ary
niversity of
gen,
ion when we
thin a single
ormal terms
upercolony.’’
nt, infamous
m having its
pped. As the
her supercoffett’s review
es on social
de, this field
dings due to
myself). Mofy conflicting
ading to the
ntine ants in
eties that are
dentity’’ that
ffett, this is-
n qualify for
offett in that
c, it concerns
organization.
is not a conving the life-
extensive
society
of one
of the invasive
species. Normaldue
terms
of research
has been
hampered
by misunderstandings
to
do
not fit anymore:
thisviews
is not(including
just a colony,
but aof‘‘supercolony.’’
diverging
or changed
those
myself). MofThe
iconic
supercolonial
species
is the of
Argentine
ant,conflicting
infamous
fett now
makes
sense of the
complex
seemingly
as
a pestand
andtracks
now very
well studied, all
way from
having
its
studies
the development
of the
insights
leading
to the
genome consensus
sequenced(Helanterä
to its global
mapped. ants
As the
current
et distribution
al. 2009): Argentine
in
Argentine
ant canand
be introduced
the key to understanding
other supercoboth their native
ranges form societies
that are
lonial
and/or
invasiveinherit
ants, it their
is veryodor
timely
that Moffett’s
review
mutually
aggressive,
profile
‘‘identity’’
that
Commentaries
on Invited Review
(2012)
focuses
on
how
we
interpret
recent
studies
on
social
determines who they consider friend or foe (Moffett, this
isorganization
this species.
more than
a decade, this field
sue) and can in
potentially
be For
of unlimited
size.
of Does
research
has been
hampered
by misunderstandings
duefor
to
the type
of society
of the Argentine
ant then qualify
diverging
changed
views (including
those
ofMoffett
myself).inMofthe specialor
term
‘‘supercolony’’?
I fully agree
with
that
fett
now makesofsense
of the complex
of seemingly
conflicting
the discussion
supercolonies
is not only
semantic, it
concerns
studies
tracks
development
of of
insights
to the
whetherand
they
are the
a distinct
category
socialleading
organization.
current
consensus
(Helanterä
et
al.
2009):
Argentine
in
Here, it is important to realize that a supercolony is notants
a conboth
their
native
and
introduced
ranges
form
societies
that
are
sequence of size; rather, large size is a result of having the lifemutually
aggressive,
inherit their
odor profile
that
style typical
of a supercolony.
Therefore,
I have‘‘identity’’
to differ with
determines
who
they
consider
friend
or
foe
(Moffett,
this
isMoffett about his proposed definition, where an exact colony
sue)
andmillion
can potentially
be of unlimited
size—1
individuals—is
the tippingsize.
point from colony
the type Ant
of society
of the
then qualify
for
to Does
supercolony.
societies
withArgentine
divergentant
structures
and life
the
specialmay
termreach
‘‘supercolony’’?
I fully
agree
with
Moffett in that
histories
this number
(e.g.,
Atta
leaf-cutters
and
the
discussion
of supercolonies
is not
semantic,
it concerns
Dorylus
army ants),
and nothing
of only
biological
relevance
hapwhether
they
a distinct
pens when
thisare
arbitrary
limitcategory
is passed.of social organization.
Here,
it
is
important
to
realize
that
a
supercolony
is
not
a
conThat leaves 4 other life-history characteristics being shared
sequence
of
size;
rather,
large
size
is
a
result
of
having
the
lifeamong supercolonial ants. These characteristics are not trivial
style
typical
a supercolony.
Therefore,
I have
to differ
and seem
to of
form
the supercolonial
paradigm
against
whichwith
fuMoffett
about
hisbeproposed
ture studies
will
held up. definition, where an exact colony
size—1
million individuals—is
the tipping
point
from colony
1. A common
origin within sites.
The entire
supercolony
at
to supercolony.
Ant
societies
with
divergent
structures
and life
a given site is derived from a single founding group
of
histories
may reach
number
(e.g., Atta
and
individuals,
thatthis
is, it
is continuous
overleaf-cutters
time. AlternaDorylus army ants), and nothing of biological relevance haptively, the supercolony could have developed from the
pens when this arbitrary limit is passed.
fusion of neighboring independent colonies, but no
That leaves 4 other life-history characteristics being shared
such cases are known (Helanterä et al. 2009).
among supercolonial ants. These characteristics are not trivial
2. Identity by descent across sites. The founding group of
and seem to form the supercolonial paradigm against which fuindividuals at a given site is a small fraction of the same
ture studies will be held up.
supercolony
residing
at asites.
different
site (the
source) and
1. A
common origin
within
The entire
supercolony
at
continues
to
keep
that
same
colony’s
‘‘identity’’
a given site is derived from a single founding (Moffett,
group of
this issue) despite
separation,
sometimes
even
individuals,
that is,physical
it is continuous
over
time. Alternaat
a
continental
scale
(Van
Wilgenburg
et
al.
