivores, by geographic region, or by ecological factors
such as host-plant use or preferred habitat.
The specific aims of this study were:
1. To study the role of host-plant shifts in insect speciation.
(I & II)
2. To investigate repeatability of host-associated genetic
differentiation. (II)
3. To investigate the evolutionary assembly of complex
tritrophic food webs. (III & IV)
4. To explore how parasitoids influence herbivore
speciation, and to study the role of niche and habitat
shifts in parasitoid speciation. (III & IV)
18
2 Study System
2.1 SAWFLIES
2.1.1 Leafminers
Leafminer larvae live between the upper and lower epidermal
layers of leaves (Connor & Taverner, 1997; Sinclair & Hughes,
2010). The habit of leaf mining has evolved independently
multiple times in four insect orders: the Diptera, Lepidoptera,
Coleoptera and Hymenoptera (Hespenheide, 1991; Connor &
Taverner, 1997; Sinclair & Hughes, 2010). The adaptive
significance of leaf-mining may be that the mine shelters the
insect larvae from environmental stress and natural enemies,
and/or helps in avoiding plant defenses (Connor & Taverner,
1997). Leaf-mining lineages are often less species rich than their
external-feeding sister taxa, and miners also tend to specialize
on single plant species or on a few closely related plants (Smith,
1979; Hespenheide, 1991; Connor & Taverner, 1997).
Most hymenopteran leafminers belong to the Tenthredinidae,
which is the largest family of herbivorous symphytans
(Viitasaari, 2002; Davis et al., 2010) (Fig. 1A,B). Within
Tenthredinidae, the leaf-mining habit has evolved twice, in the
subfamily Heterarthrinae and in the nematine tribe
Pseudodineurini (Pschorn-Walcher & Altenhofer, 1989) (I).
Heterarthrinae includes 29 genera and over 150 species, and
heterarthrines are found all over the world except for Africa,
Australia, and Antarctica (Goulet, 1992; Taeger et al., 2010).
Most heterarthrines are quite specialized, using one or a few (in
most cases, woody) plant species as hosts (Smith, 1979; PschornWalcher & Altenhofer, 1989; Taeger & Altenhofer, 1998), but
their collective host range includes over 20 plant genera in ten
families (Smith, 1971; Altenhofer, 2003). The tribe
Pseudodineurini belongs to the subfamily Nematinae and
includes only 12 known species (Taeger et al., 2010).
Pseudodineurini miners are almost exclusively specialized on
19
Figure 1. Examples of sawflies studied in this thesis. Leafminers: A) Scolioneura
betuleti on Betula pubescens ssp. czerepanovii, B) Fenusa ulmi on Ulmus sp. Leaf
gallers: C) Pontania aquilonis on Salix herbacea, D) Pontania nivalis on Salix glauca.
Bud gallers: E) Euura mucronata on Salix glauca, F) Euura lanatae on Salix lanata.
Photos A, B, D and F by T. Nyman, and C and E by S. Leppänen.
20
the plant family Ranunculaceae (Altenhofer, 2003). Larvae of
this tribe emit a typical odor of citral, which is lacking in
Heterarthrinae leafminers (Boevé et al., 2009).
2.1.2 Gallers
Gallers represent a special case of insect–plant interactions, as
the insects have to alter plant morphology to produce a gall in
which their larvae live. Plant galls are generally defined as
pathologically developed cells, tissues, or organs that are
formed by either increasing cell number or size (Meyer, 1987).
The habit of galling has evolved several times in many different
insect orders (Meyer, 1987; Crespi et al., 1997; Nyman et al.,
2000; Cook & Gullan, 2004), producing species-rich groups with
a long history, as the first galls were present already 300 million
years ago (Labandeira & Phillips, 1996). Galls are believed to
provide the gall-inducers with better nutrition, shelter from the
environment, and protection from natural enemies (Price et al.,
1987; Stone & Schönrogge, 2003). Most gallers are very host and
tissue specific (Roininen et al., 2005; Hardy & Cook, 2010). Thus,
in many galler genera, species attack different plants and plant
parts, indicating that there have been shifts and adaptive
radiations into novel ecological niches (Price, 2005).
Most hymenopteran gallers belong to the tenthredinid
subfamily Nematinae (Goulet, 1992; Viitasaari, 2002). The most
species-rich group of nematine gallers is the subtribe Euurina,
which includes c. 400 species that induce leaf folds or rolls, or
various types of closed galls on Salix (a few North American
leaf-folding and -rolling species live on Populus) (Kopelke, 1999;
Roininen et al., 2005). Euurina gallers can be classified by their
gall morphology into three genera: Phyllocolpa species induce
open leaf folds or rolls, Pontania species induce closed leaf galls
(Fig. 1C,D), and Euura species induce bud (Fig. 1E,F), petiole,
shoot, or midrib galls (Smith, 1970; Price & Roininen, 1993;
Kopelke, 1999; Kopelke, 2003). The genus Pontania is divided
into six species groups (dolichura-, herbaceae-, polaris-, vesicator-,
proxima-, and viminalis-group), and Euura is divided into the
21
mucronata-, laeta-, testaceipes-, venusta-, atra-, and amerinae-groups
(Kopelke, 1999; 2003). Euurina gallers live in the Holarctic
region (Smith, 1979; Price & Roininen, 1993; Roininen et al.,
2005), as do their species-rich host group Salix (c. 300–500
species) (Argus, 1997; Skvortsov, 1999).
Phylogenetic studies on Euurina have revealed that gall-type
shifts have been less frequent than host-plant shifts during the
evolutionary history of the group (Nyman et al., 2000; Nyman et
al., 2007). The Euurina gallers’ pronounced host specificity and
close connection with their host plants makes the group an
excellent subject for investigations on ecological speciation and
diversification.
2.2 PARASITOIDS
Parasitoids are arthropods that live in or on another arthropod
species, eventually killing the host individual (Godfray, 1994).
Parasitoids differ from predators in that they use only one
individual as a host. Several different insect orders contain
parasitoid lineages, but most parasitoids belong to either
Hymenoptera or Diptera (Godfray, 1994; Hawkins, 1994). Most
hymenopteran parasitoids belong to the paraphyletic group
“Parasitica” in the suborder Apocrita (Goulet and Huber, 1993).
Hymenopteran parasitoids have specialized ovipositors that are
used for depositing eggs. The parasitoid sting causes paralysis
in a host, which may be permanent, or the host may continue
living (Godfray, 1994). Dipteran parasitoids do not have
ovipositors capable of penetrating plant tissues, so leafminers
and gallers usually lack these parasitoids (Hawkins, 1994).
Parasitoids are usually highly specialized because of their
close connection with their hosts. Parasitoids are not distributed
randomly among host groups, as host feeding type, body size,
etc. varies, and some parasitoids are more specialized than
others. For example, since ichneumonids are on average larger
than chalcids, only few ichneumonids can develop on very
small hosts (Hawkins, 1994). Consequently, parasitoid
22
communities of small insects (such as most leafminers) tend to
be dominated by chalcids (especially Eulophidae) (Askew &
Shaw, 1974). Most parasitoids are niche specialist that search for
hosts that have a particular feeding habit or that utilize a specific
plant part (Hawkins, 1994). Small eulophids that attack miners
are thought to use visual cues like mine shape or color for
finding their host (Salvo & Valladares, 2004). External-feeding
herbivores on average have fewer parasitoids than do internalfeeding species. However, parasitoid species richness varies
widely, and leafminers tend to be attacked by comparatively
high numbers of parasitoids (Hawkins, 1994).
Like other insect herbivores, sawflies are attacked by a
diverse community of parasitoids, and parasitoids may
compose a significant mortality factor for sawfly larvae
(Hawkins, 1994; Connor & Taverner, 1997; Kopelke, 1999).
Heterarthrine larvae are attacked by parasitoids from three
hymenopteran families (Ichneumonidae, Braconidae, and
Eulophidae). The varying preferences and diet breadths of these
enemy species (Pschorn-Walcher & Altenhofer, 1989) make
them an excellent study group for food-web studies. A very
similar situation occurs in the Euurina gallers: parasitoids and
parasitic inquilines constitute the main source of mortality in
many galler species (Kopelke, 1999; Roininen et al., 2002; Craig
et al., 2007), and the gall inducers collectively support a complex
of over 80 parasitoid and inquiline species from 16 families in
four insect orders (Roininen & Danell, 1997; Roininen et al.,
2002; Kopelke, 1999).
23
24
3. Materials and Methods
3.1 MATERIAL SAMPLING
Sawfly material for this thesis was provided by many
researchers, but mainly collected by T. Nyman. The leafminer
study (I) contained 39 heterarthrine species and 20 outgroup
species. Galler samples (II) were collected from two locations in
northern Fennoscandia (Kilpisjärvi in Finland and Abisko in
Sweden). Euura bud galls were collected in the year 1998 from
six willow species: Salix lanata, S. glauca, S. lapponum, S.
phylicifolia, S. myrsinifolia, and S. hastata. Leaf-galling Pontania
were collected in the years 1997 and 1998 from same willow
species, but also from S. borealis, S. reticulata, and S. myrsinites.
Parasitoid larvae (IV) were likewise collected from Kilpisjärvi
and Abisko, but also from Tromsø in Norway. Galls were
randomly collected in years 2009 and 2010 into plastic bags from
six boreal–subarctic willow species (Salix lanata, S. glauca, S.
lapponum, S. myrsinifolia, and S. phylicifolia) and from three
arctic–alpine dwarf willow species (S. reticulata, S. polaris, and S.
herbacea). In the laboratory, some of the galls were dissected
under a microscope in order to find out the fate of the sawfly
larva (live galler larva / galler killed by parasitoid / galler’s
cause of death unknown), and the rest of the galls were put into
glass jars in order to rear galler and parasitoid adults (Fig. 2).
25
Figure 2. Galler and parasitoid rearing jars with collection tubes. Leaves with
Pontania galls were put into glass jars having a sand layer of a few centimeters at the
bottom, and a thin layer of Sphagnum moss on top of the sand. In April, when the
rearing jars were taken to room temperature, they were covered with black plastic. The
lids of the jars were pierced with a silicone tube that led to a transparent plastic
collection tube. Emerging sawflies and parasitoids were attracted to the collection
heads by light entering the rearing jar via the silicone tube.
