Contrasting signatures of interspecific gene flow in the Atlantic Forest endemic butterfly Heliconius besckei
Year: 2026
Type: preprint
Abstract: Gene flow between diverging species can reshuffle genomic variation and greatly influence the speciation process, sometimes reinforcing, sometimes eroding species boundaries. However, the effect of ecological and historical processes on the patterns of introgression remains poorly understood. Here, we focus on the evolutionary history of Heliconius besckei , a geographically restricted butterfly endemic to the Brazilian Atlantic Forest, together with the mimetic H. melpomene nanna , the sympatric non-mimetic H. ethilla narcaea , and its closely related H. numata robigus . Using whole-genome sequencing, genome-wide tests of introgression, demographic modelling and palaeoclimatic species distribution models, we tested the extent and timing of interspecific gene flow in relation to mimicry, ecological context, and changes in geographic overlap. Despite strong genomic differentiation among the four focal Heliconius species, we detected widespread signatures of interspecific gene flow, greatly influenced by geographical overlap. Demographic models including post-divergence gene flow were better supported than strict-isolation models. In addition, genome-wide introgression analyses showed more numerous and larger candidate introgressed regions between H. besckei and H. ethilla narcaea , consistent with recurrent opportunities for exchange between these currently sympatric species. Species distribution models further recovered repeated expansions of suitable habitat for H. besckei during cold periods, providing a potential geographic context for secondary contact within the Atlantic Forest. Together, our results reveal recurrent gene flow occurring under different temporal, geographic, and potentially selective contexts, and show that the evolutionary history of a geographically restricted lineage can be shaped by repeated genetic exchange while substantial species differentiation is maintained.
Institutions: University of South Bohemia in České Budějovice, Institute of Entomology, Czech Academy of Sciences, Biology Centre, Centre National de la Recherche Scientifique, Laboratoire d'Écologie Alpine, Université Savoie Mont Blanc, Université Grenoble Alpes, University of Neuchâtel, Université de Montpellier, Centre d'Écologie Fonctionnelle et Évolutive, Lund University, Leibniz Institute for the Analysis of Biodiversity Change, Universidade Estadual de Campinas (UNICAMP)
Language: English
Subfield: Genetics
Domain: Life Sciences
SDG: Life on land
Open Access status: green
Funders: Jihočeská Univerzita v Českých Budějovicích, Fundação de Amparo à Pesquisa do Estado de São Paulo, Ministerstvo Školství, Mládeže a Tělovýchovy, Grantová Agentura České Republiky, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Instituto Chico Mendes de Conservação da Biodiversidade
OpenAlex ID: W7220865675