Zoological Journal of the Linnean Society, 58: 297-308. With 1 figure
June 1976
Adaptive radiation and convergence in
subdivisions of the butterfly genus Heliconius
(Lepidoptera: Nymphalidae)
JOHN R . G . TURNER
Department o j Ecology and Evolution, Division ofBiologica1 Sciences,
State University o f N e w York, Stony Brook, New York 11 794, U.S.A.*
Accepted f o r publication July I975
The process of adaptive radiation and convergence, usually regarded as a feature of
macro-evolution, can be seen in the mimetic colour patterns of the butterflies within the
confines of the South American genus Heliconius. This can be shown by dividing the genus into
subgroups on the basis of adult, pupal and larval morphology: the theory that the mimicry
between species results solely from close systematic relationships is thereby refuted, as
members of the same morphological group can display widely divergent mimetic patterns, and
conversely mutual mimics may belong t o several different morphological groups. Various forms
of parallel and convergent evolution are thought t o account for the present pattern of mimicry;
the process is known to start even before full speciation has taken place. A new subgenus
( N e m d a ) is created t o contain three atypical members of the genus.
CONTENTS
. . . .
Introduction
History
. . . . .
Subgenera of Heliconius
Neruda subgen. nov.
Discussion
. . . .
Summary
. . . . .
Acknowledgements
. .
Note added in proof
.
References
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297
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307
307
INTRODUCTION
The hypothesis that evolution in the long term, that is over times exceeding
a few human generations, is governed by the same forces that are observable in
experiments and by field observation, is not open to direct experimental test.
But it would be open to more direct testing than is usually believed, if a group
Contribution No. 109 from the Program in Ecology and Evolution at the State University of New
York at Stony Brook.
297
298
J . R. G. TURNER
of organisms could be found in which some aspect of meso- or macro-evolution
had happened sufficiently rapidly to be seen within the confines of one genus,
within which artificial hybridization of geographical races, if not of full species,
was possible. A still more direct approach could be used if the characteristics
under study were of a known function (or demonstrable lack of it). Muellerian
mimicry in some South American butterflies fulfills these criteria. The function
of the mimicry is known to be mutual protection of the mimetic species against
their predators, because all are unpalatable and by sharing a common pattern
they reduce the load of predation, necessary for educating and for reeducating
predators, on all the species in the mimicry ring. The adaptive value of mimicry
has been demonstrated in many experiments (Rettenmeyer, 1970 for review).
Within the genus Heliconius the mimetic patterns of the butterflies have
undergone such rapid evolution that they show the pattern of adaptive
radiation of evolutionary lines, with the concomittant functional convergence
of members of different lines, which is usually thought of as characteristic of
evolution in the long term. The whole process of race formation, speciation and
adaptive radiation can be observed within the boundaries of this one genus.
Much is now known about the dynamics and genetics of the beginning of the
process, the formation of divergent mimetic races in a single species (Sheppard,
Turner, Brown & Benson, 1976; Turner, 1971, 1976). T o understand the
process as a whole, especially above the species level, we must first have a good
understanding of the systematics of this very difficult genus. In particular, it is
necessary to establish the natural subdivisions of the genus, in the hope that
these are, to some degree of approximation, groups of phyletically related
species. This paper formally defines one rather distinct group, in the context of
the process of adaptive radiation in the genus.
HISTORY
Mimicry between species within the same genus was not often noted by early
students of batesian and muellerian mimicry: it would hardly do to support a
controversial theory by citing resemblances that could be the result merely of
common ancestry, and the most convincing examples of mimicry are those
between different orders of insects, or between different kingdoms (resemblance of insects to twigs, or plants t o stones). But mimicry can in theory
occur between related species: the criterion is not whether the resemblance
results from convergence or from common ancestry, but whether or not it
protects the mimetic species.
