Chromosomal rearrangements maintain a
Mathieu Joron1,2,3, Lise Frezal1*, Robert T. Jones4*, Nicola L. Chamberlain4, Siu F. Lee5, Christoph R. Haag6, Annabel Whibley1,
Michel Becuwe2, Simon W. Baxter7, Laura Ferguson7, Paul A. Wilkinson4, Camilo Salazar8, Claire Davidson9, Richard Clark9,
Michael A. Quail9, Helen Beasley9, Rebecca Glithero9, Christine Lloyd9, Sarah Sims9, Matthew C. Jones9, Jane Rogers9,
Chris D. Jiggins7& Richard H. ffrench-Constant4
of adaptive variation, providing integrated control of complex
adaptive phenotypes1. Polymorphic supergenes, in which specific
combinations of traits are maintained within a single population,
and snail morphology6. Understanding the evolutionary mechan-
isms that generate these co-adapted gene sets, as well as the mode
of limiting the production of unfit recombinant forms, remains a
morphs in the polymorphic mimetic butterfly Heliconius numata
are associated with different genomic rearrangements at the super-
gene locus P. These rearrangements tighten the genetic linkage
between at least two colour-pattern loci that are known to recom-
bine in closely related species9–11, with complete suppression of
recombination being observed in experimental crosses across a
tions, notable patterns of linkage disequilibrium (LD) are observed
across the entire P region. The resulting divergent haplotype clades
and inversion breakpoints are found in complete association with
at known wing-patterning loci have become locked together in a
actsasasimple switch between complex adaptivephenotypes found
can have a central role in the coexistence of adaptive phenotypes
involving several genes acting in concert, by locally limiting recom-
bination and gene flow.
The origin and maintenance of adaptive multi-locus polymorphism
in the face of recombination is a long-standing puzzle in evolutionary
linkage that maintains specific combinations of alleles at neighbouring
genes1–6. A notable illustration is provided by polymorphic mimetic
butterflies, in which several discrete forms, each resembling a different
model, are maintained in sympatry. Examples include Batesian poly-
morphism in Papilio dardanus5,14and Papilio memnon3and Mu ¨llerian
polymorphism inthe neotropicalspecies Heliconiusnumata4,15. In each
plex phenotype which can involve modifications of wing pattern and
sharp fitness peaks corresponding to locally abundant wing patterns,
individuals with intermediate, non-mimetic phenotypes16.
Theoretical debate has centred on the constraints imposed on super-
gene evolution by genomic organization, specifically whether loci must
be tightly linked from the outset or whether the association between
elements can be acquired, either gradually or in a single mutational
step7–10,16–19.Chromosomalrearrangements, whichcan bringgenes into
closer physical association and influence local recombination, offer one
route through which supergenes may be assembled from more loosely
linked components7,8,17–19. Although there are many cases of poly-
morphic inversions associated with adaptive variation12,20, variation is
tions, and effects on local adaptation are cumulative. In contrast, super-
genes are characterized by a Mendelian switch between clearly defined
combinations of traits in populations. Here we investigate the genomic
and identify a key role for structural variation in strengthening and
maintaining allelic associations within the supergene.
tions and each is an accurate mimic of one of several available model
is controlled by a specific allele at P with precise allelic dominance4,15
*These authors contributed equally to this work.
1CNRS UMR 7205, Muse ´um National d’Histoire Naturelle, CP50, 45 Rue Buffon, 75005 Paris, France.2Institute of Evolutionary Biology, University of Edinburgh, Ashworth Laboratories, King’s Buildings,
of Exeter, Cornwall Campus, Penryn, Cornwall TR10 9EZ, UK.5Department of Genetics, Bio21 Institute, University of Melbourne, 30 Flemington Road, Parkville, 3010 Victoria, Australia.6Department of
Biology, Ecology and Evolution, University of Fribourg, Chemin du Muse ´e 10, CH-1700 Fribourg, Switzerland.7Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK.
8Smithsonian Tropical Research Institute, NAOS island, Causeway Amador, Panama ´, Repu ´blica de Panama ´.9The Wellcome Trust Sanger Institute, Hinxton, Cambridge CB10 1HH, UK.
