Data from: Speciation with gene flow: evidence from a complex of alpine butterflies (Coenonympha, Satyridae)

Until complete reproductive isolation is achieved, the extent of
differentiation between two diverging lineages is the result of a dynamic
equilibrium between genetic isolation and mixing. This is especially true
for hybrid taxa, for which the degree of isolation in regard to their
parental species is decisive in their capacity to rise as a new and stable
entity. In this work, we explored the past and current patterns of
hybridization and divergence within a complex of closely related
butterflies in the genus Coenonympha in which two alpine species, C.
darwiniana and C. macromma, have been shown to result from hybridization
between the also alpine C. gardetta and the lowland C. arcania. By testing
alternative scenarios of divergence among species, we show that gene flow
has been uninterrupted throughout the speciation process, although leading
to different degrees of current genetic isolation between species in
contact zones depending on the pair considered. Nonetheless, at broader
geographic scale, analyses reveal a clear genetic differentiation between
hybrid lineages and their parental species, pointing out to an advanced
stage of the hybrid speciation process. Finally, the positive correlation
observed between ecological divergence and genetic isolation among these
butterflies suggests a potential role for ecological drivers during their
speciation processes.