Gene flow and the genealogical history of Heliconius heurippa

Camilo Salazar,Marcus R Kronforst,Mauricio Linares,Chris D Jiggins,Jesse E Taylor

doi:10.1186/1471-2148-8-132

Abstract

BackgroundThe neotropical butterfly Heliconius heurippa has a hybrid colour pattern, which also contributes to reproductive isolation, making it a likely example of hybrid speciation. Here we used phylogenetic and coalescent-based analyses of multilocus sequence data to investigate the origin of H. heurippa.ResultsWe sequenced a mitochondrial region (CoI and CoII), a sex-linked locus (Tpi) and two autosomal loci (w and sd) from H. heurippa and the putative parental species, H. cydno and H. melpomene. These were analysed in combination with data from two previously sequenced autosomal loci, Dll and Inv. H. heurippa was monophyletic at mtDNA and Tpi, but showed a shared distribution of alleles derived from both parental lineages at all four autosomal loci. Estimates of genetic differentiation showed that H. heurippa is closer to H. cydno at mtDNA and three autosomal loci, intermediate at Tpi, and closer to H. melpomene at Dll. Using coalescent simulations with the Isolation-Migration model (IM), we attempted to establish the incidence of gene flow in the origin of H. heurippa. This analysis suggested that ongoing introgression is frequent between all three species and variable in extent between loci.ConclusionIntrogression, which is a necessary precursor of hybrid speciation, seems to have also blurred the coalescent history of these species. The origin of Heliconius heurippa may have been restricted to introgression of few colour pattern genes from H. melpomene into the H. cydno genome, with little evidence of genomic mosaicism.

Highlights

The neotropical butterfly Heliconius heurippa has a hybrid colour pattern, which contributes to reproductive isolation, making it a likely example of hybrid speciation
Genealogical pattern and introgression Heliconius heurippa was initially identified as a putative hybrid species based on its intermediate colour pattern, which shows a striking similarity to phenotypes produced after just a few generations of hybridization between H. c. cordula and H. m. melpomene [26]
All four autosomal loci showed a pattern in which H. heurippa shares similar alleles with both H. m. melpomene and H. c. cordula

Summary

Introduction

The neotropical butterfly Heliconius heurippa has a hybrid colour pattern, which contributes to reproductive isolation, making it a likely example of hybrid speciation. 'magic traits' sensu Gavrilets 2004 [16]), hybridization could make a direct contribution to reproductive isolation of a novel lineage and to speciation [5,17]. Under this scenario, if establishment of the hybrid trait involved many generations of backcrossing, the genome of the novel hybrid linage could be predominantly derived from one of the parental species [17]. Heliconius pattern diversity could be facilitated by the movement of pre-established colour pattern adaptations [20,22,23]

Methods

Results

Discussion

Conclusion