Melinaea : models
Heliconius melpomene : monomorphic, parapatric subspecies
DominantIntermediate dominant classesRecessive
Heliconius numata : polymorphic mimic, sympatric morphs
Figure 1 | Supergene alleles and mimicry polymorphism in H. numata.
Polymorphic forms of H.numata each mimic different models in the distantly
valleys; Y, Yurimaguas and Amazon lowlands) harbour different mimicry
assemblages15; dominance (,) is nearly complete between forms within each
region, but is incomplete (,) between certain pairs of alleles from parapatric
regions. In all other species studied in the genus Heliconius, wing pattern is
controlled by several large-effect loci on different chromosomes. In
H.melpomene the HmYb–HmSb–HmN complex is situated in the orthologous
position to the H.numata P supergene9. LG, linkage group.
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(Fig. 1). Rare non-mimetic individuals that combine pattern elements
binants, confirm the existence of several functional elements in the
locus. The genomic position of P was previously shown to correspond
distinct wing-pattern elements in geographical races. Other unlinked
wing-pattern loci in related species do not have large effects on
By fine-scale linkage mapping and positional cloning, we identified
a chromosomal interval of about 400kilobases (kb) containing the
H.numata P supergene, defined by the absence of crossing over in
366 progeny from six broods (Fig. 2a). The orthologous region in
H.melpomene shows notable rates of recombination and contains
(cM) apart11. Although genome-wide estimates of recombination rate
in Heliconius are not available, markers adjacent to P, markers else-
where on linkage group 15, and markers in other linkage groups
over (chi-squared test of independence, P53.831026), consistent
with severe suppression of recombination at P in H.numata.
To examine the gene content and genomic organization of the
supergene, we sequenced an approximately one-megabase (Mb)
region centred on P by screening a bacterial artificial chromosome
(BAC) library prepared from a mixture of individuals from a single
polymorphic population of H.numata (Supplementary Table 2).
Colinearity and gene content was generally conserved with H. melpo-
mene11, buttwo BACsoverlapping the P intervalshoweddistinct gene
orders, both different from the order seen in H.melpomene (Figs 2a, 3
and Supplementary Fig. 1). A third gene order, corresponding to the
H.melpomene reference, was detected by PCR (see below). Gene ori-
entation near the breakpoints on the H.numata clones indicated a
minimum of two rearrangement events compared to the reference,
putatively involving 31 genes: a 400-kilobase (kb) segment containing
18 genes from HN00023 to HN00040 (breakpoint BP1), and a 180-kb
segment containing 13 genes from HN00041 to HN00053 (breakpoint
BP2) (Fig. 3a and Supplementary Fig. 1). The altered gene orders at P
and 4), as well as between more distantly related Heliconius species22.
by about 100million years of evolution, share a generally conserved
(–10 × log
Variable SNP positions
HN00024 / LRR
(34 as Psil/Paur heterozygotes)
(34 as Psil
P P /P
(34 as Psil/Paur heterozygotes)
sequence (H. melpomene)
H. numata P locus tilepath
recombinants with P
1 1 1 111111222
0 000 000000000124402
Figure 2 | Fine-scale mapping and nucleotide variation at the P supergene
in H.numata. a, Fine-scale linkage mapping of the supergene P (indicated by
red arrows) to the interval bounded by genes HN00020 and HN00041.