3.2 GENETIC MATERIAL
Details of DNA extraction, PCR amplification, and sequencing
can be found in Nyman et al. (2000), (2006b) and studies I, III,
and IV. In the leafminer study (I), we used two mitochondrial
genes, Cytochrome oxidase I (COI) and Cytochrome b (Cytb),
and two nuclear genes, Elongation factor-1α (EF-1α) and
Sodium-potassium adenosine triphosphatase (NAK). The
relatively fast-evolving mitochondrial COI and Cytb genes are
suitable for studying relatively recent speciation events, whereas
the “slower” exons of the nuclear EF-1α and NAK genes are
better suited for investigating older divergences (Lin &
Danforth, 2004; Whitfield & Kjer, 2008). The genus-level timecalibrated plant phylogeny used in the miner study (I) was
reconstructed using matK, 26S, 18S, rbcL, and atpB sequences
collected from the literature and GenBank. For gall-inducing
sawflies (II), we sequenced the mitochondrial COI gene and the
nuclear, fast-evolving ribosomal Internal transcribed spacer 2
(ITS2) region, which is easy to amplify and has enough
26
variability for studying closely related species (Coleman, 2003;
Yao et al., 2010). All sequences were read, and edited, and most
of them also aligned, using Sequencher 4.8 (Gene Codes Corp.,
Ann Arbor, MI). Because the lengths of Cytb and ITS2 sequences
differed among species, they were aligned using ClustalW
(Larkin et al., 2007).
In the galler parasitoid study (IV), parasitoid larvae were
identified based on standard DNA barcode methods (Hebert et
al., 2003). DNA barcoding rests on the idea that all organisms
can be identified using one or a few short sequence fragments.
In the case of animals, the standard barcode is a portion of the
mitochondrial COI gene (Hebert et al., 2003), which is relatively
easy to amplify and sequence, and usually has enough
differences for reliable identification of species (e.g., Hebert et
al., 2003; 2004; Hajibabaei et al., 2006; Dinca et al., 2010). Reared
parasitoid adults were identified by expert taxonomists, and
then sequenced in order to build a reference library, which
could be used for identifying larval samples. With the help of
the barcode database, we were able to use larval samples
without a need to rear parasitoids to adults. This facilitates the
identification process and reduces errors caused by
taxonomically variable mortality during rearing (Tilmon et al.,
2000; Agustí et al., 2005; Smith et al., 2006; 2007; 2008).
3.3 PHYLOGENY RECONSTRUCTION
Phylogenetic trees present evolutionary relationships among
organisms, illustrating how closely they are related based on
their genetic or physical characters (Lemey et al., 2009). There
are various methods to construct a phylogeny and every method
has its pros and cons, but none of them guarantee that the
obtained tree is the “true” phylogenetic tree. Basically, methods
can be divided into character-state and distance-matrix
methods, based on what kind of approach they use to analyze
the data. Simple distance-matrix methods such as UPGMA and
Neighbor-joining (NJ) are computationally fast and, thus,
27
suitable for large data sets (Lemey et al., 2009). An NJ tree was
calculated for gall-inducing sawflies based on combined data
(COI + ITS2), after removing specimens that did not have
sequences of both genes, in PAUP v. 4.0b10 (Swofford, 2003; II).
An NJ tree was also calculated for adult parasitoid sequences in
MEGA v. 5.1 (Tamura et al., 2011). Later, larval samples were
added to the dataset for larval identification, and a final NJ tree
was then calculated with only larval samples (IV).
Other methods commonly used for phylogeny reconstruction
are Maximum parsimony (MP), Maximum likelihood (ML), and
Bayesian methods. The idea behind MP is simple: the aim is to
find the tree or trees that require the least evolutionary change
(= smallest number of changes in characters) in the observed
data (Kluge & Farris, 1969; Fitch, 1971). In sequence analyses,
gaps can be treated as a fifth character, which is why MP was
used for analyzing ITS2 sequence data of gall-inducing sawflies
(II). Basic parsimony methods work well for small data sets
containing fewer than 100 taxa, but for larger data sets better
options are available, like Nixon’s (1999) parsimony ratchet
method, which was implemented in PAUPrat (Sikes & Lewis,
2001) in conjunction with PAUP (I; II). Ratchet searches are more
efficient in finding the most parsimonious tree than are heuristic
searches, by sampling more tree islands and collecting fewer
trees from each island than traditional methods (Nixon, 1999).
In model-based analyses, the best-fitting substitution model
has to be found for each gene before the analysis. Evolutionary
models are assumptions of nucleotide or amino acid
substitutions, and they describe the probabilities of change from
one nucleotide or amino acid to another in a phylogenetic tree
(Liò & Goldman, 1998; Lemey et al., 2009). Model selection was
performed in jModelTest v. 0.1.1 (Posada, 2008; I) and v. 2.1.3
(Darriba et al., 2012; II).
ML searches for the tree that has the highest likelihood of
producing the observed data given the tree topology, branch
lengths, and the selected model of evolution (Lemey et al., 2009).
In likelihood calculations, all possible nucleotide states are
summed in the ancestral nodes to obtain the tree, and the tree
28
with highest likelihood is chosen to be the best tree. ML trees
were calculated in RAxML v. 7.2.8 (Stamatakis et al., 2008; I; IV)
and PhyML v. 3.0 (Guindon et al., 2010; II).
Bayesian methods differ from MP and ML, as Bayesian
inference approaches do not attempt to find only one best tree
(Lemey et al., 2009). Bayesian methods search for plausible trees
using likelihood, with the researcher specifying prior beliefs and
an evolutionary model. Like for other tree construction methods,
there are multiple programs for Bayesian analyses, with
different focuses. Leafminer sequences (I) were analyzed using
MrBayes v. 3.1.2 (Ronquist & Huelsenbeck, 2003), which focuses
in phylogenetic inference, and in BEAST v. 1.5.2 (Drummond &
Rambaut, 2007), which aims at producing trees with a time
scale. BEAST was especially used to estimate diversification
times of leaf-mining sawflies and their host plants using a
Bayesian relaxed molecular-clock method. In the study on gallinducing sawflies (II), MrBayes v. 3.2.2 (Ronquist et al. 2012) was
used for CoI, ITS2 and the combinined data set (CoI + ITS2).
Before the analysis, gaps in ITS2 sequence had to be coded
present or absent using the method of Simmons and Ochoterena
(2000) in the program FastGap v. 1.2 (Borchsenius 2009).
The Pseudodineura phylogeny presented in this thesis (see
below) was calculated using COI, Cytb, EF-1α and NAK
sequences. RAxML was run at the CIPRES web portal (Miller et
al., 2010) with a separate GTR+G model for each data partition
(gene), and support for nodes were evaluated based on 100
bootstrap replicates.
3.4 INSECT–PLANT ANALYSES
After constructing phylogenies for sawflies and plants, it was
possible to compare them with each other. Contrasting the
phylogenetic trees of insects with those of their host plants can
show how these associations have evolved, for example, have
there been host shifts or has there been cospeciation (Jackson,
2004; Lopez-Vaamonde et al., 2003; Nyman, 2010; Wilson et al.,
29
2012; I). If plants and herbivores have cospeciated, then their
phylogenies should be mirror images of each other, and their
diversification times should be concurrent. Comparing
diversification times of insects and hosts provides valuable
information on insect radiation (Lopez-Vaamonde et al., 2006;
Gómez-Zurita et al., 2007; Ohshima et al., 2010; I). Insect
phylogenies can also be used to illustrate, for example,
evolution of larval feeding habits (I). Larval feeding and hostplant use were reconstructed in Mesquite using the “Trace
character over trees” option, with either parsimony or
maximum-likelihood optimization (Maddison & Maddison,
2010). Before the reconstruction, each miner was coded
according to its host-plant genera or larval feeding habit. An ML
tree was used in larval feeding reconstruction in the tree
including leaf-mining tribe Pseudodineura, which was
constructed using maximum-likelihood optimization (Fig. 3).
Genetic variation among and within populations can be
analyzed in ARLEQUIN v. 3.5 (Excoffier & Lischer, 2010). In the
galler study (II) we used ARLEQUIN to estimate pairwise ΦST
values among population samples collected from different hosts
and locations, and also performed a hierarchical analysis of
molecular variance (AMOVA) (Excoffier et al., 1992). These
analyses were performed separately for mitochondrial and
nuclear genes. Only the six willow species that were shared by
both galler genera were used. In the hierarchical AMOVAs, we
used two different grouping hierarchies: collection locations
within host species, and host species within locations. Statistical
significance of the variance components calculated from the
AMOVAs were determined with 10,000 permutations.
Comparisons of ΦST values across host-species pairs, and the
existence of a correlation between the Pontania and Euura
datasets were analyzed using a Mantel test in PC-ORD v. 5.0
(McCune and Mefford, 2006).
30
3.5 ANALYSES OF TRITROPHIC INTERACTIONS
One method to analyze tritrophic interactions is to use Ives and
Godfray's (2006) phylogenetic bipartite linear model (pblm),
which can be found in the picante v. 1.2 package (Kembel et al.,
2010) in R v. 2.10 (R Development Core Team 2009). Pblm was
used in studies III and IV, because the model can be used to
estimate how well ecological versus phylogenetic factors explain
parasitoid–insect associations. For this analysis, one has to
construct a phylogeny for all studied levels. A binary (parasitoid
present / absent) association matrix was constructed for 25
heterarthrine species for which information on parasitoids was
available (59 species) (Fig 2; III) (Pschorn-Walcher & Altenhofer,
1989; Digweed et al., 2009). A similar matrix was constructed for
seven galler species with 14 barcode-identified parasitoids, but
this time with quantitative data (IV). In the leafminer study (III),
we also created a “pseudophylogeny” for the miners based on
the host-plant phylogeny. First, plant species not used by miners
were removed from the full plant phylogeneny. Then miners
were added onto the tree according to their host genera,
maeaning thst miners using same plant genera as a host created
a polytomy. The signal-strength parameter (d) measures the
how well the phylogenetic trees explain associations: a value of
0 indicates absence of phylogenetic signal, values from 0 to 1
represent stabilizing selection, a value 1 conforms to the
Brownian-motion assumption, and values above 1 indicate that
the phylogenetic signal exceeds the Brownian-motion
assumption (Ives & Godfray, 2006). By comparing mean square
errors, one can evaluate the overall fit of the full model, in
which d parameters are estimated from the data (MSEd), in
relation to a model that assumes no phylogenetic covariances
(MSEstar) and to a model that assumes Brownian-motion
evolution (MSEb). Lower MSE values indicate a better fit of the
specific model. In both studies, 95% confidence intervals were
obtained by bootstrapping either 500 (III) or 1,000 (IV) times.