2010).
In
tively, the supercolony could have developed from the
principle,
single inseminated
queencolonies,
could indepenfusion
of aneighboring
independent
but no
dentlycases
haveare
founded
supercolony
at 2009).
a new site, likely
such
knownthe
(Helanterä
et al.
Behavioral Ecology
breakingby
the
sharedacross
colonysites.
identity
sites,group
but this
2. Identity
descent
Theacross
founding
of
is
not
what
we
see.
individuals at a given site is a small fraction of the same
The supercolony
Author 2012. Published
by at
Oxford
Universitysite
Press
on behalf
of and
residing
a different
(the
source)
2 International Society for Behavioral Ecology. All rights reserved.
the
continues
to
keep
that
same
colony’s
‘‘identity’’
(Moffett,
For permissions, please e-mail: [email protected]
this issue) despite physical separation, sometimes even
at a continental scale (Van Wilgenburg et al. 2010). In
Moffett
MW. 2012.aSupercolonies
of billionsqueen
in an invasive
what is
principle,
single inseminated
could ant:
indepena society?
23. the supercolony at a new site, likely
dentlyBehav
have Ecol.
founded
Schmidt
AM, D’Ettorre
P, Pedersen
2010. Low
levels
of nestmate
breaking
the shared
colonyJS.
identity
across
sites,
but this
discrimination despite high genetic differentiation in the invasive
is
not
what
we
see.
pharaoh ant. Front Zool. 7:20.
3. A continuous network of nests. At a given site, the
The Author 2012. Published by Oxford University Press on behalf of
supercolony
by budding,
forming
a network
the International
Societyexpands
for Behavioral
Ecology. All rights
reserved.
For permissions,
please e-mail: [email protected]
of interconnected
nests, and these connections may
persist keeping the supercolony genetically homogeneous. Colony budding is important in many polygynous ant species but usually leads to population
viscosity and the formation of socially independent
daughter colonies by breaking-up the social network
(Debout et al. 2007).
4. Self-contained reproduction. The supercolony reproduces by virgin queens mating exclusively with males
reared in the same supercolony (Vogel et al. 2009) or
has become clonal so that sex is no longer required
(Fournier et al. 2005). The closed breeding unit that
results is unlike the dispersal of sexuals and outbreeding
found in most other social insects.
Time will tell whether these differences—more remarkable
than colony size alone—will hold true, but if they do, they may
define supercoloniality as a distinct form of social organization that requires a major transition in evolution (McShea
and Changizi 2003; Bourke 2011). Recent studies do indeed
suggest a potential for supercolonial lineage selection, not
only in the Argentine ant (Vogel et al. 2009) but also in the
little fire ant (Foucaud et al. 2010) and the pharaoh ant
(Schmidt et al. 2010). After all, these colonies may not only
be super sized but also transitioning to ‘‘hypersocial,’’ trapped in closed societies each with its own evolutionary fate.
Key words: kin selection, levels of selection, Linepithema humile,
supercolony, unicoloniality.
Address correspondence to J.S. Pedersen. E-mail: [email protected].
define supercoloniality as a distinct form of social organizaces by virgin queens mating exclusively with males
tion that requires a major transition in evolution (McShea
reared in the same supercolony (Vogel et al. 2009) or
and Changizi 2003; Bourke 2011). Recent studies do indeed
hasa become
so that sex islineage
no longer
required
suggest
potentialclonal
for supercolonial
selection,
not
(Fournier
et al. 2005).
The etclosed
breeding
unitin that
only in
the Argentine
ant (Vogel
al. 2009)
but also
the
is unlike
the dispersal
of sexuals
andpharaoh
outbreeding
little results
fire ant
(Foucaud
et al. 2010)
and the
ant
found
other
social
(Schmidt
etin
al.most
2010).