Recombinants were observed in crosses totalling 366 individuals. Blue arrows
indicate the position of the recombining loci HmYb and HmSb in
H.melpomene11. HmN, which is known to be part of this cluster of loci, is not
fine-mapped in H.melpomene9,11. Coloured blocks represent annotated gene
regions on forward and reverse strands (see Supplementary Fig. 1 and
Supplementary Table 3 for details). b, Association of SNP variation with
mimicry polymorphism in a sample of 25 silvana and 34 aurora/arcuella
individuals from a single population. Markers genotyped across
rearrangements BP1 (pink) and BP2 (blue) show perfect association of SNP
variation with wing pattern. No association was found in the flanking region
from markers Fox (Hn00106) to BmSuc (Hn00019), or at 12 unlinked loci
(green). The association decays more slowly in the direction of loci Bm5536
(GCP), Bm5586 (NudC) and Bm5593 (Srp68). c, LD heat map. Perfect LD
(genotypic correlation coefficient r251) is found across 580kb spanning the
BP1 andBP2 rearrangements (n559). LDdecaysrapidlyoutside thisinterval,
although strong within-marker LD remains at HN00021. Markers that are
marker LRR (Hn00024) in the Yurimaguas population, coloured according to
are in complete association with wing pattern, taking into account dominance
P, and across the Amazon basin, but not for genes flanking P or in unlinked
regions (Supplementary Figs 4 and 6).
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evolution of this locus in the H.numata lineage.
The results from BAC-clone sequencing were extended to natural
lected in the field (Fig. 3a and Supplementary Table 5). Long-range
PCR analyses of 31 individuals of four morphs revealed a complete
association between alternative rearrangements and specific wing-
pattern phenotypes (Fig. 3b). Rearrangement BP1 was found in every
H.numata bicoloratus and in no other morph, as expected for the
forms (aurora and tarapotensis). All recessive silvana individuals were
BP0 homozygotes, confirming that the reference gene order segregates
in H.numata populations. Some individuals with intermediate and
dominant alleles had breakpoints that were lower in the dominance
series, reflecting their heterozygosity. To confirm the association on a
were performed on 156 individuals of six major morphs (Fig. 1 and
Supplementary Tables 5–7). Short-range assays were highly consistent
with long-range assays (Supplementary Table 6). Natural populations
thus harbour at least three chromosomal arrangements in tight asso-
ciation with wing-pattern phenotypes. A short-range PCR product
from BP1 was not amplified in two of the 32 bicoloratus individuals
tested. This could reflect PCR failure due to sequence variation at BP1,
or it may indicate that the BP1 breakpoint is not directly causative of
the bicoloratus phenotype, despite being strongly associated with the
crosses operates at the population level, we estimated LD between
nucleotide positions in and around P. A notable pattern of long-range
survey of 17 markers sequenced in 59 individuals from the poly-
morphic population near Yurimaguas (Figs 1 and 2c). Complete LD
was found between high-frequency single nucleotide polymorphisms
(SNPs) across the 400-kb P interval, showing that long-range haplo-
types are maintained across the supergene. This haplotype structure
decaysrapidly outside P:flankingmarkerslack thehaplotypesegrega-
tion found within P and show comparable levels of LD to the levels
seen in 12 unlinked markers (Fig. 2c and Supplementary Fig. 3).
Furthermore, within P, complete association was found between the
divergent haplotypes and wing-pattern alleles. All recessive silvana
individuals were homozygous for 39 SNPs in six genes across the
for the alternative nucleotides (Fig. 2b, Supplementary Fig. 4 and
immediately outside P (Fig. 2b and Supplementary Figs 4 and 5).
Therefore, the divergent haplotypes associated with wing-pattern
alleles seem to be confined within the boundaries of the polymorphic
rearrangements and the position of the supergene.
Finally, to confirm that the haplogroups are associated with pheno-
lation of H.numata from French Guiana, situated 2,900km from Peru
but harbouring phenotypically similar morphs (silvana and numata;
Supplementary Table 5)4. The same two haplotype groups were found,
and breakpoint PCR and haplotype clades were perfectly associated
with corresponding phenotypes in both locations (Supplementary
Fig. 6 and Supplementary Table 6). The association between mimicry
polymorphism, local rearrangements and divergent haplotype blocks
therefore seems to be conserved across the Amazonian range.