Several additional statistical analyses were performed in
study IV. Effects of host and location on rates of survival and
31
parasitism were tested with two-way ANOVA in IBM SPSS v. 21
(IBM SPSS statistics Inc. Chicago, IL, USA). In comparisons of
enemy species richness across community samples (galler ×
willow × location) and hosts (galler × willow), sampling effort
was standardized by constructing species-accumulation curves
in EstimateS v. 9.0.0 (Colwell, 2013). The effect of host species on
enemy-community richness was tested with a nonparametric
Kruskal–Wallis one-way ANOVA, and the effect of habitat with
a Mann–Whitney U-test in SPSS. Non-metric multidimensional
scaling (NMDS) ordination in PC-Ord v. 5.33 (McCune and
Mefford, 2006) was used to visualize parasitoid community
structure. Multi-response permutation procedures (MRPP) in
PC-Ord were used to test the effects of location, willow species,
and habitat (boreal–subarctic / arctic–alpine) on parasitoid
communities. Permutational multivariate analysis of variance
(PERMANOVA) in PRIMER v. 6.1.15 with the PERMANOVA+
v. 1.0.5 add-on package (Clarke & Gorley, 2006), was also used
to test the effects of host and location.
32
4. Results and Discussion
4.1 ROLE OF PLANTS IN INSECT SPECIATION
4.1.1 Leaf-mining sawflies
Leaf-mining has been thought to have evolved at least three
times in the sawfly family Tenthredinidae, i.e., in the tribes
Pseudodineurini (Nematinae), Fenusini (Blennocampinae), and
Heterarthrini (Heterarthrinae). However, there has been a
continuous debate over whether Fenusini in fact belongs to the
Heterarthrinae or not (Goulet, 1992; Pschorn-Walcher &
Altenhofer, 1989; Smith, 1971; Taeger et al., 2010). Some authors
have considered that the subfamily Heterarthrinae includes the
tribes Heterarthrini, Fenusini, and Caliroini, of which Caliroini
contains the leaf-skeletonizer genera Caliroa and Endelomyia
(Smith, 1971; Goulet, 1992; Viitasaari, 2002). By contrast, others
have proposed that heterarthrine leafminers are polyphyletic, so
that the habit of leaf-mining would have evolved independently
in the genus Heterarthrus and in the tribe Fenusini, of which the
latter would belong to the ecologically diverse subfamily
Blennocampinae (Pschorn-Walcher & Altenhofer, 1989). Our
phylogenetic analyses show that the heterarthrine leafminers
form a monophyletic group that evolved c. 100 million years ago
(I). Therefore, the traditional division to Fenusini and
Heterarthrini is clearly not correct, as Heterarthrus is grouped
inside the Fenusini (Fig. 3; I). The phylogenetic trees suggest that
Heterarthrinae as currently defined is a polyphyletic group,
because the leaf-skeletonizing genera Caliroa and Endelomyia are
not closely related to each other or to the leafminers. However, a
recent study with more genes shows that Caliroa and Endelomyia
are closely related, but are grouped together with externalfeeding blennocampines (Malm & Nyman, 2014).
Reconstructions of ancestral larval feeding modes indicate
that shifts from external to internal feeding (leaf-mining, gall
33
0.2
100
Scolioneura betuleti (6i)
Scolioneura vicina (S066)
Scolioneura tirolensis (2k)
Scolioneura sp. (S075)
Fenusella nana (S036)
100
Fenusella septentrionalis (3i)
100
Fenusella wuestneii (1i)
100
Fenusella hortulana (S033)
46
Fenusella glaucopis (S034)
83
Fenella nigrita (1j)
100
Fenusella sp. (5i)
63
Fenusa dohrnii (S038)
100
Fenusa pumila (S037)
39
Fenusa ulmi (4j)
54
Profenusa japonica (S073)
70
Parna reseri (9j)
100
Parna kamijoi (Xr)
99
Parna tenella (8i)
44
100
Hinatara sp. cf. excisa (2i)
Hinatara recta (9i)
96
Profenusa pygmaea (Xj)
100
Profenusa thomsoni (4k)
Profenusa lucifex (S064)
100 Heterathrus imbrosensis (S077)
100
Heterarthrus healyi (8k)
45
Heterarthrus aceris (S021)
100
Heterarthrus cuneifrons (S061)
78
74
Heterarthrus leucomela (9k)
49
Heterarthus nemoratus (P7)
100
Heterarthrus vagans (S022)
24
Heterarthrus microcephalus (S024)
Heterarthrus ochropoda (Xk)
79
100
100
Metallus lanceolatus (S063)
86
Metallus pumilus (S035)
100
45
Metallus rohweri (S074)
Metallus albipes (4i)
100
Notofenusa sp. (Xi)
8
Notofenusa surosa (3k)
14
Phymatocera aterrima (P4)
Silliana lhommei (S082)
18
24
Caliroa sp. (N7)
Hoplocampoides xylostei (S039)
84
Ardis brunniventris (N8)
51
94
Periclista sp. (S080)
22
Blennocampa phyllocolpa (S026)
Endelomyia aethiops (MX)
49
Siobla ruficornis (S040)
93
18
Tenthredo notha (L1)
Pachyprotasis rapae (S030)
16
73
Nesoselandria morio (S079)
Strongylogaster tacita (P8)
Athalia circularis (D2)
59
Priophorus pallipes (K6)
100
Trichiocampus aeneus (J7)
42
Cladius comari (JX)
79
Susana annulata (H8)
100
48
Hoplocampa marlatti (J5)
Hoplocampa oregonensis (G3)
Craterocercus fraternalis (G7)
97
Eitelius gregarius (E4)
35
100
Pontania pustulator (AX)
Euurina
92
Amauronematus amplus (A5)
100
Mesoneura opaca (G6)
Pristiphora erichsonii (K7)
71
100
Stauronematus
platycerus
(7s)
14
Stauronematus compressicornis (E5)
53
100
Hemichroa crocea (J8)
56
Hemichroa australis (1s)
Platycampus luridiventris (K2)
39
100
Hemicroa militaris cf. militaris (LX)
Hemichroa militaris cf. thoracicus (P1)
23
95
Dineura pullior (4s)
100
Nematinus steini (2s)
100
Nematinus acuminatus (H3)
Fallocampus americanus (P2)
31
Anoplonyx apicalis (H1)
66
Pseudodineura parvula (S225)
88 Pseudodineura heringi (6s)
100
Pseudodineura parvula (S227)
Pseudodineura parvula (S226)
69
85 Pseudodineura enslini (5s)
100
100
Pseudodineura enslini (S220)
24
Pseudodineura enslini (S219)
35
100
Pseudodineura mentiens (S224)
Pseudodineura mentiens (6r)
35
100
Pseudodineura parva (N5)
Pseudodineura parva (S228)
52
Pseudodineurini
100 Pseudodineura clematidis (S216)
100
Pseudodineura clematidis (S215)
100
100
Pseudodineura clematidisrectae (S218)
Pseudodineura clematidisrectae (S217)
100 Pseudodineura fuscula (S222)
91
100 Pseudodineura fuscula (S221)
87
100
Pseudodineura fuscula (S223)
Pseudodineura fuscula (J2)
100
100
Endophytus anemones (S229)
Endophytus anemones (N4)
32
Kerita fidala (4r)
67
100
Caulocampus acericaulis (F7)
Caulocampus matthewsi (J6)
55
Eriocampa ovata (N9)
Empria fletcheri (S069)
100
Abia candens (L2)
Trichiosoma aenescens (S090)
Diprion similis (L4)
81
Arge sp. (S086)
93
Sterictiphora sp. (M8)
Lophyrotoma analis (S084)
Blasticotoma filiceti (S085)
Larval feeding habit
External feeder
Leaf miner
Gall inducer
Shoot borer
Leaf roller
Fruit miner
Petiole miner
53
100
94
100
Heterarthrinae
0.2
Figure 3. Phylogeny of leaf-mining sawflies from the subfamily Heterarthrinae and the
nematine tribe Pseudodineurini. Selected outgroup taxa are from Tenthredinidae and
five other tenthredinoid families (see inset for full branch lengths). Numbers above
branches are bootstrap proportions (%) from a maximum-likelihood analysis in
RAxML. Branch colors show ancestral larval feeding habits reconstructed using ML
optimization. Nodes and branches were colored with a particular state (see legend)
when the likelihood of the most likely larval feeding habit for the node exceeded 99 %,
otherwise a pie chart is given for the node. An arrow shows the place of Euurina
species, which were used in studies II and IV.
induction, shoot-boring, and leaf-rolling) have occurred several
times in the Tenthredinoidea (Fig. 3; I). Within Tenthredinidae,
two shifts from external feeding to leaf-mining have taken place,
in the Heterarthrinae and in the tribe Pseudodineurini. All
Pseudodineura samples cluster with representatives of the
subfamily Nematinae, and the ancestral-state reconstruction
34
confirms that the leaf-mining habit arose independently in
Pseudodineura.
Heterarthrine species are said to be very specific in their use
of host plants (Altenhofer, 2003; Smith, 1979; Taeger &
Altenhofer, 1998). However, our phylogeny-based analyses
indicate that host-plant use in the group has not been stable on
longer time scales, because multiple shifts to distantly related
plant lineages have occurred (I). Comparing the miner and plant
phylogenies shows that the miners have radiated after their host
plants, because most of the miner nodes are younger than
corresponding nodes in the phylogenetic tree of their host
plants. Our miner results join an increasing group of studies that
have shown that diversification times of herbivore insects
postdate those of their host plants (Lopez-Vaamonde et al., 2006;
Gómez-Zurita et al., 2007; Hunt et al., 2007; McKenna et al.,
2009; Ohshima et al., 2010). Heterarthrine host shifts often occur
among few plant genera (mainly Betula, Alnus, Salix, and
Populus) that are not closely related, and this pattern likewise
shows similarities with other herbivore insect studies (LopezVaamonde et al., 2003; Nyman et al., 2006a; 2010; Scheffer et al.,
2007; Mardulyn et al., 2011). The frequent shifts among plant
taxa provide evidence that host plants have a major role in
diversification of herbivorous insects, and thus can drive
herbivore specialization onto alternative host plants (Ehrlich &
Raven, 1964; Winkler & Mitter, 2008; Fordyce, 2010; Slove &
Janz, 2011).