After
all,insects.
these colonies may not only
935
tell but
whether
differences—more
remarkable
beTime
superwill
sized
also these
transitioning
to ‘‘hypersocial,’’
trapthan
colony
size
alone—will
hold
true,
but
if
they
do,
they
may
ped in closed societies each with its own evolutionary fate.
define supercoloniality as a distinct form of social organizationwords:
that requires
a major
transition
in evolution
(McShea
Key
kin selection,
levels
of selection,
Linepithema
humile,
and Changiziunicoloniality.
2003; Bourke 2011). Recent studies do indeed
supercolony,
suggest a potential for supercolonial lineage selection, not
only in the Argentine ant (Vogel et al. 2009) but also in the
Address correspondence to J.S. Pedersen. E-mail: [email protected].
little fire ant (Foucaud et al. 2010) and the pharaoh ant
(Schmidt et al. 2010). After all, these colonies may not only
be super30
sized
but also
transitioning
‘‘hypersocial,’’
trapReceived
November
2011;
revised 14 to
February
2012; accepted
pedFebruary
in closed
societies each with its own evolutionary fate.
26
2012.
Key
kin selection, levels of selection, Linepithema humile,
doi: words:
10.1093/beheco/ars047
supercolony, unicoloniality.
FUNDING
Address correspondence to J.S. Pedersen. E-mail: [email protected].
Danish National Research Foundation (to J.S.P.).
Received 30 November 2011; revised 14 February 2012; accepted
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a society?
23.
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Keller AM,
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Carillo J, Queller DC. 2009. Unicolonial
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Invited Commentary
Comment on Moffett: ‘‘Supercolonies of
billions in an invasive ant: What is a society?’’
Philip J. Lester and Monica A. M. Gruber
Centre for Biodiversity and Restoration Ecology, Victoria University
of Wellington, PO Box 600, Wellington, New Zealand
The term ‘‘supercolony’’ was first used by Gris and Cherix (1977)
and has since been used often to describe ants that form expansive colonies. Yet, Moffett (2012) demonstrates that there are
a variety of interpretations of supercolony and a diversity of hypotheses exist about how supercolonies have arisen in Argentine
ants. His article will provoke further debate. There are 2 major
themes to Moffett (2012) on which we would like to comment
and highlight for future research. The first is how we should
define an Argentine ant supercolony. The second theme is why
such supercolonies grow so large in their invaded ranges.
What should we consider to be a supercolony for Argentine
ants? Moffett (2012) suggests an Argentine ant supercolony
would be a polydomous colony of at least 1 million individuals.
This lower threshold criterion of 1 million individuals would in
practice often be hard to satisfy given the difficulty of counting
ants. Previously, ant supercolonies have been defined as very
large entities, comprising of many queens, integrated harmoniously across an area encompassing several square meters to
many square kilometers, with individual ants freely, but not
necessarily evenly, mixing across spatially separated parts of its
domain (Bourke and Franks 1995; Crozier and Pamilo 1996;
Steiner et al. 2010). Using either this or the Moffett (2012)
Van Wilgenbur
sion of a sing
Vogel V, Peder
netic structu
Evolution. 63
benefits (i.e., fi
and the invad
The key eco
onies in their
range, the ma
been estimate
(Heller 2004)
as many order
Wilgenburg e
others (Peder
colonies in th
the dictates o
nies become s
clearly differe
genetic chan
during introd
Much of the w
tively neutral
under selectio
ant genome a
polymorphism
allow us to id
growth. It is a
responsible fo
range, they ar
man disturban
et al. 2011), a
role in increa
Moffett (20
further invest
ing of invasiv
ary
es of
society?’’
ria University
Cherix (1977)
t form expanhat there are
diversity of hyn in Argentine
e are 2 major
e to comment
ow we should
theme is why
ranges.
for Argentine
supercolony
n individuals.
uals would in
y of counting
fined as very
ated harmonire meters to
eely, but not
ed parts of its
Pamilo 1996;
Moffett (2012)
onies in their
04; Pedersen
colony’’ (van
ony? We agree
unlikely to be
etches on for
functional. To
themes to Moffett (2012) on which we would like to comment
ants. Previously, ant supercolonies have been defined as very
and highlight for future research. The first is how we should
large entities, comprising of many queens, integrated harmonidefine an Argentine ant supercolony. The second theme is why
ously across an area encompassing several square meters to
such supercolonies grow so large in their invaded ranges.
many square kilometers, with individual ants freely, but not
What should we consider to be a supercolony for Argentine
necessarily evenly, mixing across spatially separated parts of its
ants? Moffett (2012) suggests an Argentine ant supercolony
domain (Bourke and Franks 1995; Crozier and Pamilo 1996;
would be a polydomous colony of at least 1 million individuals.