Our results show that the supergene is characterized by a 400-kb
chromosomal block that is sharply structured into distinct haplotype
clades separated by 1–4% divergence. These clades correspond to dif-
inance and are associated with the chromosomal rearrangements
(Fig. 2d and Supplementary Figs 3 and 4). This situation stands in
stark contrast to the related species H.melpomene and H.erato, in
which several independent wing-patterning loci are under directional
selection, and in which markers surveyed in the orthologous region
showed no fixed nucleotide differences between colour-pattern races,
and no long-range LD10,24. The P supergene architecture, associated
H.numata4,15, is thus evolutionarily characterized by non-recombin-
known to recombine in other species of the clade10,24.
In summary, the four strands of evidence, namely fine-scale com-
parative mapping, association of three chromosomal arrangements
with morphs, SNP–phenotype association at P, and long-range LD
Figure 3 | Chromosomal rearrangements associated with the supergene in
natural populations. a, Comparison of the gene orders found in the
H.numata BAC library and wild populations. The rearrangements involve the
400-kb segment from genes HM00023 to HM00040 (ERCC6) (BP1, clones
24I10 and 45B17), and the adjacent 180-kb segment from gene HN00041
Genes closest to the breakpoints are shown. b, Long-range PCR assays across
alternative breakpoints(BP0,BP1 andBP2)inwild populationsshowa perfect
association of the polymorphic gene orders with mimicry variation in four
morphs from natural populations of Eastern Peru15, following the dominance
relationships (Fig. 1). The Yurimaguas population segregates primarily for
silvana and aurora/arcuella forms, associated with BP0 and BP2, respectively.
The Tarapoto population segregates mainly for tarapotensis and bicoloratus
forms, associated with BP2 and BP1, respectively. This population also
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and divergent haplotype clades, all indicate that the rearrangements
lock together distinct elements involved in wing-pattern evolution,
providing long-awaited evidence for a situation that may apply to the
species10,11can become locked together in others. Our results highlight
way to the study of their functional integration.
in the elements of pattern variation in H.numata, a goal hindered by
hotspot of adaptation in several other species26, including the melanic
to assortative mating and speciation in other Heliconius species28–30.
Unravelling the genetic nature of the elements that contribute to the
supergene will therefore be key to understanding the mechanisms
and sequence of events underlying the clustering of adaptive traits in
rearrangements that are associated with ecological divergence.
A BAC library was screened with radiolabelled probes derived from BAC end-
sequences during chromosome walking. Clone sequences, obtained by capillary
sequencing, were annotated with the aid of a Roche 454-sequenced cDNA library
from the developing wing11. Genomic sequences were aligned to a H.melpomene
reference11to detect chromosomal rearrangements. Crossover events were fine-
mapped using broods described elsewhere9. Recombination estimates from other
using markers separated by known physical distance.
PCR-based diagnostics for the rearrangement breakpoints BP1 and BP2 were
designed from H.numata BAC sequences. BP0 was designed from the reference
H.melpomene sequence. Long-range PCRs were primed in exons flanking each
breakpoint, and verified by sequencing. Short-range PCRs were primed closer to
the breakpoints in unique intergenic regions (Supplementary Table 7).
Genetic markers were sequenced by capillary sequencing. LD was estimated
from unphased sequences using genotypic correlation tests between all pairs of
variable sites. The association between wing-pattern and SNPs was tested using
Fisher’s exact tests, taking into account the dominance hierarchy of wing-pattern
alleles. Haplotype networks were constructed by parsimony using Network.
Full Methods and any associated references are available in the online version of
the paper at www.nature.com/nature.
Received 14 March; accepted 28 June 2011.
Published online 14 August 2011.
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Supplementary Information is linked to the online version of the paper at
Acknowledgements We thank M. Blaxter and D. Charlesworth for advice throughout
the study; The GenePool and S. Humphray for DNA sequencing; S. Kumar and
A. Papanicolaou for bioinformatics support; M. Beltra ´n, A. Bulski, M. Veuille and the
Botanique-Entomologie-Mycologie molecular facility (BoEM) for laboratory support;
with butterfly rearing, fieldwork and collecting permits; and the Peruvian National
Institute of Natural Resources (INRENA) for granting collecting and export permits
‘Nouragues Research Grant’. This work was supported by an EMBO long-term
Society University Research Fellowship (516002.K5917/ROG), a CNRS grant (ATIP
Biodiversite ´ 2008, France) and a European Research Council Starting Grant (ERC-Stg
Trust grant (F/00144AY) to R.H.ff.-C., and a Royal Society University Research
Fellowship and a Leverhulme Research Leadership grant to C.D.J.