4.1.2 Gall-inducing sawflies
Our phylogenetic analyses revealed clear clustering of
individuals based on willow host species in both Pontania and
Euura (II), but there were no cases in which all specimens from a
single willow species would have formed a monophyletic
group. However, individuals from the same host were more
likely to cluster together than with specimens from other host
species. There are conflicts between the COI and ITS2 trees,
which may result from of interbreeding if the species are not
completely reproductively isolated from each other.
35
Hybridization and introgression is often found in insect
herbivores (Gompert et al., 2008; Linnen & Farrell, 2007;
Mardulyn et al., 2011; Marshall et al., 2011). Euura bud gallers
form at least three clear clusters (S. lapponum, S. lanata + S.
glauca, and S. phylicifolia + S. myrsinifolia) (Nyman, 2002)(II).
However, the results also suggest that Euura individuals using
S. hastata as a host form their own species, which would
conform to E. hastatae in the sense of Malaise (1920). Pontania
individuals using S. myrsinifolia and S. borealis are intermixed in
the trees, which questions the decision to divide leaf gallers on
these willows into two species (P. varia and P. norvegica,
respectively) as suggested by Kopelke (1999). Overall, the
phylogenies and AMOVA results (II; Tables 2 & 3) indicate that
host plant has a greater influence on genetic differentiation in
gall-inducing sawflies than does geographic region (II). This
result resembles findings of several previous studies
(Drummond et al., 2010; Stireman et al., 2012).
It has been suggested that endophagy promotes HAD, as
internal-feeding insects have very close connection with their
hosts (Stireman et al., 2005; Dorchin et al., 2009; Dickey &
Medina, 2012). Interactions between gall-makers and plants are
intensive, as the insects have to manipulate plant tissues to
produce the gall that they feed on. These hypotheses seem
plausible, because HAD has been found in gall-inducing
sawflies (II), gall midges (Stireman et al., 2005; Dorchin et al.,
2009), gall-making flies (Stireman et al., 2005), and galling pecan
leaf phylloxera (Dickey & Medina, 2012). However, more
studies are needed from different feeding guilds to confirm this.
Most studies on HAD have been done based on single insect
taxa and their hosts (Via et al., 2000; Peccoud et al., 2009;
Dorchin et al., 2009; Hernández-Vera et al., 2010). While there
are a few studies that have broadened their focus to involve
several insect and plant groups (Stireman et al., 2005; Dickey &
Medina, 2010; Egan et al. 2013; II), the repeatability of HAD has
not been studied much. Although Pontania and Euura gallers
share many willow host species, they are not sister taxa
(Nyman, 2000; 2007). Given that their evolutionary
36
opportunities have been quite similar, it could be expected that
their speciation patterns would also be similar. However, ΦST
estimates in these galler groups reveal that differentiation in
nuclear ITS2 is higher in Pontania than in Euura, while the
average levels of differentiation in mitochondrial COI are almost
the same in both taxa (II). Comparing ΦST estimates across
shared willow host species in the Pontania and Euura samples
revealed no evidence of a correlation in the level of HAD in
either of the genes used. Even though these galler genera live in
a similar niche environment consisting of Salix species, they
differ in how they experience their host species. Reasons for this
could include, for example, different chemistry in leaves versus
buds, and in the phenological availability of these tissues. In
general, our results indicate that Euura and Pontania gallers fall
somewhere between host races and fully independent species
(Drès & Mallet, 2002; Peccoud et al., 2009; Powell et al., 2013), as
species boundaries are not completely developed. Evolution
does not seem to follow the same path even when
environmental circumstances are very similar.
4.3 TRITROPHIC INTERACTIONS
4.3.1 The parasitoid community of leaf-mining sawflies
Heterarthrine leafminers are attacked by numerous
hymenopteran parasitoids, but they have lost most of the
hymenopteran, and all dipteran, parasitoids that live on
external-feeding sawflies (Price & Pschorn-Walcher, 1988;
Pschorn-Walcher & Altenhofer, 1989; Richter & Kasparyan,
2013). Some of the parasitoids are polyphagous (e.g., Colastes
braconius Haliday), and several Pnigalio and Chrysocharis species
even use also other leaf-mining insect taxa as hosts (Godfray,
1994; Noyes, 2013). Ichneumonids tend to be more specialized
than other parasitoids (Pschorn-Walcher & Altenhofer, 1989),
and, in heterarthrine miners, three specialized ichneumonid
parasitoids inflicted the highest mortality (III). However, none
of the parasitoid species on heterarthrines are closely related to
37
each other (Quicke et al., 2009). Thus, it seems that the miner
enemy complex has evolved gradually, as the parasitoids
represent three families that are widely separated in the
phylogenies, and also are shared with other herbivore taxa
(Gauthier et al., 2000; Zaldivar-Riverón et al., 2006; Pitz et al.,
2007; Quicke et al., 2009;). In Heterarthrinae, closely related
parasitoids tend to attack the same miner species, and the
situation therefore differs from the study by Ives & Godfray
(2006) on leaf-mining Phyllonorycter moths and their enemies.
The different results may arise from our wider taxon sampling,
because the taxonomic scale may influence the phylogenetic
signal arising from the hosts and parasitoids (Cagnolo et al.,
2011; Desneux et al., 2012).
There are few studies indicating that diversification can
cascade, meaning that diversification of plants leads to
diversification
of
herbivores,
which
then
promotes
diversification of parasitoids (Cronin & Abrahamson, 2001;
Althoff, 2008). The focal plants, leaf-mining sawflies, and
parasitoids provided good opportunities for studying “bottom–
up” and “top–down” diversification forces in multitrophic
networks. In miners, the presence of specialized ichneumonids
indicates that some “bottom–up” diversification might have
happened in parasitoids following heterarthrine host shifts (III).
Nevertheless, the existence of many polyphagous eulophid and
braconid species makes things more complex. Even though the
possibility exists that some of the presumed generalists are
cryptic specialists (cf. Smith et al., 2006; Smith et al., 2007;
Kaartinen et al., 2010; Hayward et al., 2011), it seems that
“bottom–up”
processes
cannot
completely
explain
diversification in this system. Phylogeny-based analyses of
miner–parasitoid associations indicate that host plants have a
stronger influence on these associations than does the
phylogeny of the miner species (III). If parasitoids are herbivore
niche specialists, they could influence insect diversification if the
herbivores can find enemy-free space on novel plant species
(Bernays & Graham, 1988; Lill et al., 2002; Singer & Stireman,
2005). As there are niche- and species-specialist enemies in this
38
system, both diversifying forces appear to have played a role.
As in other tritrophic food webs, associations among plants,
heterarthrine miners, and parasitoids have evolved through
multiple complex mechanisms, which involved host shifts in
both miners and parasitoids (Lopez-Vaamonde et al., 2005;
Zaldívar-Riverón et al., 2008).
4.3.2 The parasitoid community of gall-inducing sawflies
Lately, molecular methods have become more popular also in
studies on multitrophic systems. Identification of parasitoids
based on morphology can be very slow and demanding and,
hence, cryptic species are often found when molecular methods
are used (Smith et al., 2006; 2008; 2011; Hayward et al., 2011;
Gebiola et al., 2012). Also rearing can give unreliable results,
especially if rearing success is low. In gallers, our reared adults
grouped into 18 distinct clusters based on their DNA barcode
sequences, and nearly all larval parasitoids could be indentified
to species level based on the reference dataset (IV). These results,
along with a growing body of other studies, indicate that DNA
barcoding is an efficient tool for parasitoid community studies,
and for indentifying species when morphological identification
is difficult (Smith et al., 2006; 2008; 2011; Kaartinen et al., 2010;
Wirta et al., 2014). However, the possibility exists that
endoparasitoids were lost during larval collecting, as we only
stored visible parasitoid eggs, pupae, and larvae. This may have
a small influence on the obtained results, but it most likely
would not change the overall pattern that we found. The enemy
community of Pontania gallers contained eight common species,
and six species that were encountered only a few times each (IV).
All of the common parasitoids use multiple galler species as
hosts, but our NDMS ordination analyses revealed clear and
statistically significant differences in the enemy communities on
different galler and willow species, as well as a strong effect of
galler habitat (boreal–subarctic vs. arctic–alpine). A two-way
PERMANOVA also found a relatively weak, but statistically
significant, effect for location.
39
Parasitoids and parasitic inquilines are the most important
mortality factor in many galler species (Kopelke, 1999; Roininen
et al., 2005; Craig et al., 2007) and, thus, escape from enemies
could provide a huge selective advantage. If parasitoids use
herbivore niches (e.g., plant species or feeding type / tissue
type) as cues for finding the herbivores, then parasitoids could
promote herbivore speciation. The observed strong effect of
habitat on leaf-galler parasitoid communities indicates that, in
addition to host-plant shifts, entering a new habitat may
provide shelter for herbivores, and thereby accelerate herbivore
speciation (IV). Parasitoids have a close connection to their host
and are often host specific (Godfray, 1994; Condon et al., 2014).
Thus host phylogeny might influence parasitoid speciation, and
parasitoids could speciate in parallel with their hosts. However,
phylogenetic studies indicate that the phylogenies of herbivores
have relatively little influence on insect–parasitoid associations
(Ives & Godfray, 2006; III; IV; but see Deng et al., 2013).
Host shifts could also be an important factor influencing
parasitoid diversification. A few studies have managed to show
that HAD can cascade across trophic levels in plant–herbivore–
parasitoid systems (Stireman et al., 2006; Forbes et al., 2009;
Feder & Forbes, 2010), but others have not found HAD in
insect–parasitoid associations (Cronin & Abrahamson, 2001;
Althoff, 2008; Bilodeau et al., 2013). In our study (IV), the largest
difference in enemy communities was found between galler
species that inhabit the boreal–subarctic vs. arctic–alpine zones
in the study areas. Thus, it seems that galler shifts into arctic–
alpine habitats have led to speciation in at least two parasitoid
groups, suggesting that habitat shifts could accelerate parasitoid
diversification. When a herbivore escapes its enemies onto a
novel plant species, parasitoids that manage to track the shift
have to face a new environment with novel plant volatiles and
morphology in order to find their hosts. They also have to
overcome novel plant toxins ingested by the herbivores.