Steiner et al. 2010). Using either this or the Moffett (2012)
936
This lower threshold criterion of 1 million individuals would in
definition, Argentine ants clearly form supercolonies in their
practice often be hard to satisfy given the difficulty of counting
native range (Tsutsui and Case 2001; Heller 2004; Pedersen
ants. Previously, ant supercolonies have been defined as very
et al. 2006).
large entities, comprising of many queens, integrated harmoniShould we really consider the ‘‘global supercolony’’ (van
ously across an area encompassing several square meters to
Wilgenburg et al. 2010) to be a functional supercolony? We agree
many square kilometers, with individual ants freely, but not
with Gordon (2010) who proposes that there is unlikely to be
necessarily evenly, mixing across spatially separated parts of its
functional supercolony of Argentine ants that stretches on for
domain (Bourke and Franks 1995; Crozier and Pamilo 1996;
many kilometers. The key word in this sentence is functional. To
Steiner et al. 2010). Using either this or the Moffett (2012)
us, the key benefit of a functional supercolony is the long-term
definition, Argentine ants clearly form supercolonies in their
persistence of a specific local genetic lineage or nest clusters
native range (Tsutsui and Case 2001; Heller 2004; Pedersen
(sensu Heller et al. 2006) within the supercolony. Under a
et al. 2006).
Darwinian framework, supercolonies likely evolved in their native
Should we really consider the ‘‘global supercolony’’ (van
range as a result of benefits for the ant’s fitness, as an extension
Wilgenburg et al. 2010) to be a functional supercolony? We agree
of existing kin-selected behavior (Helanterä et al. 2009). In New
with Gordon (2010) who proposes that there is unlikely to be
Zealand, Argentine ants form a single supercolony (Corin et al.
functional supercolony of Argentine ants that stretches on for
2007) and have been considered part of the main global supermany kilometers. The key word in this sentence is functional. To
colony (van Wilgenburg et al. 2010). Populations form disconus, the key benefit of a functional supercolony is the long-term
tinuous distributions even within cities, and isolated nest clusters
persistence of a specific local genetic lineage or nest clusters
occasionally collapse (Cooling et al. 2011). Thus, even individual
(sensu Heller et al. 2006) within the supercolony. Under a
New Zealand cities typically do not have single supercolonies with
Darwinian framework, supercolonies likely evolved in their native
all their functional benefits. Rather, the supercolony is effectively
range as a result of benefits for the ant’s fitness, as an extension
a mosaic of nest clusters within the supercolony or ‘‘metacoloof existing kin-selected behavior (Helanterä et al. 2009). In New
nies’’ (sensu Heller et al. 2008) dynamically forming and dissolvZealand, Argentine ants form a single supercolony (Corin et al.
ing over varying timescales (Cooling et al. 2011). We suspect that
2007) and have been considered part of the main global superArgentine ant supercolonies form similar discontinuous distribucolony (van Wilgenburg et al. 2010). Populations form discontions throughout their natural and invaded range, as suggested
tinuous distributions even within cities, and isolated nest clusters
by Heller et al. (2008). However, as Moffett (2012) suggests,
occasionally collapse (Cooling et al. 2011). Thus, even individual
further research is needed on their long-termBehavioral
distribution
patEcology
New Zealand cities typically do not have single supercolonies
with
terns, worker exchange, and persistence. We suggest that a key
all their functional benefits. Rather, the supercolony is effectively
aspect of this future research be on the long-term functional
a mosaic of nest clusters within the supercolony or ‘‘metacolonies’’
Heller
et al. 2008)
dynamically
forming
and of
dissolv The (sensu
Author 2012.
Published
by Oxford
University Press
on behalf
the International
Society
for Behavioral
Ecology.
rights reserved.
ing
over varying
timescales
(Cooling
et al.All2011).