In the genus Heliconius there is considerable muellerian mimicry between
species. Long ago Eltringham (1917) realized that this showed a curious
regularity: he divided the genus morphologically into two subgroups, and
found that the colour pattern of each species in the first subgroup could be
matched by a “mimic” in the second. Except for talking about “models” and
“mimics”, when it is clear that, because all tested species in the genus are
distasteful to birds (Brower, Brower & Collins, 1963), one has pairs of
muellerian comimics, neither of which can be regarded as the model,
Eltringham had correctly described the situation. But it is rather more
complicated than he thought, as some of his “species” in each subgroup were in
ADAPTIVE RADIATION I N HELICONIUS
299
fact races of m o very widespread polytypic species now called Heliconius
inelpomene and H. erato, and more detailed taxonomic studies have made it
apparent that the genus can be divided into more than two subgroups (Emsley,
1963 ; Turner, 1968).
Eltringham’s conclusions were disputed by Beebe, Crane & Fleming (1960),
who claimed from a systematic study of the early stages of the fourteen
Trinidadian species that the convergent or parallel mimics were in fact rather
closely related, and therefore resembled one another simply by common
ancestry .
SUBGENERA OF HEI.IC0NIUS
The genus Heliconius as recognized by Michener (1942) and Emsley (1965)
is a convenient unit for the general biologist. A good naturalist, according to
Linnaeus, knows all his genera (Cain, 1958); the large genus Heliconius is
recognizable to the butterfly enthusiast in the same way that the genus Morpho
is recognizable. Further subdivision becomes necessary for the study of
evolutionary patterns within the genus, and is also useful to the specialist,
particularly in view of the great use now made of the genus for studies in many
branches of biology (references in Turner, 1971; more recent studies include
Brown & Mielke, 1972; Brown & Benson, 1974; Ehrlich & Gilbert, 1973).
Small members of th genus, with short antennae, have long been placed in
Eueides, regarded by some as a subgenus (Michener, 1942; Emsley, 1965;
Turner, 1968), by others as a full genus (Brown & Mielke, 1972; Brown &
Holzinger, 1973; Neustetter, 1929; Stichel & Riffarth, 1905); assignment to
this group has been correct, except for the rather small Heliconius species H.
ricini and H. demeter which have often been erroneously placed in Eueides, the
latter under a bewildering variety of synonyms (Turner, 1966; Brown &
Benson, 197 5 ) . Recent studies of internal anatomy, karyotypes, chemistry,
life-history and behaviour have further defined the differences between these
groups, summarized in Table 1.
The remaining Heliconius can be split into a number of clusters of related
species, at least one of which is rather distinct. I t was initially noticed that
Heliconius aoede, while showing an adult morphology similar to that of other
Heliconius, had a pupa which was unlike other members of the subgenus and
rather similar to the pupae of Eueides, and a larva that was unique among the
known Heliconius and Eueides in lacking scoli on the head (Turner, 1968).
Further studies of this species by K. S. Brown, Jr indicate that while much of
its adult morphology corresponds with Heliconius, its early stages tend much
more to Eueides (Brown & Holzinger, 1973; Brown, 1973); de Lesse (1970)
found the haploid chromosome number to be 23, which lies between the
number 21, which is found in the great majority of the subgenus Heliconius,
and of 3 1 and above, normal for Eueides (Suomalainen, Cook & Turner, 1972).
Brown reports that the small white egg is laid in clusters, apparently on Dilkea,
an aberrant member of the Passifloraceae; this and further habits of the adult
are described by Brown (1973).