Overcoming these obstacles may create divergent selection
pressures in the parasitoids and promote HAD (Stireman et al.,
2006). As parasitoids may be a driving force in herbivore
40
speciation, then parasitoids could catch up herbivores on novel
plant species by forming host races, which may lead to further
shifts in the herbivores. Such repeated host-associated shifts
may partly explain the extreme species diversity in these
interactions.
41
42
5 Conclusions
This thesis presents new information on the role of host plants
in speciation of herbivore insects and their parasitoids. Insect–
plant interactions are taxonomically unstable, and host shifts to
closely related plant species are common. As found in miners,
herbivores have usually radiated after their host plants. Thus,
current insect–plant interactions have evolved on a background
of already existing plant lineages that the miners have
colonized, and a few of them have changed host plants at some
point during their evolutionary history. Results from gallinducing sawflies likewise indicate that host plants have a
central role in herbivore speciation. Although HAD was found
in both galler genera, there are differences in how the two galler
taxa use their Salix host species. Evidently, the build-up of HAD
is not repeatable, even though evolutionary opportunities for
HAD and speciation have been similar in the focal galler
groups.
DNA barcoding is powerful tool for resolving the structure of
parasitoid complexes when species identification is difficult
based on morphology. Some parasitoids are species and others
niche specialists, indicating that these associations are complex,
and that both “bottom–up” and “top–down” diversification
forces have played a role in the studied networks. Host-plant
shifts could also affect parasitoid speciation, if parasitoids use
plants as cues to find their host. At least in the studied subarctic
and arctic–alpine habitats, habitat shifts in gallers have led to
speciation in two parasitoid groups, and thus the habitat shift
seems to have influenced parasitoid diversification. Our finding
that
both
leafminer–parasitoid
and
galler–parasitoid
associations are strongly influenced by the herbivore niches
indicates that parasitoids have the potential to spun herbivore
insect speciation by driving them into “enemy free space”
provided by novel hosts and/or habitats.
43
44
6 References
Abrahamson WG, Blair CP, Eubanks MD & Morehead SA (2003)
Sequential radiation of unrelated organisms: the gall fly
Eurosta solidaginis and the tumbling flower beetle
Mordellistena convicta. Journal of Evolutionary Biology 16:781–
789.
Agosta SJ (2006) On ecological fitting, plant-insect associations,
herbivore host shifts, and host plant selection. Oikos 114:556–
565.
Agosta SJ, Janz N & Brooks DR (2010) How specialists can be
generalists: resolving the" parasite paradox" and implications
for emerging infectious disease. Zoologia 27:151–162.
Agustí N, Bourguet D, Spataro T, Delos M, Eychenne N, Folcher
L & Arditi R (2005) Detection, identification and geographical
distribution of European corn borer larval parasitoids using
molecular markers. Molecular Ecology 14:3267–74.
Altenhofer E (2003) Minierende blattwespen (Hym.: Symphyta):
ihre minenformen, wirtspflanzen, ökologie und biologie.
Gredleriana 5–24.
Althoff DM (2008) A test of host-associated differentiation
across the 'parasite continuum' in the tri-trophic interaction
among yuccas, bogus yucca moths, and parasitoids. Molecular
Ecology 17:3917–3927.
Althoff DM, Segraves KA & Johnson MT (2014) Testing for
coevolutionary diversification: linking pattern with process.
Trends in Ecology and Evolution 29:82–89.
Argus GW (1997) Infrageneric classification of Salix (Salicaceae)
in the new world. Systematic Botany Monographs 52:1–121.
Askew RR & Shaw MR (1974) An account of the Chalcidoidea
(Hymenoptera) parasitising leaf-mining insects of deciduous
trees in Britain. Biological Journal of the Linnean Society 6:289–
335.
45
Berlocher SH & Feder JL (2002) Sympatric speciation in
phytophagous insects: moving beyond controversy? Annual
Review of Entomology 47:773–815.
Bernays E & Graham M (1988) On the evolution of host
specificity in phytophagous arthropods. Ecology 69:886–892.
Bilodeau E, Simon J-C, Guay J-F, Turgeon J & Cloutier C (2013)
Does variation in host plant association and symbiont
infection of pea aphid populations induce genetic and
behaviour differentiation of its main parasitoid, Aphidius ervi?
Evolutionary Ecology 27:165–184.
Boevé JL, Sonet G, Nagy ZT, Symoens F, Altenhofer E,
Häberlein C & Schulz S (2009) Defense by volatiles in leafmining insect larvae. Journal of Chemical Ecology 35:507–517.
Borchsenius
F
(2009)
FastGap
1.2.
Available
at:
http://www.aubot.dk/FastGap_home.htm.
Cagnolo L, Salvo A & Valladares G (2011) Network topology:
patterns and mechanisms in plant-herbivore and hostparasitoid food webs. Journal of Animal Ecology 80:342–351.
Clarke KR & Gorley RN (2006) PRIMER v6: User
Manual/Tutorial. PRIMER-E, Plymouth.
Coleman AW (2003) ITS2 is a double-edged tool for eukaryote
evolutionary comparisons. Trends in Genetics 19:370–375.
Colwell RK (2013) Estimate S: Statistical estimation of species
richness and shared species from samples. Version 9 or
earlier.
User's
guide
and
application.
http://viceroy.eeb.uconn.edu/estimates/index.html.
Condon MA, Scheffer SJ, Lewis ML, Wharton R, Adams DC &
Forbes AA (2014) Lethal interactions between parasites and
prey increase niche diversity in a tropical community. Science
343:1240–1244.
Connor EF & Taverner MP (1997) The evolution and adaptive
significance of the leaf-mining habit. Oikos 79:6–25.
Cook LG & Gullan PJ (2004) The gall-inducing habit has evolved
multiple times among the eriococcid scale insects
(Sternorrhyncha: Coccoidea: Eriococcidae). Biological Journal
of the Linnean Society 83:441–452.
46
Craig TP, Itami JK & Horner JD (2007) Geographic variation in
the evolution and coevolution of a tritrophic interaction.
Evolution 61:1137–1152.
Crespi BJ, Carmean DA & Chapman TW (1997) Ecology and
evolution of galling thrips and their allies. Annual Review of
Entomology 42:51–71.
Cronin JT & Abrahamson WG (2001) Do parasitoids diversify in
response to host-plant shifts by herbivorous insects?
Ecological Entomology 26:347–355.
Darriba D, Taboada GL, Doallo R & Posada D (2012) jModelTest
2: more models, new heuristics and parallel computing.
Nature Methods 9:772–772.
Davis RB, Baldauf SL & Mayhew PJ (2010) The origins of species
richness in the Hymenoptera: insights from a family-level
supertree. BMC Evolutionary Biology 10:109.
De Moraes CM, Lewis WJ, Pare PW, Alborn HT & Tumlinson JH
(1998)
Herbivore-infested
plants
selectively
attract
parasitoids. Nature 393:570–573.
De Moraes CM & Mescher MC (2004) Biochemical crypsis in the
avoidance of natural enemies by an insect herbivore.
Proceedings of the National Academy of Sciences of the USA
101:8993–8997.
Deng J, Yu F, Li H-B, Gebiola M, Desdevises Y, Wu S-A &
Zhang Y-Z (2013) Cophylogenetic relationships between
Anicetus parasitoids (Hymenoptera: Encyrtidae) and their
scale insect hosts (Hemiptera: Coccidae). BMC Evolutionary
Biology 13:275.
Desneux N, Blahnik R, Delebecque CJ & Heimpel GE (2012)
Host phylogeny and specialisation in parasitoids. Ecology
Letters 15:453–460.
Dickey AM & Medina RF (2010) Testing host-associated
differentiation in a quasi-endophage and a parthenogen on
native trees. Journal of Evolutionary Biology 23:945–56.
Dickey AM & Medina RF (2012) Host-associated genetic
differentiation in pecan leaf phylloxera. Entomologia
Experimentalis et Applicata 143:127–137.
47
Digweed SC, MacQuarrie CJK, Langor DW, Williams DJM,
Spence JR, Nystrom KL & Morneau L (2009) Current Status
of invasive alien birch-leafmining sawflies (Hymenoptera:
Tenthredinidae) in Canada, with keys to species. Canadian
Entomologist 141:201–235.
Dinca V, Zakharov EV, Hebert PD & Vila R (2010) Complete
DNA barcode reference library for a country's butterfly fauna
reveals high performance for temperate Europe. Proceedings
of the Royal Society B: Biological Sciences 278:347–355.
Dorchin N, Scott ER, Clarkin CE, Luongo MP, Jordan S &
Abrahamson WG (2009) Behavioural, ecological and genetic
evidence confirm the occurrence of host-associated
differentiation in goldenrod gall-midges. Journal of
Evolutionary Biology 22:729–739.
Drès M & Mallet J (2002) Host races in plant-feeding insects and
their importance in sympatric speciation. Philosophical
Transactions of the Royal Society B: Biological Sciences 357:471–
92.
Drummond AJ & Rambaut A (2007) BEAST: Bayesian
evolutionary analysis by sampling trees. BMC Evolutionary
Biology 7:214.
Drummond CS, Xue HJ, Yoder JB & Pellmyr O (2010) Hostassociated divergence and incipient speciation in the yucca
moth Prodoxus coloradensis (Lepidoptera: Prodoxidae) on
three species of host plants. Heredity 105:183–196.
Egan SP, Hood GR, DeVela G & Ott JR (2013) Parallel patterns of
morphological and behavioral variation among hostassociated populations of two gall wasp species. PLoS ONE
8:e54690.
Ehrlich PR & Raven PH (1964) Butterflies and plants: a study in
coevolution. Evolution 18:586–608.
Excoffier L & Lischer HE (2010) Arlequin suite ver 3.5: a new
series of programs to perform population genetics analyses
under Linux and Windows. Molecular Ecology Resources
10:564–567.