We suspect that
For permissions, please e-mail: [email protected]
Argentine ant supercolonies form similar discontinuous distributions throughout their natural and invaded range, as suggested
by Heller et al. (2008). However, as Moffett (2012) suggests,
further research is needed on their long-term distribution patterns, worker exchange, and persistence. We suggest that a key
aspect of this future research be on the long-term functional
benefits (i.e., fitness benefits) of supercolonies in both the native
The Author 2012. Published by Oxford University Press on behalf of
and
the invaded
ranges.
the International
Society
for Behavioral Ecology. All rights reserved.
ForThe
permissions,
please e-mail:
[email protected]
key ecological
difference
between Argentine ant supercolonies in their native and invaded range is size. In their native
range, the maximum measured diameter of a supercolony has
been estimated at 1 km, and they are frequently much smaller
(Heller 2004). In the introduced ranges, their size is reported
as many orders of magnitude higher (e.g., Corin et al. 2007; van
Wilgenburg et al. 2010). We agree with Moffett (2012) and
others (Pedersen et al. 2006; Helanterä et al. 2009) that supercolonies in the invaded range are to a large degree ‘‘following
the
2 dictates of the ancestral behavior.’’ But because supercolonies become so much larger in the invaded range, something is
clearly different. As for mechanisms, it is too early to write-off
genetic changes resulting from either genetic bottlenecks
Corin SE,introduction
Abbott KL, Richie
PA, Lesteron
PJ.established
2007. Large populations.
scale unicoloduring
or selection
niality: the population and colony structure of the invasive Argentine
Much
of the work to date on Argentine ants has involved selecant (Linepithema humile) in New Zealand. Insectes Soc. 54:275–282.
tively
neutral molecular markers rather than markers for genes
Crozier RH, Pamilo P. 1996. Evolution of social insect colonies. Sex
under
selection.
Progress in Oxford
both understanding
the Argentine
allocation
and kin-selection.
(UK): Oxford University
Press.
ant
genome
geneticstudies.
techniques
such
single nucleotide
Gordon
DM. and
2010.inColonial
Boston
Rev.as35:59–62.
polymorphism
forgrandes
these colonies
ants (Smith
et al. 2011)
Gris G, Cherix D.markers
1977. Les
de fourmis
des boismay
du
allow
to identify
specific
with supercolony
Jura us(groupe
Formica
rufa).genes
Mitt associated
Schweiz Entomol
Gesell. 50:
growth.
It is also possible that ecological mechanisms might be
249–250.
Helanterä H,for
Strassmann
JE, ant
Carrillo
J, Quellersize.
DC. 2009.
Unicolonial
responsible
Argentine
supercolony
In their
invaded
ants: where
do known,
they come
what are
theyassociated
and wherewith
are they
range,
they are
forfrom,
example,
to be
hugoing?
Trends Ecol
24:341–349.
man
disturbance
andEvol.
a lack
of biotic resistance (Roura-Pascual
Heller
NE. 2004.
introduced
and plays
nativeapopulaet
al. 2011),
andColony
clearly,structure
human in
assisted
dispersal
major
tions
the invasive
humile. Insectes Soc.
role
in of
increasing
theArgentine
range ofant,
theLinepithema
supercolony.
51:378–386.
Moffett (2012) identifies several other issues well worthy of
Heller NE, Ingram KK, Gordon DM. 2008. Nest connectivity and colony
further
investigation
and
which will
our55:397–403.
understandstructure
in unicolonial
Argentine
ants.enhance
Insectes Soc.
ing
of NE,
invasive
ants.NJ,How
is it that
Argentine
Heller
Sanders
Gordon
DM. new
2006.colonies
Linking of
temporal
and
ants
arisescales
in their
range?
work has
spatial
in native
the study
of Recent
an Argentine
antsuggested
invasion. that
Biol
worker
aggression
may play an important role in reproductive
Invasions.
8:501–507.
interference
(Sunamura
al. 2011).
Should
we expect
to see
Liang D, Silverman
J. 2000.et‘‘You
are what
you eat’’:
diet modifies
cuticularspeciation
hydrocarbons
and
nestmate
in the
Argentine
incipient
even
within
theirrecognition
native range?
What
is the
ant, Linepithema
humile.
Naturwissenschaften.
87:412–416.
actual
role of food
in recognition
and aggression
in Argentine
Moffett
MW.
2012.
Supercolonies
of billions
in an invasive
What is
ants?
We
and
others
have managed
to aggression
by ant:
modifying
a society?.