On these grounds a new subgenus is here created for Heliconius aoede, there
being no name of generic rank available. From their general appearance and the
3 00
J . R. G . TURNER
Table 1. Characteristics differentiating three subgenera of Heliconius. Adapted
from Brown & Holzinger (197 3)’ with additional information from Brown
(1973)
~
Character
Segments in female
foretarsi
Eueides
Neruda
Heliconius
four
five
five
Spermatheca duct
narrow
broad
broad
Signa of bursa
copulatrix
usually bent at a
right angle or more
not bent at a
sharp angle
usually bent at a right
angle or less, or absent
Antenna length
compared with iforewing radius
less
less
more
Haploid chromosome
number
over 30
21-32
21 in almost all species
(except the sapho group)
3-Hydroxykynurenine
as yellow pigment
absent
present
present
Egg (usually)
small, white
small, white
large, yellow
Head pattern of
mature larva
black, or with
stripes
black
black or yellow,
rarely striped
Scoli on head of larva
present
absent
present
Chrysalis hangs
horizontally
horizontally
vertically
Pollen-feeding
(imago)
absent, but feeds on
bird-droppings
absent
present
Eggs laid (usually)
ventral surface of
older leaves
growing bud or
young leaves
growing bud or
young leaves
close similarity of their internal anatomy to aoede (Emsley, 1965) it is clear
that H. metharme and H. godmani should be included in the subgenus, but as
no studies have been published in their early stages, the diagnosis is based only
on aoede. D’Almeida (1937) describes H. metharme as showing a curious
nervous behaviour when in flight, rapidly fleeing the approach of strange
objects. Recent work indicates that the haploid chromosome number in the
three species ranges from 21 (most races of aoede) to 32 (Brown, Emmel &
Soumalainen, unpubl.).
Linnaeus created Heliconius as a subsection of Papilio, to contain delicate
butterflies not suited as were the Danaids and Swallowtails, to being named
after the combatants from the Iliad; they were mainly named after muses,
graces and female deities (melpomene, egeria. vesta), Heliconius signifying
dwellers on Mount Helicon, and the group originally contained Phoibos
Apollon Musagetes himself in the butterfly now known as Parnassius apollo
(Papilionidae). Later authors have continued the association with poetry and
the arts by using names like lucretius, isolda, elsa, elvira, and aida. In
continuance of this tradition, and recalling that the butterflies are South
American, the new subgenus is named after the author of Alturas de Macchu
Picchu. Veinte Poemas de Amor, Residencia en la Tierra etc. Senor Pablo
ADAPTIVl? RADIATION I N HELICONICJS
301
Neruda graciously consented to the use of his name, although sadly he did not
live to see this paper written. *
Nemda subgen. nov.
Heliconius butterflies characterized by a singular wingshape, particularly the
broad triangular forewings, with very extensive friction patches in the male
(Fig. 1) (females having wings of more normal shape for their genus), by
antennae about half the length of the forewing, by a broad duct on the
spermatheca and the absence of a sharp angle in the signa of the bursa
copulatrix. 3-hydroxy-kynurenine is used as a yellow pigment, and the haploid
chromosome number is 21 to 32.
Figure 1. Silhouette of a male Heliconius aoede to show characteristic wing shape and unusually
large friction patches. (Drawing by Joyce Roe.)
The eggs are small, white and laid in clusters. The larva lacks scoli on the
head, and the pupa is bowed at the rear end of the abdomen, so that it rests
horizontally beneath its support; it lacks prominent head appendages, flanges
on the body, antenna1 spines and gold spots; the abdominal spines are slender
and arise from tubercles.
Type species. Migonitis aoede Hubner, 1816 (Verz. bekannt. Schmett., 12).
Needless to say, the gender of the new subgenus is masculine, despite its
ending.
The rest of genus Heliconius can be divided into subgroups recognizable by
adult morphology and, in so far as this is known, by details in the morphology
*
No volveris del fondo de las rocas.
N o volveris del tiempo subterrineo.
No volveri N voz endurecida.
N o volverin tus ojos taladrados . . .
Per0 una permanencia de piedra y de palabra:
la ciudad como un vaso se levant6 en las manos
de todos, vivos, muertos, callados, sostenidos
de tanta muerte, un muro, de tanta vida un golpe
de petalos de piedra: la rosa permanente, la morada:
este arrecife andino de colonias glaciales . . .
Hablad por mis palabras y mi sangre.