Author Contributions M.J., C.D.J. and R.H.ff.-C. designed the study and contributed to
all stages of the project. M.J., L. Frezal and R.T.J. performed the principal experiments
and data analysis, with assistance from N.L.C., S.W.B., S.F.L., M.B., C.S., L. Ferguson,
C.R.H., A.W. and P.A.W. BAC clone sequencing was carried out by C.D., R.G., C.L., R.C.,
H.B.,S.S., J.R.,M.C.J. andM.A.Q.M.J., A.W., C.D.J.andR.H.ff.-C.co-wrotethe manuscript
with input from all authors.
Author Information GenBank accessions for BAC clone sequences: FP885863,
FP476061, FP565803, FP476023, CU856181, FP885878, FP476047, FP885857,
CU856182, CU655868, FP885879, FP885861, FP885880, FP885855, CU914733,
FP475989, CU655869, CU914734, CU633161, CU638865, CU856175, FP884220
and FP236755. Accessions for 1364 marker sequences: JN173798–JN175161.
Reprints and permissions information is available at www.nature.com/reprints. The
the online version of this article at www.nature.com/nature. Correspondence and
requests for materials should be addressed to M.J. (email@example.com).
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the forms bicoloratus, tarapotensis and arcuella. The BAC library has an estimated
119-kb average insert size and 37 coverage of the 319-Mb genome. It was printed
the orthologous genomic sequences from an H.melpomene BAC library9,11. The
BAC library was also fingerprinted by restriction digest, and overlapping clones
were predicted from analysis of a fingerprinted contig (FPC) database. Fifty-three
BAC clones were identified and tested for positive amplification of the original
probes. Nineteen H.numata clones were sequenced by the Wellcome Trust
Sanger Institute to high-throughput-genomic (HTG) phase 3 quality, totalling
2.9Mb of overlapping genomic sequence. Because of the multiple chromosomal
arrangements found in this region, and the fact that the clones sequenced come
fromchromosomes with differing geneorders asa consequence, itisimpossibleto
reconstruct a single linear tilepathofclones atthis stage. Onthe basis ofreciprocal
show different gene orders. A gap in the BAC chromosomal walk, estimated to be
approximately 150kb, remains between clones 7C9 and 14K13 despite extensive
screening of the library. However, the gene markers ARP-like (Hm00028) and
Pros54 (Hm00030), predicted from the reference Heliconius sequence to lie in the
the gap, indicating the gene content of the gap is probably conserved. Two addi-
tional contigs of clones were identified and sequenced approximately 350kb and
900kb from the end of the tilepath further down the chromosome (Fig. 2a and
Supplementary Table 2). Sequence similarity was plotted using the software
tary Fig. 2).
Linkage mapping. Male-informative markers were used to score crossing over
events between markers linked and unlinked to P. Female Lepidoptera have
achiasmatic meiosis, so crossing over only occurs during gametogenesis in the
male parent. Thirty-six PCR-based markers were designed from BAC sequences
and genotyped by visualization of differences in amplicon size, by restriction-
six mapping families (B377, B465, B472, B502, B523 and A298 (refs 9, 11)). This
was used to circumscribe the P supergene and orientate the tilepath by recom-
bination. Special emphasis was given to the regions near the first crossover on
either side of the supergene, for a precise positioning of the mapping boundary.