Behav Ecol.
doi: 10.1093/beheco/ars043.
their
diet (Liang
and Silverman
2000; Corin et al. 2007), but
how much natural variation in food consumption influences
responsible for Argentine ant supercolony size. In their invaded
during introduction or selection on established populations.
range, they are known, for example, to be associated with huMuch of the work to date on Argentine ants has involved selecman disturbance and a lack of biotic resistance (Roura-Pascual
tively neutral molecular markers rather than markers for genes
et al. 2011), and clearly, human assisted dispersal plays a major
under selection. Progress in both understanding the Argentine
role in increasing the range of the supercolony.
ant genome and in genetic techniques such as single nucleotide
Moffett (2012) identifies several other issues well worthy of
polymorphism markers for these ants (Smith et al. 2011) may
further investigation and which will enhance our understandallow us to identify specific genes associated Behavioral
with supercolony
Ecology
ing of invasive ants. How is it that new colonies
of Argentine
growth. It is also possible that ecological mechanisms might be
ants arise in their native range? Recent work has suggested that
responsible for Argentine ant supercolony size. In their invaded
worker aggression may play an important role in reproductive
range, they are known, for example, to be associated with huinterference (Sunamura et al. 2011). Should we expect to see
man disturbance and a lack of biotic resistance (Roura-Pascual
incipient speciation even within their native range? What is the
et al. 2011), and clearly, human assisted dispersal plays a major
actual role of food in recognition and aggression in Argentine
role in increasing the range of the supercolony.
ants? We and others have managed to aggression by modifying
Moffett (2012) identifies several other issues well worthy of
their diet (Liang and Silverman 2000; Corin et al. 2007), but
further investigation and which will enhance our understandhow much natural variation in food consumption influences
ing of invasive ants. How is it that new colonies of Argentine
aggression remains to be seen. Clearly, we have much to
ants arise in their native range? Recent work has suggested that
understand regarding these invasive ants.
worker aggression may play an important role in reproductive
interference (Sunamura et al. 2011). Should we expect to see
incipient
even
within
their Linepithema
native range?humile,
What issize,
the
Key
words:speciation
Argentine
ant,
fitness,
actual role of food in recognition and aggression in Argentine
supercolony.
ants? We and others have managed to aggression by modifying
their diet (Liang and Silverman 2000; Corin et al. 2007), but
Address
correspondence
to P.J. Lester.
E-mail:
[email protected].
how much
natural variation
in food
consumption
influences
aggression remains to be seen. Clearly, we have much to
understand
regarding 2011;
these revised
invasive28ants.
Received
28 December
December 2011; accepted
26 February 2012.
Key 10.1093/beheco/ars048
words: Argentine ant, fitness, Linepithema humile, size,
doi:
supercolony.
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Corin SE, Abbott KL, Richie PA, Lester PJ. 2007. Large scale unicoloniality: the population and colony structure of the invasive Argentine
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Liang D, Silverman J. 2000. ‘‘You are what you eat’’: diet modifies
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Behavioral Ecology
ant, Linepithema humile. Naturwissenschaften. 87:412–416.
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Commentaries
InvitedY,Review
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supercolonies of the invasive Argentine ant. Naturwissenschaften.
98:361–368.
Tsutsui ND, Case TJ. 2001. Population genetics and colony structure
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‘‘supercolonies’’:
commentary on Moffett
van Wilgenburg E, Torres CW, Tsutsui ND. 2010. The global expansion of a single ant supercolony. Evol Appl. 3:136–143.
A. V. Suarez and E. L. Suhr
Department of Animal Biology and the Department of Entomology,
School of Integrative Biology, University of Illinois, 505 S. Goodwin
Ave., Urbana, IL 61801, USA
Invited Commentary
Invited Commentary
Ecological and evolutionary perspectives on
Moffett provides a very thorough review of the ‘‘supercolony’’
‘‘supercolonies’’:
a biology
commentary
on Moffett
concept, focusing on the
of the Argentine
ant (Linepithema humile). The term supercolony is being used more and
more
frequently in the social insect literature, however, not
A. V. Suarez and E. L. Suhr
always
to describe
theBiology
same colony
Despite
invoking
Department
of Animal
and the structure.
Department
of Entomology,
an almost
science fiction-like
quality, we
agree with
Moffett
that
School
of Integrative
Biology, University
of Illinois,
505 S.
Goodwin
the
of 61801,
the supercolony
has been valuable, providing
Ave.,concept
Urbana, IL
USA
considerable insight from both an ecological and an evolutionary perspective.