Excoffier L, Smouse PE & Quattro JM (1992) Analysis of
molecular variance inferred from metric distances among
48
DNA haplotypes: application to human mitochondrial DNA
restriction data. Genetics 131:479–491.
Farrell BD (1998) "Inordinate fondness" explained: why are there
so many beetles? Science 281:555–559.
Farrell BD (2001) Evolutionary assembly of the milkweed fauna:
cytochrome oxidase I and the age of Tetraopes beetles.
Molecular Phylogenetic and Evolution18:467–78.
Farrell BD, Dussourd DE & Mitter C (1991) Escalation of plant
defense: do latex and resin canals spur plant diversification?
American Naturalist 138:881–900.
Feder JL & Forbes AA (2010) Sequential speciation and the
diversity of parasitic insects. Ecological Entomology 35:67–76.
Fitch WM (1971) Toward defining the course of evolution:
minimum change for a specific tree topology. Systematic
Biology 20:406–416.
Forbes AA, Powell TH, Stelinski LL, Smith JJ & Feder JL (2009)
Sequential sympatric speciation across trophic levels. Science
323:776–779.
Fordyce JA (2010) Host shifts and evolutionary radiations of
butterflies. Proceedings of the Royal Society B: Biological Sciences
277:3735–3743.
Funk DJ, Filchak KE & Feder JL (2002) Herbivorous insects:
model systems for the comparative study of speciation
ecology. Genetica 116:251–267.
Gauthier N, Lasalle J, Quicke DLJ & Godfray HCJ (2000)
Phylogeny of Eulophidae (Hymenoptera: Chalcidoidea), with
a reclassification of Eulophinae and the recognition that
Elasmidae are derived eulophids. Systematic Entomology
25:521–539.
Gebiola M, Gómez-Zurita J, Monti MM, Navone P & Bernardo U
(2012) Integration of molecular, ecological, morphological
and endosymbiont data for species delimitation within the
Pnigalio soemius complex (Hymenoptera: Eulophidae).
Molecular Ecology 21:1190–1208.
Godfray HC (1994) Parasitoids: Behavioral and Evolutionary
Ecology. Princeton University Press, Princeton.
49
Gompert Z, Forister ML, Fordyce JA & Nice CC (2008)
Widespread mito-nuclear discordance with evidence for
introgressive hybridization and selective sweeps in Lycaeides.
Molecular Ecology 17:5231–44.
Goulet H (1992) The genera and subgenera of the sawflies of
Canada and Alaska (Hymenoptera: Symphyta). Insects and
Arachnids of Canada 20:1–235.
Goulet H & Huber JT (1993) Hymenoptera of the World: An
Identification Guide to Families. Research Branch Agriculture
Canada Publication, Ottawa, Ontario.
Gómez-Zurita J, Hunt T, Kopliku F & Vogler AP (2007)
Recalibrated tree of leaf beetles (Chrysomelidae) indicates
independent diversification of angiosperms and their insect
herbivores. PLoS ONE 2:e360.
Guindon S, Dufayard J-F, Lefort V, Anisimova M, Hordijk W &
Gascuel O (2010) New algorithms and methods to estimate
maximum-likelihood phylogenies: assessing the performance
of PhyML 3.0. Systematic Biology 59:307–321.
Hajibabaei M, Janzen DH, Burns JM, Hallwachs W & Hebert PD
(2006) DNA barcodes distinguish species of tropical
Lepidoptera. Proceedings of the National Academy of Sciences of
the USA 103:968–971.
Hardy NB & Cook LG (2010) Gall-induction in insects:
evolutionary dead-end or speciation driver? BMC
Evolutionary Biology 10:257.
Hawkins BA (1994) Pattern and Process in Host-parasitoid
Interactions. Cambridge University Press, Cambridge.
Hayward A, McMahon DP & Kathirithamby J (2011) Cryptic
diversity and female host specificity in a parasitoid where the
sexes utilize hosts from separate orders. Molecular Ecology
20:1508–1528.
Hebert PD, Cywinska A, Ball SL & deWaard JR (2003) Biological
identificaions through DNA barcodes. Proceedings of the Royal
Society B: Biological Sciences 270:313–321.
Hebert PD, Penton EH, Burns JM, Janzen DH & Hallwachs W
(2004) Ten species in one: DNA barcoding reveals cryptic
species in the neotropical skipper butterfly Astraptes
50
fulgerator. Proceedings of the National Academy of Sciences of the
USA 101:14812–14817.
Hendry AP, Huber SK, De León LF, Herrel A & Podos J (2009)
Disruptive selection in a bimodal population of Darwin's
finches Proceedings of the Royal Society B: Biological Sciences
276:753–759.
Hernández-Vera G, Mitrović M, Jović J, Tosevski I, Caldara R,
Gassmann A & Emerson BC (2010) Host-associated genetic
differentiation in a seed parasitic weevil Rhinusa antirrhini
(Coleptera: Curculionidae) revealed by mitochondrial and
nuclear sequence data. Molecular Ecology 19:2286–2300.
Hespenheide HA (1991) Bionomics of leaf-mining insects.
Annual Review of Entomology 36:535–560.
Hrcek J, Miller SE, Quicke DL & Smith MA (2011) Molecular
detection of trophic links in a complex insect host-parasitoid
food web. Molecular Ecology Resources 11:786–794.
Hunt T, Bergsten J, Levkanicova Z, Papadopoulou A, John OS,
Wild R, Hammond PM, Ahrens D, Balke M, Caterino MS,
Gómez-Zurita J, Ribera I, Barraclough TG, Bocakova M,
Bocak L & Vogler AP (2007) A comprehensive phylogeny of
beetles reveals the evolutionary origins of a superradiation.
Science 318:1913–1916.
Ives AR & Godfray HC (2006) Phylogenetic analysis of trophic
associations. American Naturalist 168:E1–E14.
Jackson AP (2004) Cophylogeny of the Ficus microcosm.
Biological Reviews 79:751–768.
Janz N (2011) Ehrlich and Raven revisited: mechanisms
underlying codiversification of plants and enemies. Annual
Review of Ecology, Evolution, and Systematics 42:71–89.
Janz N & Nylin S (1998) Butterflies and plants: a phylogenetic
study. Evolution 486–502.
Kaartinen R, Stone GN, Hearn J, Lohse K & Roslin T (2010)
Revealing secret liaisons: DNA barcoding changes our
understanding of food webs. Ecological Entomology 35:623–
638.
Kembel SW, Cowan PD, Helmus MR, Cornwell WK, Morlon H,
Ackerly DD, Blomberg SP & Webb CO (2010) Picante: R tools
51
for integrating phylogenies and ecology. Bioinformatics
26:1463–1464.
Kergoat GJ, Silvain JF, Delobel A, Tuda M & Anton KW (2007)
Defining the limits of taxonomic conservatism in host-plant
use for phytophagous insects: molecular systematics and
evolution of host-plant associations in the seed-beetle genus
Bruchus Linnaeus (Coleoptera: Chrysomelidae: Bruchinae).
Molecular Phylogenetics and Evolution 43:251–269.
Kitching RL (2006) Crafting the pieces of the diversity jigsaw
puzzle. Science 313:1055–1057.
Kluge AG & Farris JS (1969) Quantitative phyletics and the
evolution of anurans. Systematic Biology 18:1–32.
Kopelke JP (1999) Gallenerzeugende blattwespen Europas:
taxonomische
grundlagen,
biologie
und
ökologie
Tenthredinidae: Nematinae: Euura, Phyllocolpa, Pontania).
Courier Forschungsinstitut Senckenberg 212:1–183.
Kopelke JP (2003) Gall-forming Nematinae, their willow hosts
(Salix spp.) and biological strategies (Insecta, Hymenoptera,
Symphyta, Tenthredinidae, Nematinae: Euura, Phyllocolpa,
Pontania). Senckenbergiana Biologica 82:163–190.
Labandeira CC & Phillips TL (1996) A Carboniferous insect gall:
insight into early ecologic history of the Holometabola.
Proceedings of the National Academy of Sciences of the USA
93:8470–8474.
Larkin MA, Blackshields G, Brown NP, Chenna R, McGettigan
PA, McWilliam H, Valentin F, Wallace IM, Wilm A, Lopez R,
Thompson JD, Gibson TJ & Higgins DG (2007) Clustal W and
Clustal X version 2.0. Bioinformatics 23:2947–2948.
Lemey P, Salemi M & Vandamme A (2009) The Phylogenetic
Handbook. A Practical Approach to Phylogenetic Analysis and
Hypothesis Testing. Cambridge University Press, Cambridge,
United Kindom.
Lill JT, Marquis RJ & Ricklefs RE (2002) Host plants influence
parasitism of forest caterpillars. Nature 417:170–173.
Lin C-P & Danforth BN (2004) How do insect nuclear and
mitochondrial gene substitution patterns differ? Insights
52
from Bayesian analyses of combined datasets. Molecular
Phylogenetics and Evolution 30:686–702.
Linnen CR & Farrell BD (2007) Mitonuclear discordance is
caused by rampant mitochondrial introgression in Neodiprion
(Hymenoptera: Diprionidae) sawflies. Evolution 61:1417–1438.
Liò P & Goldman N (1998) Models of molecular evolution and
phylogeny. Genome Research 8:1233–1244.
Lopez-Vaamonde C, Godfray HC & Cook JM (2003)
Evolutionary dynamics of host-plant use in a genus of leafmining moths. Evolution 57:1804–1821.
Lopez-Vaamonde C, Godfray HC, West SA, Hansson C & Cook
JM (2005) The evolution of host use and unusual
reproductive strategies in Achrysocharoides parasitoid wasps.
Journal of Evolutionary Biology 18:1029–1041.
Lopez-Vaamonde C, Wikström N, Labandeira C, Godfray HC,
Goodman SJ & Cook JM (2006) Fossil-calibrated molecular
phylogenies reveal that leaf-mining moths radiated millions
of years after their host plants. Journal of Evolutionary Biology
19:1314–1326.
Maddison WP & Maddison DR (2010) Mesquite: a modular
system for evolutionary analysis. Version 2.74. Available at:
mesquiteproject. org/mesquite/download/download.html
Malaise R (1920) Beitrage zur kenntnis schwedischer
blattwespen. Entomologisk Tidskrift 40:97–128.