Alturas de Macchu Picchu
302
J. R. C. TURNER
of the pupa. From what is known at present, the only one of these groups
sufficiently distinct to be a candidate for subgeneric rank is the single species
Heliconius doris, which has a pupa lacking the gold spots, flanges and well
developed antenna1 spines of the other species, and which has the distinction of
being the only species with a marked colour polymorphism as an adult, the
only species with a marked morphological polymorphism as a pupa, and the
only species, apart from H. (N.) metharme, to produce blue colour not by
iridescence but by laying white scales over black. Its variable chromosome
number lies between Neruda and Eueides (Suomalainen, Cook & Turner,
1972). The tentative separation of this species into a separate subgenus Laparus
is maintained in this paper (Turner, 1968).
In summary, the subgenera, which for the present purposes are adequately
differentiated by Fig. 1 , Table 1 and the notes in the text, are:
Heliconius Kluk, 1780
Type species Papilio charitonia Linnaeus, 1767 designated by Hemming,
1933 (Entomologist, 66: 223).
Eueides Hiibner, 18 16
Type species Papilio isabella Cramer, 1781 through its subspecies Nereis
fulva dianasa Hubner, 1816, designated by Scudder, 1875 (Proc. Am.
Acad. Arts Sci., 10: 164).
Laparus Billberg, 1820
Type species Papilio doris Linnaeus, 1771 designated by Hemming, 1934
(Entomologist, 67: 37).
Neruda subgen. nov.
Type species Migonitis aoede Hiibner, 1816
Although one of these names is frequently used as a separate genus, it is clear
that some authorities will continue to treat the whole group as a single genus; it
is important that in creating new names for species and races homonyms should
not be made within Heliconius in the broad sense, as changes in the generic
classification will make the nomenclature at the species level unstable. This
situation already exists for the nine names listed in Table 2. Replacement
names are not proposed, and should not be proposed until the infraspecific
Table 2. Homonyms created by the fusion of Meliconius and Eueides (for
citations see Neustetter, 1929). Attribution of subspecies t o species follows
modern practice, not necessarily the original combination
Subgenus Heliconius or Neruda
Subgenus Eueides
clysonymus apicalis J & K,1917'
melpomene ecuadorensis Neustetter, 1908.
erato fuliginosa Riffarth, 1907
numata f. gracilis Riffarth, 1907
burneyi huebneri Staudinger, 1896
aoede lucretius Weymer, 1890.
melpomene f . Pluto Staudinger, 1896.
melpomene f. riffarthi Stichel 1906
[melpomene x cydnol seitzi Neustetter, 1916
lampeto apicalis (Rober, 1927)
isabella ecuadorensis (Strand, 1914)
lampeto fuliginosa (Stichel, 1903).
aliphera gracilis (Stichel, 1903).
isabella huebneri (MCnCtrits, 1857)'
tales f. lucretius (Zikan, 1937)
eanes f. Pluto (Stichel, 1903)
eanes f. riffarthi Stichel, 1903).
isabella seitzi (Stichel, 1903).
* Senior homonym
ADAPTIVE RADIATION I N HELICONIUS
303
classification of the whole genus has been overhauled. For all names except
possibly ecuadorensis or hrtebneri, at least one of each pair will certainly turn
out t o be an infrasubspecific variety, an interracial hybrid, or an interspecies
hybrid, and less confusion will ensue from keeping the names, appropriately
sunk, than by replacing them. Although one of the two uses of ecuadorensis
and hucbneri might require a replacement under strict application of the Rules,
neither will ever be raised t o full species, and in practice there will be no chance
of confusing them.
Within the larger subgenera (Eueides and Hdiconius) it is possible t o
recognize further clusters of species. I t is not recommended that these be
named, even when the subgenera are given full generic rank, as there are too
many of them for Latin names to be remembered by any but the most ardent
specialist; they can conveniently be referred to by the name of the most
prominent species (as erato-group, rnelpornene-group), or as in this paper by
numbers.
DISCUSSION
Once the genus Heliconius has been divided into its subgenera and further
subgroups, shown vertically in Table 3 , it is possible to demonstrate very
clearly the pattern of adaptive radiation and convergence mentioned in the
introduction by tabulating the colour patterns of the species (horizontally in
Table 3). If morphology and colour pattern had followed the same evolutionary course and related species had similar colours because of common
ancestry, then few cells of the table could be filled with the names of species.