Moffett provides a very thorough review of the ‘‘supercolony’’
Ecologically, the term supercolony is often used to describe
concept, focusing on the biology of the Argentine ant (Linepia polydomous colony that occupies such a large number of nests
thema humile). The term supercolony is being used more and
that it is impossible for all members of the colony to interact in
more frequently in the social insect literature, however, not
their lifetime (Pedersen et al. 2006). That is, the society occualways to describe the same colony structure. Despite invoking
pies many nest sites over such a large area that queens and
an almost science fiction-like quality, we agree with Moffett that
workers who live on one side of the supercolony will never
the concept of the supercolony has been valuable, providing
meet individuals from the other side. As Moffett points out,
considerable insight from both an ecological and an evolutionthis is likely true for many social insects, even those that occupy
ary perspective.
relatively few nest sites over smaller areas. Moffett suggests that
Ecologically, the term supercolony is often used to describe
we restrict the definition of supercolony to societies with at
a polydomous colony that occupies such a large number of nests
least 1 million workers. However, this seems a bit arbitrary;
that it is impossible for all members of the colony to interact in
a number of ant species are known to have more than 1 million
their lifetime (Pedersen et al. 2006). That is, the society occuworkers yet occupy a single nest site. Are these supercolonies in
pies many nest sites over such a large area that queens and
the same sense that a spatially extensive polydomous Argentine
workers who live on one side of the supercolony will never
ant colony is? Species that form supercolonies are also often
meet individuals from the other side. As Moffett points out,
ecologically dominant where they occur, both outcompeting
this is likely true for many social insects, even those that occupy
other species for resources and overwhelming species through
relatively few nest sites over smaller areas. Moffett suggests that
numerical superiority (Holway et al. 2002). However, as
we restrict the definition of supercolony to societies with at
pointed out by Hölldobler and Wilson (1977), research is still
least 1 million workers. However, this seems a bit arbitrary;
needed to determine if ants become ecologically dominant
a number of ant species are known to have more than 1 million
because they form supercolonies or if ecologically dominant
workers yet occupy a single nest site. Are these supercolonies in
ants monopolize resources and subsequently form supercolothe same sense that a spatially extensive polydomous Argentine
nies as a result.
ant colony is? Species that form supercolonies are also often
From an evolutionary perspective, a supercolony can be deecologically dominant where they occur, both outcompeting
fined as the aggregation of ants across many nests that share
other species for resources and overwhelming species through
a common genotype (usually inferred using microsatellites or
numerical superiority (Holway et al. 2002). However, as
mitochondrial DNA) and phenotype (e.g., cuticular hydrocarpointed out by Hölldobler and Wilson (1977), research is still
bon profile). This is likely due to having a shared common anneeded to determine if ants become ecologically dominant
cestry. Subsequently, this approach has been used to examine
because they form supercolonies or if ecologically dominant
the source and introduction history of invasive ants. Recent hoants monopolize resources and subsequently form supercololistic work combining behavior, chemistry, and genetics
nies as a result.
has provided incredible insight into the worldwide spread of
From an evolutionary perspective, a supercolony can be deArgentine ants (Wilgenburg et al. 2010), and supercolony
fined as the aggregation of ants across many nests that share
identity has been used to infer recent exchange of ants bea common genotype (usually inferred using microsatellites or
tween different introduced populations (Tsutsui et al. 2001;
mitochondrial DNA) and phenotype (e.g., cuticular hydrocarCorin et al. 2007; Sunamura et al. 2009; Vogel et al. 2010; Suhr
bon profile). This is likely due to having a shared common anet al. 2011). As Moffett points out, genetic work on both native
cestry. Subsequently, this approach has been used to examine
and introduced populations of Argentine ants suggests little to
the source and introduction history of invasive ants. Recent hoknow gene flow among supercolonies. However, we disagree
listic work combining behavior, chemistry, and genetics
that each supercolony should be considered its own species
has provided incredible insight into the worldwide spread of
(much as each individual is not considered its own species in
Argentine ants (Wilgenburg et al. 2010), and supercolony
identity has been used to infer recent exchange of ants between
different
populations
et al.of 2001;
The Author
2012. introduced
Published by Oxford
University(Tsutsui
Press on behalf
the
International
Society
for Behavioral
Ecology.
rightset
reserved.
