Meeting Abstract
Identifying the forces responsible for driving genomic divergence between incipient species remains a challenging but central area of research in evolutionary biology. Such forces can include divergent natural selection, but also the historical demography of interacting populations. Population size changes and variable migration rates can lead to the accumulation of heterogeneous genomic differences between populations despite the absence of selection. Thus, a major goal in speciation genomics research is to disentangle these forces by modeling the demographic history. Populations of the neotropical butterfly genus Heliconius provide an ideal system to study the effects of population demography during divergence. Heliconius himera is considered an incipient species within the Heliconius erato clade that displays increased genome-wide levels of divergence with neighboring H. erato populations. Here, we use diffusion simulations to model the demographic scenarios that could potentially impact patterns of genomic divergence between hybridizing incipient species H. erato and H. himera. Demographic modeling shows that both species experienced bottlenecks in their recent histories, followed by limited expansion in H. himera and much larger expansion on H. erato. Models of species divergence supported a period of isolation between the species, followed by secondary contact with H. erato populations west of the Andes. Further analysis showed there was an excess of introgression from H. erato in the H. himera population. These results highlight the importance of demographic history in shaping heterogeneous patterns of genomic divergence between hybridizing species.