For instance all the blue species should be in a single morphological group. As
it is reasonable to suppose that the mimetic colour patterns are much more
likely to undergo convergent evolution, and more rapidly, than are morphological characters, this table shows that there has been considerable adaptive
radiation of the colour patterns within each morphological group. Thus the
three members of the subgenus Neruda, presumably derived from a single
common ancestor, have radiated to join three mimicry rings (as groups of
species with similar patterns are called), the red and yellow (radiate) ring, the
blue and yellow ring, and one of the rings which mimic various Ithomiid
butterflies.
I t has been argued that this process of radiation and convergence starts at the
earliest possible stage in evolution, during the formation of allopatric races
(Sheppard e t al., 1976; Turner, 1976). The beginning of the process is shown
by pairs of species that have widely divergent races within each species, each
race of the one exactly matching a sympatric race of the other; H. melpomene
and H. eruto are the best example of this, and their parallel variation is partly
shown in Table 3 by their each appearing in two columns (for a colour
illustration, see Turner, 1975). The force causing divergence of the races is
held t o be considerable change in the faunas of the forest “islands” to which
the species were confined during the last glaciation (Haffer, 1969), causing the
species t o “switch” from their original pattern to a new one mimicking the
most abundant or distasteful local species (Brown, Sheppard & Turner, 1974).
As race formation can presubably lead t o species formation, it is held that the
parallel series of species shown in Table 3 are the result of repeated cycles of
304
J . R. G . TURNER
Table 3 . Classification of some Heliconius species by morphology anc
Orange and yellow Red, sometimes
(radiate)t
yellow barst
Subgroup
Red (blotches)
and yellow
Blue and yellow
procula (Venezuela)
tales (Colombia)
eanes (black)
Eueides
tales
eanes (red)
-
Neruda
aoede’
-
-
metharme
Laparus
doris (red)*
-
doris (red)
doris (blue)*
la
erato‘
era to *
hermathenu (Faro)
hortense‘
ClysOnymUS*‘
leucadia
Sara *
sapho ( E . Andes)
Ib
demeter’
-
ricini*
[la
me/pomene*‘
timareta (form)
melpomene*
timareta’ (form)
timareta (form)
Ilb
elevatus
hesc kei *
-
-
111
xanthocles*
-
-
IV
hurneyi.
egeria
astraea
-
wallacei*
Heliconius
’
-
Notes. This table includes, o u t of around 54 species of Heliconius (sensu Into) now recognized (Brown &
Mielke, 1972), 31 species whose systematic position is well established, preferably with descriptions of
the early stages (marked *) (Beebe, Crane & Fleming, 1960;Turner, 1968; Brown, 1972; Brown & Mielke,
1972; Young, 1973; Brown & Holzinger, 1973; Brown & Benson, 1975a, 1975b; Turner, unpubl. for H.
atthis).
Addition of the remaining species would n o doubt introduce subgroups intermediate between those
shown, which are rather distinct, but would not alter the general conclusion.
The pattern classes are also rather distinct, but d o embrace racial variation, usually in parallel, of the
included species; this applies particularly t o those marked t. The “blue ane white” and “black and white”
groups contain races with the white changed t o yellow, and some of the “blue and yellow” lack the blue
iridescence. The groups marked $ are heterogeneous and include several different patterns. Where the
same species appears in several pattern groups it has widespread races (or morphs) belonging t o all of
them; locations are given only for very restricted races.
glaciation during the quaternary, the earlier cycles having now led to full
speciation.