Malm T & Nyman T (2014) Phylogeny of the symphytan grade
of Hymenoptera: new pieces into the old jigsaw(fly) puzzle.
Cladistics, in press.
Mardulyn P, Othmezouri N, Mikhailov YE & Pasteels JM (2011)
Conflicting mitochondrial and nuclear phylogeographic
signals and evolution of host-plant shifts in the boreomontane leaf beetle Chrysomela lapponica. Molecular
Phylogenetics and Evolution 61:686–696.
Marshall DC, Hill KB, Cooley JR & Simon C (2011)
Hybridization, mitochondrial DNA phylogeography, and
prediction of the early stages of reproductive isolation:
lessons from New Zealand cicadas (genus Kikihia). Systematic
Biology 60:482–502.
53
Mayhew PJ (2007) Why are there so many insect species?
Perspectives from fossils and phylogenies. Biological Reviews
82:425–454.
McCall PJ, Turlings TC, Lewis WJ & Tumlinson JH (1993) Role
of plant volatiles in host location by the specialist parasitoid
Microplitis croceipes Cresson (Braconidae: Hymenoptera).
Journal of Insect Behavior 6:625–639.
McCune B & Mefford MJ (2006) PC-ORD. Multivariate analysis
of ecological data. Version 5. MjM Software Design,
Gleneden Beach, Oregon, USA.
McKenna DD, Sequeira AS, Marvaldi AE & Farrell BD (2009)
Temporal lags and overlap in the diversification of weevils
and flowering plants. Proceedings of the National Academy of
Sciences of the USA 106:7083–7088.
McPeek M & Brown J (2007) Clade age and not diversification
rate explains species richness among animal taxa. American
Naturalist 169:E97–E106.
Meyer J (1987) Plant Galls and Gall Inducers. Gebrüder
Borntraeger, Berlin.
Miller MA, Pfeiffer W, Schwartz T (2010) Creating the CIPRES
Science Gateway for inference of large phylogenetic trees. In:
Proceedings of the Gateway Computing Environments Workshop
(GCE). 14 Nov 2010, New Orleans, LA.
Mitter C, Farrell B & Wiegmann B (1988) The phylogenetic study
of adaptive zones: has phytophagy promoted insect
diversification? American Naturalist 132:107–128.
Morris RJ, Lewis OT & Godfray HC (2004) Experimental
evidence for apparent competition in a tropical forest food
web. Nature 428:310–313.
Murphy SM (2004) Enemy-free space maintains swallowtail
butterfly host shift Proceedings of the National Academy of
Sciences of the USA 101:18048–18052.
Nixon KC (1999) The parsimony ratchet, a new method for
rapid parsimony analysis. Cladistics 15:407–414.
Nosil P & Mooers AO (2005) Testing hypotheses about
ecological specialization using phylogenetic trees. Evolution
59:2256–2263.
54
Nosil P & Crespi BJ (2006) Experimental evidence that predation
promotes divergence in adaptive radiation. Proceedings of the
National Academy of Sciences of the USA 103:9090–9095.
Novotny V, Basset Y, Miller SE, Weiblen GD, Bremer B, Cizek L
& Drozd P (2002) Low host specificity of herbivorous insects
in a tropical forest. Nature 416:841–844.
Novotny V, Drozd P, Miller SE, Kulfan M, Janda M, Basset Y &
Weiblen GD (2006) Why are there so many species of
herbivorous insects in tropical rainforests? Science 313:1115–
1118.
Novotny V, Miller SE, Baje L, Balagawi S, Basset Y, Cizek L,
Craft KJ, Dem F, Drew RA, Hulcr J, Leps J, Lewis OT, Pokon
R, Stewart AJ, Samuelson GA & Weiblen GD (2010) Guildspecific patterns of species richness and host specialization in
plant-herbivore food webs from a tropical forest. Journal of
Animal Ecology 79:1193–1203.
Noyes JS (2013) Universal Chalcidoidea Database. World Wide
Web
electronic
publication,
Available
at
http://www.nhm.ac.uk/research-curation/research/
projects/chalcidoids/.
Nyman T (2000) Phylogeny and Ecological Evolution of GallInducing Sawflies (Hymenoptera: Tenthredinidae). Ph.D. Thesis,
University of Joensuu, Finland.
Nyman T (2002) The willow bud galler Euura mucronata Hartig
(Hymenoptera: Tenthredinidae): one polyphage or many
monophages? Heredity 88:288–295.
Nyman T (2010) To speciate, or not to speciate? Resource
heterogeneity, the subjectivity of similarity, and the
macroevolutionary consequences of niche-width shifts in
plant-feeding insects. Biological Reviews 85:393–411.
Nyman T, Widmer A & Roininen H (2000) Evolution of gall
morphology and host-plant relationships in willow-feeding
sawflies (Hymenoptera: Tenthredinidae). Evolution 54:526–
533.
Nyman T, Farrell BD, Zinovjev AG & Vikberg V (2006a) Larval
habits, host-plant associations, and speciation in nematine
55
sawflies (Hymenoptera: Tenthredinidae). Evolution 60:1622–
1637.
Nyman T, Zinovjev A, Vikberg V & Farrell B (2006b) Molecular
phylogeny
of
the
sawfly
subfamily
Nematinae
(Hymenoptera: Tenthredinidae). Systematic Entomology
31:569–583.
Nyman T, Bokma F & Kopelke JP (2007) Reciprocal
diversification in a complex plant-herbivore-parasitoid food
web. BMC Biology 5:49.
Nyman T, Vikberg V, Smith DR & Boevé JL (2010) How
common is ecological speciation in plant-feeding insects? A
'Higher' Nematinae perspective. BMC Evolutionary Biology
10:266.
Ohshima I, Tanikawa-Dodo Y, Saigusa T, Nishiyama T, Kitani
M, Hasebe M & Mohri H (2010) Phylogeny, biogeography,
and host-plant association in the subfamily Apaturinae
(Insecta: Lepidoptera: Nymphalidae) inferred from eight
nuclear and seven mitochondrial genes. Molecular
Phylogenetics and Evolution 57:1026–1036.
Peccoud J, Ollivier A, Plantegenest M & Simon J-C (2009) A
continuum of genetic divergence from sympatric host races
to species in the pea aphid complex. Proceedings of the National
Academy of Sciences of the USA 106:7495–7500.
Percy DM, Page RDM & Cronk QCB (2004) Plant-insect
interactions: double-dating associated insect and plant
lineages reveals asynchronous radiations. Systematic Biology
53:120–127.
Pitz KM, Dowling AP, Sharanowski BJ, Boring CA, Seltmann
KC & Sharkey MJ (2007) Phylogenetic relationships among
the Braconidae (Hymenoptera: Ichneumonoidea): a
reassessment of Shi et al. (2005). Molecular Phylogenetics and
Evolution 43:338–343.
Posada D (2008) jModelTest: phylogenetic model averaging.
Molecular Biology and Evolution 25:1253–1256.
Powell W, Pennacchio F, Poppy GM & Tremblay E (1998)
Strategies involved in the location of hosts by the parasitoid
56
Aphidius
ervi
Haliday
(Hymenoptera:
Braconidae:
Aphidiinae). Biological Control 11:104–112.
Powell TH, Hood GR, Murphy MO, Heilveil JS, Berlocher SH,
Nosil P & Feder JL (2013) Genetic divergence along the
speciation continuum: the transition from host race to species
in Rhagoletis (Diptera: Tephritidae). Evolution 67:2561–76.
Price PW (2005) Adaptive radiation of gall-inducing insects.
Basic and Applied Ecology 6:413–421.
Price PW & Clancy KM (1986) Interactions among three trophic
levels: gall size and parasitoid attack. Ecology 1593–1600.
Price PW & Pschorn-Walcher H (1988) Are galling insects better
protected against parasitoids than exposed feeders? A test
using tenthredinid sawflies. Ecological Entomology 13:195–205.
Price PW & Roininen H (1993) Adaptive radiation in gall
induction. In Wagner M, and Raffa KF (eds). Sawfly Life
History Adaptations to Woody Plants. Academic Press, New
York, pp. 229–257.
Price PW, Fernandes GW & Waring GL (1987) Adaptive nature
of insect galls. Environmental Entomology 16:15–24.
Pschorn-Walcher H & Altenhofer E (1989) The parasitoid
community of leaf-mining sawflies (Fenusini and
Heterarthrini): a comparative analysis. Zoologisher Anzeiger
222:37–56.
Quicke DLJ, Laurenne NM, Fitton MG & Broad GR (2009) A
thousad and one wasps: a 28S rDNA and morphological
phylogeny of the Ichneumonidae (Insecta: Hymenoptera)
with an investigation into aligment parameter space and
elision. Journal of Natural History 43:1305–1421.
Richter A & Kasparyan R (2013) Tachinid (Diptera, Tachinidae)
parasitoids
of
sawflies
(Hymenoptera,
Symphyta).
Entomological Review 93:630–633.
Roderick GK (1997) Herbivorous insects and the Hawaiian
silversword alliance: coevolution or cospeciation? Pacific
Science 51:440–449.
Roininen H & Danell K (1997) Mortality factors and resource use
of the bud-galling sawfly, Euura mucronata (Hartig), on
willows (Salix spp.) in arctic Eurasia. Polar Biology 18:325–330.
57
Roininen H, Danell K, Zinovjev A, Vikberg V & Virtanen R
(2002) Community structure, survival and mortality factors
in arctic populations of Eupontania leaf gallers. Polar Biology
25:605–611.
Roininen H, Nyman T & Zinovjev A (2005) Biology, ecology,
and evolution of gall-inducing sawflies (Hymenoptera:
Tenthredinidae and Xyelidae). In Raman A, Schaefer CW,
and Withers TM (eds). Biology, Ecology and Evolution of Gallinducing Arthropods, Volumes 1 and 2. Science Publishers, Inc.,
pp. 467–494.
Ronquist F & Huelsenbeck JP (2003) MrBayes 3: Bayesian
phylogenetic inference under mixed models. Bioinformatics
19:1572–1574.
Ronquist F, Teslenko M, van der Mark P, Ayres DL, Darling A,
Höhna S, Larget B, Liu L, Suchard MA & Huelsenbeck JP
(2012) MrBayes 3.2: efficient Bayesian phylogenetic inference
and model choice across a large model space. Systematic
Biology 61:539–542.