The three recombinants with P on one side, and two recombinants on the other
side, ensured that P was circumscribed and in full linkage with markers in an
interval estimated to be about 400kb (using a 0.92 scaling factor for H.numata
versus H.melpomene genomic sequence, on the basis of sequences available for
this region). The same procedure was used to score recombination events in
unlinked regions using two sequenced BAC clones (bHN20L19 and bHM7E22)
tionwereperformedasdescribedelsewhere11. Briefly,annotationand genepredic-
tions in all sequenced BACs (Supplementary Fig. 1 and Supplementary Table 3)
were carried out with the Maker annotation pipeline33, using 600K expressed
sequenced tags generated with Roche 454 FLX pyrosequencing (200-base average
read length) and assembled using the Mira assembler34to yield 24,992 objects.
stages from the Peruvian populations used throughout this study. Large variations
in non-coding content, as well as in the presence and identity of transposable
elements, were noted between clones within H.numata (Supplementary Table 4),
causing some H.numata clones (for example, 14K13) to show a higher overall
similarity to the orthologous H.melpomene sequences (bHM29B7) than to other
orthologous H.numata clones (46M23 and 38G4). This indicates that the two
H.numata chromosomal segments with differing gene orders may be anciently
Sequencing and breakpoint analysis. Annotation of the BACs was used to
identify exons within and outside the P mapping interval; exon markers were
tary Table 8). Unlinked markers were chosen following the method in ref. 35. A
containing P, plus 13 amplicons on unlinked chromosomes, were sequenced in
48–144 individuals (Supplementary Table 5) from a polymorphic population in
eastern Peru. This populations segregates predominantly for the forms silvana
and aurora (including sub-variants isabellinus and elegans). In subsequent ana-
lyses, we combined the auroravariants under the single class aurora, because the
numerous phenotypic gradations that are found between these forms contrast
the rearrangement breakpoints and the absence of diagnostic nucleotide differ-
ences also indicated that these variants could be combined.
Breakpoint PCR assays were carried out with primers designed from exonic
sequences on either side of each breakpoint (Supplementary Table 7). Fragments
were amplified from 31 individuals with four different wing patterns (bicoloratus,
tarapotensis, aurora and silvana) using long-range PCR (Qiagen) following the
A second, larger sample of 201 individuals (including161from Peru and 40 from
French Guiana) was assayed by standard (short-range) PCR amplification
(Fermentas DreamTaq) using primers positioned closer to the breakpoints in
unique non-coding DNA (Supplementary Table 7). Capillary sequencing of mar-
kers and breakpoint assays was performed on an ABI 3730 capillary sequencer
genepool.bio.ed.ac.uk/). Sequencing ambiguities were resolved manually using
CodonCode Aligner (http://www.codoncode.com).
type was estimated for all polymorphic sites (SNPs) within each marker, taking
into account the dominance relationships between different morphs. The
Amazonian form of H.numata termed silvana (widespread from French
Guiana to the Andean foothills) and its geographic replacement illustris
and illustris individuals are homozygous at P, whereas individuals of other, co-
occurring forms can be either heterozygous or homozygous for a different allele.
We estimated the association between genotype and phenotype by testing the
hypothesis that the major allele should be homozygous in silvana individuals
andheterozygous or absentin auroraindividuals. For eachpolymorphic site with
aminorallelefrequencyofatleast0.1, wecalculatedthe proportionofindividuals
phenotype–genotype association using Fisher’s exact test. This method allows
testing of the phenotype-by-genotype association while using knowledge of the
dominance relationships between P alleles.
Linkage disequilibrium (LD) across the P supergene. LD was assessed for all
pairs of polymorphic sites within and surrounding the P region, as well as in 12
unlinked markers (Fig. 2c) in 59 specimens from a polymorphic population near
based testing for LD with several alleles with unknown phase between sites37.
Significance was tested by a permutation test for the genotypic correlation statistic
Haplotype networks. The phase of SNP variation was determined by analysing
the segregation of alleles from parent to offspring in markers sequenced from the
mapping families, which originate from the same populations as the population
samples. Haplotypes from the population samples were inferred by coalescent-
networks were constructed by parsimony using the Network package39,40(http://
www.fluxus-engineering.com/). The level of genetic differentiation between the
silvanaand non-silvana groupswasestimated inDNAsp41using theFst statistics42,
and its significance was tested by permutation (Supplementary Fig. 5). Fst was not
used to test for genetic differentiation among different populations, but rather to
assess genetic differentiation between two groups of individuals in a single popu-
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