In that event, there are several patterns of evolution which could account for
the arrangement of species in Table 3. First, parallel evolution. Two species,
initially muellerian comimics either by common ancestry or convergence
remain comimics during several cycles of divergent race formation and
speciation, thus “budding” several pairs of mimetic species. There is genetical
evidence that the parallel variation between Heliconius groups Ia and IIa has
arisen in this way (Sheppard et al., 1976). Second, convergence. A species
changes its pattern from one mimicry ring to another. This may produce empty
cells in the table (an effect produced also by extinction), or cause several
species to occupy the same celI, or cause a column (pattern) to disappear
altogether. Brown & Benson (1976) describe it at the race level in H.
hermathena and the non-mimetic species H, charitonia has apparently changed
ADAPTIVE RADIATION IN HELICONIUS
305
colour pattern (revised and expanded from Turner, 197 1 , 1976)
Blue and white
Black and white
Tiger
ithomiinet
Other ithomiine Black and
or acrarineg
yellow A
isa bella
lampeto
procula '
pavana'
vibilia2
-
godnianih
Black and
yellow B$
-
-
-
eleuchia
eraro (Cauca)
sapho
antiochus
sapho (Ocafia)
-
peruviana'*'
-
-
-
-
cydno.
-
cydno'
atthis.
pachinus
nutrererid" '
-
luciana (Roraima)
ethilla'
numata
nattereriQ
hecale.
-
-
luciana '
(Amazonas, Venezuela)
~
doris' (green)
doris' (green)
hewitsoni
sara (Chiriqui)
charitonia"
hermathena*'
-
'
Mutually allopatric, but mostly sympatric with red doris.
""4Pairs of mimics within this heterogenous class of patterns.
Mimic Actinore, and mimic Elzunia.
'All allopatric, except for charitonia and green doris. There are grounds for regarding this as the
primitive pattern for groups I and I1 (see text).
Life-history not published; known for two races to be identical with the "red sometimes yellow bars"
races.
'Mr Gordon Small of Balboa tells me that within the rather confined distribution of hewitsoni and
pachinus the green form of doris becomes much yellower, and is consequently an adequate mimic of
the other two when in flight (also Benson, 1971).
'Both mimics of H. hecalesia and the associated ithomiines.
Usually regarded as a subspecies of charitonia but shown by recent fieldwork by the author to be
sympatric, apparently without hybrids, with typical charironia about 800 m u p the Andes above Santo
Doming0 de 10s Colorados, Ecuador.
'
to join an Ithomiid ring in western Ecuador, speciating in the process (H.
peruuiunu). Third, reciprocal convergence. Suppose that the ancestral species
of, say, Nerudu, had a red and yellow pattern, and that the ancestral species of
some other group had a blue and yellow pattern. If Nerudu became the
dominant species in one forest "island" it would cause the other to switch to
the red and yellow ring, and if the reverse were the case in some other "island"
Nerudu would there switch to the pattern of the dominant blue and yellow
species. Speciation would produce parallel pairs of species. Again, there are no
proven examples, but this or the effect before it must have taken place, as the
patterns of warning coloured species are subject to strong normalizing selection
(Benson, 1972) and can only change from one mimicry ring to another in this
way (Sheppard et ul., 1976).
Fourth, allopatric speciation without divergence of pattern. I t is to be
expected that in the absence of selection to switch to another mimicry ring, or
22
3 06
J . R. C.. TURNER
in the absence of the appropriate mutations, allopatric populations of a species
will retain the same pattern, and while it is clear from melpomene and erato
that the beginning of adaptive radiation may precede speciation, it is also
extremely likely, unless alteration of the colour pattern is the only possible
isolating mechanism in these butterflies (and the existence of sympatric and
similarly coloured relatives refutes that suggestion), that speciation may
proceed without the divergence of pattern. Thus hortense and clysonyrnus
are allopatric relatives in group I, which should probably be regarded as
good species, with basically the same pattern. If they became sympatric, they
would have to be regarded as comimics by retention of an ancestral pattern.
The closely similar sympatric sibling pair, melpomene and elevatus may be an
example of this. Fifth, speciation with slight divergence, followed by
reconvergence. If two mimicry rings are so similar that predators sometimes
mistake one for the other, the rings will simply slowly converge to a common
pattern (Sheppard et al., 1976). Thus allopatric speciation followed by
sympatry could involve slight divergence of the patterns, which would then
reconverge. The morphologically similar sympatric pair erato and demeter may
be a case of this.