Corin
et al. 2007;
Sunamura
et al.
2009;All
Vogel
al. 2010; Suhr
For permissions, please e-mail: [email protected]
et al. 2011). As Moffett points out, genetic work on both native
and introduced populations of Argentine ants suggests little to
know gene flow among supercolonies. However, we disagree
that each supercolony should be considered its own species
(much as each individual is not considered its own species in
The Author 2012. Published by Oxford University Press on behalf of
the International Society for Behavioral Ecology. All rights reserved.
For permissions, please e-mail: [email protected]
937
Behavioral Ecology
clonal organisms). More work is needed to determine the spatial extent of gene flow in species that form supercolonies.
We agree with Moffett that we need to move past semantic arguments when discussing supercolonies. However, we believe that
both ecological and evolutionary examinations of supercolonies
need to be conducted from the perspective of the population.
A population can be defined as a group of colonies that have
the potential to exchange genes or compete for resources. A population can therefore have many colonies, even many supercoloclonal organisms). More work is needed to determine the spanies. However, the term unicolonial, which is often considered
tial extent of gene flow in species that form supercolonies.
synonymous with supercolony (Pedersen et al. 2006), should
We agree with Moffett that we need to move past semantic argube restricted to describe situations in which the entire population
ments when discussing supercolonies. However, we believe that
consists of only one supercolony (a ‘‘unicolonial population’’
both ecological and evolutionary examinations of supercolonies
Hölldobler and Wilson 1977; Suarez et al. 2008).
need to be conducted from the perspective of the population.
Research is still clearly needed on the biology of species that
A population can be defined as a group of colonies that have
form supercolonies as many unanswered questions remain. For
the potential to exchange genes or compete for resources. A popexample, how do supercolonies arise and how long do they last?
ulation can therefore have many colonies, even many supercoloHow much variation in social parameters exists in native popnies. However, the term unicolonial, which is often considered
ulations of species that can form supercolonies (e.g., colony
synonymous with supercolony (Pedersen et al. 2006), should
size, queen number, intra- vs. intercolony genetic diversity, gene
be restricted to describe situations in which the entire population
flow among colonies)? Is there conflict over reproduction
consists of only one supercolony (a ‘‘unicolonial population’’
within supercolonies or are they as harmonious as Moffett
Hölldobler and Wilson 1977; Suarez et al. 2008).
implies? Over what spatial scales are food and information exResearch is still clearly needed on the biology of species that
changed (Heller et al. 2008)? These last 2 questions in particform supercolonies as many unanswered questions remain. For
ular address whether or not supercolonies are effectively made
example, how do supercolonies arise and how long do they last?
up of aggregations of smaller colonies. Despite being one of
How much variation in social parameters exists in native popthe best-studied social insects, we still know surprisingly little
ulations of species that can form supercolonies (e.g., colony
about the biology of Argentine ants, particularly in their native
size, queen number, intra- vs. intercolony genetic diversity, gene
range. From an evolutionary perspective, we often know even
flow among colonies)? Is there conflict over reproduction
less about species closely related to those that form supercolwithin supercolonies or are they as harmonious as Moffett
onies. For example, what characteristics are shared among sibimplies? Over what spatial scales are food and information exling species in the humile complex or are unique to the
changed (Heller et al. 2008)? These last 2 questions in particwidespread L. humile?
ular address whether or not supercolonies are effectively made
up of
aggregations
smaller
colonies.unicolonial.
Despite being one of
Key
words:
Argentineofant,
supercolony,
the best-studied social insects, we still know surprisingly little
about the biology of Argentine ants, particularly in their native
Address
correspondence
to A.V. Suarez.
E-mail:we
[email protected].
range. From
an evolutionary
perspective,
often know even
edu.
less about species closely related to those that form supercolonies. For example, what characteristics are shared among sibling species
in the humile
complex
are unique
to the
Received
14 January
2012; revised
14 or
January
2012; accepted
widespread
L. humile?
26
February 2012.
Key
Argentine ant, supercolony, unicolonial.
doi: words:
10.1093/beheco/ars050
Address
correspondence to A.V. Suarez. E-mail: [email protected].
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edu.
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accepted
duced Argentine
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26 February
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Heller
NE, Ingram
structure in unicolonial Argentine ants. Insectes Soc. 55:397–403.
doi:
10.1093/beheco/ars050
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B, Wilson EO. 1977. The number of queens: an important
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