Rosenblum EB & Harmon LJ (2011) "Same same but different":
Replicated ecological speciation at white sands. Evolution
65:946–960.
Rott AS & Godfray HCJ (2000) The structure of a leafminer–
parasitoid community. Journal of Animal Ecology 69:274–289.
Rundle HD & Nosil P (2005) Ecological speciation. Ecology
Letters 8:336–352.
Salvo A & Valladares GR (2004) Looks are important: parasitic
assemblages of agromyzid leafminers (Diptera) in relation to
mine shape and contrast. Journal of Animal Ecology 73:494–505.
Scheffer SJ & Hawthorne DJ (2007) Molecular evidence of hostassociated genetic divergence in the holly leafminer
Phytomyza glabricola (Diptera: Agromyzidae): apparent
discordance among marker systems. Molecular Ecology
16:2627–2637.
Scheffer SJ, Winkler IS & Wiegmann BM (2007) Phylogenetic
relationships within the leaf-mining flies (Diptera:
Agromyzidae) inferred from sequence data from multiple
genes. Molecular Phylogenetics and Evolution 42:756–775.
58
Schluter D (2001) Ecology and the origin of species. Trends in
Ecology & Evolution 16:372–380.
Schluter D & Conte GL (2009) Genetics and ecological
speciation. Proceedings of the National Academy of Sciences of the
USA 106:9955–9962.
Segar ST, Lopez-Vaamonde C, Rasplus JY & Cook JM (2012) The
global
phylogeny
of
the
subfamily
Sycoryctinae
(Pteromalidae): parasites of an obligate mutualism. Molecular
Phylogenetics and Evolution 65:116–125.
Sikes DS & Lewis PO (2001) PAUPRat: a tool to implement
parsimony ratchet searches using PAUP*. Available at:
http://viceroy. eeb. uconn. edu/paupratweb/pauprat. htm.
Simmons, MP & Ochoterena H (2000) Gaps as characters in
sequence-based phylogenetic analysis. Systematic Biology
49:369–381.
Sinclair RJ & Hughes L (2010) Leaf miners: the hidden
herbivores. Austral Ecology 35:300–313.
Singer MS & Stireman JO (2005) The tri-trophic niche concept
and adaptive radiation of phytophagous insects. Ecology
Letters 8:1247–1255.
Skvortsov AK (1999) Willows of Russia and Adjacent Countries.
University of Joensuu, Joensuu.
Slove J & Janz N (2011) The relationship between diet breadth
and geographic range size in the butterfly subfamily
Nymphalinae – a study of global scale. PLoS ONE 6:e16057.
Smith DR (1971) Nearctic sawflies. III. Heterarthrinae: adults
and larvae (Hymenotera: Tenthredinidae). Uniteds States
Department of Agriculture Technical Bulletin No. 1420 p. 84.
Smith DR (1979) Suborder Symphyta. In Krombein KV, Hurd
PD, Smith DR, and Burks BD (eds). Catalog of Hymenoptera in
America North of Mexico. Smithsonian Institution Press,
Washington, DC, pp. 3–137.
Smith EL (1970) Biosystematics and morphology of Symphyta.
II. Biology of gall-making nematine sawflies in the California
region. Annals of the Entomological Society of America 63:36–51.
Smith MA, Woodley NE, Janzen DH, Hallwachs W & Hebert PD
(2006) DNA barcodes reveal cryptic host-specificity within
59
the presumed polyphagous members of a genus of parasitoid
flies (Diptera: Tachinidae). Proceedings of the National Academy
of Sciences of the USA 103:3657–3662.
Smith MA, Wood DM, Janzen DH, Hallwachs W & Hebert PDN
(2007) DNA barcodes affirm that 16 species of apparently
generalist tropical parasitoid flies (Diptera, Tachinidae) are
not all generalists. Proceedings of the National Academy of
Sciences of the USA 104:4967–4972.
Smith MA, Rodriguez JJ, Whitfield JB, Deans AR, Janzen DH,
Hallwachs W & Hebert PD (2008) Extreme diversity of
tropical parasitoid wasps exposed by iterative integration of
natural history, DNA barcoding, morphology, and
collections. Proceedings of the National Academy of Sciences of the
USA 105:12359–12364.
Smith MA, Eveleigh ES, McCann KS, Merilo MT, McCarthy PC
& Van Rooyen KI (2011) Barcoding a quantified food web:
crypsis, concepts, ecology and hypotheses. PLoS ONE
6:e14424.
Stamatakis A, Hoover P & Rougemont J (2008) A rapid
bootstrap algorithm for the RAxML Web servers. Systematic
Biology 57:758–771.
Stireman JO (2005) The evolution of generalization? Parasitoid
flies and the perils of inferring host range evolution from
phylogenies. Journal of Evolutionary Biology 18:325–336.
Stireman JO, Nason JD & Heard SB (2005) Host-associated
genetic differentiation in phytophagous insects: general
phenomenon or isolated exceptions? Evidence from a
goldenrod-insect community. Evolution 59:2573–2587.
Stireman JO, Nason JD, Heard SB & Seehawer JM (2006)
Cascading host-associated genetic differentiation in
parasitoids of phytophagous insects. Proceedings of the Royal
Society B: Biological Sciences 273:523–530.
Stireman JO, Devlin H, Carr TG & Abbot P (2010) Evolutionary
diversification of the gall midge genus Asteromyia
(Cecidomyiidae) in a multitrophic ecological context.
Molecular Phylogenetics and Evolution 54:194–210.
60
Stireman JO, Devlin H & Abbot P (2012) Rampant host- and
defensive phenotype-associated diversification in a
goldenrod gall midge. Journal of Evolutionary Biology 25:1991–
2004.
Stone GN & Schönrogge K (2003) The adaptive significance of
insect gall morphology. Trends in Ecology & Evolution 18:512–
522.
Strong DR, Lawton JH & Southwood TRE (1984) Insects on
Plants: Community Patterns and Mechanisms. Harvard Univ.
Press, Cambridge, MA.
Swofford DL (2003) PAUP*. Phylogenetic Analysis Using
Parsimony (*and Other Methods). Version 4. Sinauer
Associates, Sunderland, MA.
Taeger A & Altenhofer E (1998) Kommentare zur Biologie,
Verbreitung
und
Gefahrdung
der
Pflanzenwespen
Deutschlands (Hymenoptera, Symphyta). In Blank S M &
Taeger A (eds.) Pflanzenwespen Deutschlands (Hymenoptera.
Symphyta). Kommentierte Bestandsaufnahme. Goecke &
Evers, Keltern. pp. 49–135
Taeger A, Blank SM & Liston AD (2010) World catalog of
Symphyta (Hymenoptera). Zootaxa 2580:1–1064.
Tamura K, Peterson D, Peterson N, Stecher G, Nei M & Kumar S
(2011) MEGA5: molecular evolutionary genetics analysis
using maximum likelihood, evolutionary distance, and
maximum parsimony methods. Molecular Biology and
Evolution 28:2731–2739.
Tilmon KJ, Danforth BN, Day WH & Hoffmann MP (2000)
Determining parasitoid species composition in a host
population: a molecular approach. Annals of the Entomological
Society of America 93:640–647.
Via S, Bouck AC & Skillman S (2000) Reproductive isolation
between divergent races of pea aphids on two hosts. II.
Selection against migrants and hybrids in the parental
environments. Evolution 54:1626–1637.
Viitasaari M (2002) A review of the extant families of the
Hymenoptera. In Viitasaari M (Ed) Sawflies I. Tremex Press,
Jyväskylä, pp. 175–182.
61
Whitfield JB & Kjer KM (2008) Ancient rapid radiations of
insects: challenges for phylogenetic analysis. Annual Reviews
of Entomology 53:449–472.
Wilson JS, Forister ML, Dyer LA, O'Connor JM, Burls K,
Feldman CR, Jaramillo MA, Miller JS, Rodríguez-Castañeda
G, Tepe EJ, Whitfield JB & Young B (2012) Host conservatism,
host shifts and diversification across three trophic levels in
two Neotropical forests. Journal of Evolutionary Biology 25:532–
546.
Winkler IS & Mitter C (2008) The phylogenetic dimension of
insect-plant interactions: a review of recent evidence. In
Tilmon K J (Ed) Specialization, Speciation, and Radiation: the
Evolutionary Biology of Herbivorous Insects. University of
California Press, Berkeley, CA. pp. 240–263.
Wirta HK, Hebert PD, Kaartinen R, Prosser SW, Várkonyi G &
Roslin T (2014) Complementary molecular information
changes our perception of food web structure. Proceedings of
the National Academy of Sciences of the USA Early edition,
www.pnas.org/cgi/doi/10.1073/pnas.1316990111.
Yao H, Song J, Liu C, Luo K, Han J, Li Y, Pang X, Xu H, Zhu Y,
Xiao P & Chen S (2010) Use of ITS2 region as the universal
DNA barcode for plants and animals. PLoS ONE 5:e13102.
Zaldivar-Riverón A, Mori M & Quicke DL (2006) Systematics of
the cyclostome subfamilies of braconid parasitic wasps
(Hymenoptera: Ichneumonoidea): a simultaneous molecular
and
morphological
Bayesian
approach.
Molecular
Phylogenetics and Evolution 38:130–145.
Zaldívar-Riverón A, Shaw MR, Sáez AG, Mori M, Belokoblylskij
SA, Shaw SR & Quicke DL (2008) Evolution of the parasitic
wasp subfamily Rogadinae (Braconidae): phylogeny and
evolution of lepidopteran host ranges and mummy
characteristics. BMC Evolutionary Biology 8:329.
Ødegaard F, Diserud OH & Østbye K (2005) The importance of
plant relatedness for host utilization among phytophagous
insects. Ecology Letters 8:612–617.
62
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dissertations | 154 | Sanna Leppänen | Effect of host-plant use on speciation and parasitoid community structure in internal-feeding sawflies
Sanna Leppänen
Effect of host-plant use on
speciation and parasitoid
community structure in
internal-feeding sawflies
Sanna Leppänen
Effect of host-plant use on
speciation and parasitoid
community structure in
internal-feeding sawflies
Publications of the University of Eastern Finland
Dissertations in Forestry and Natural Sciences