Sixth, one might see non-mimetic resemblance between two not very closely
related and allopatric species. This occurs in Table 3 in the last column (black
and yellow) and is held by Brown (1972) and Sheppard et al. (1976) to show
that the species have retained the pattern by common ancestry from the
remote past (as non-mimetic patterns will evolve more slowly than mimetic
ones) which means that this pattern is close to that of the common ancestor of
groups I and 11, and possibly of the whole subgenus Heliconius. A similar
consideration of the subgenus Eueides suggests that the ancestral pattern may
have been of black and orange longitudinal stripes (not listed in Table 3), now
exhibited by the largely allopatric species lybiu, emsleyi and libitina (for the
last two, see Brown, 1975). Interestingly enough, this striping has a similar
distribution on the wings to the yellow striping of the supposed ancestral
pattern of the subgenus Heliconius, and is very similar to the orange striped
pattern of the related non-mimetic species Dryudula phaetusu.
Reconstructing the actual course of evolution will of course be extremely
difficult, if not totally impossible, but it is now clear that the evolution of
mimicry in the group follows a pattern which is neither exactly that proposed
by Eltringham (19 17)-convergence or parallelism between two subsections of
the genus-nor that of Beebe, Crane & Fleming (1960), who thought that the
resemblances mainly resulted from close systematic relationships. As is often
the case with controversies, the truth is more complicated and lies between the
two extremes. There is in fact extensive parallelism and convergence, but it
takes place between many more than two subdivisions, and plainly arises both
from convergence and from the retention of ancestral patterns. In fact the most
spectacular case of parallelism, that of melpomene, erato and their associated
species, results from parallel evolution between two separate, speciating
evolutionary lines, which may originally have been mimics by common
ancestry; such a phenomenon fits neatly into neither of the conventional
categories “convergence” and “taxonomic propinquity.”
ADAPTIVE RADIATION IN HELZCONIUS
307
SUMMARY
The genus Heliconius can be subdivided into around four rather distinct
subgenera, one of which is named in this paper, and then into a number of
other groups which have not been and should not be formally named. The
groups are distinguished by the morphology of the adults and of the early
stages, and by behaviour.
Subdivision of the genus in this way shows that groups of related species
have undergone wide adaptive radiation in their colour patterns, converging
with members of other groups under selection for muellerian mimicry.
Reciprocal convergence between two species in different parts of their range,
and parallel evolution between two already mimetic species in the period in
which they themselves speciate, will produce series of paired mimetic species
such as are found in the genus. Speciation with little divergence of pattern, or
reconvergence of pattern, will produce closely related mimetic species.
Resemblance between non-mimetic species which are allopatric is likely to
indicate that they have retained the pattern from a common ancestor.
The beginning of the radiation of colour pattern can be seen in some species
in the divergence of allopatric races; Heliconius thus presents the process of
evolution from race formation to adaptive radiation, compressed within the
confines of a single genus.
ACKNOWLEDGEMENTS
I am very grateful t o Mr N. D. Riley for searching for the existence of prior
uses of the name Nerudu at the generic level, and to Dr K. S. Brown, Jr,
Professor A. J. Cain and Professor P. M. Sheppard F.R.S. for criticism and for
correspondence on topics related t o this paper.
I gratefully acknowledge financial support in the form of seed-grants from
U.S. Public Health Service Biomedical Sciences Support Grant 5 S05RR07067-08 (awarded t o the State University of New York at Stony Brook),
the Graduate School of the State University of New York at Stony Brook, and
the Research Foundation of the State University of New York, and in the form
of a major grant from the National Science Foundation (number B039300).
NOTE ADDED IN PROOF
The first instar larvae of Heliconius (Neruda) aoede have now been observed from eggs obtained by Dr
K. S. Brown at Leticia (Amazonas, Colombia). They have very long chaetae on the back (around three
times the height of the head capsule) and are pale yellow with a brown-grey head, thus resembling the
first instar larvae of Heliconius (Eueides) aliphera and differing considerably from those of the subgenus
Heliconius (Beebe, Crane & Fleming, 1960).
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