Adaptive radiation of Batesian mimetic butterflies across a tropical archipelago

Most examples of adaptive radiation involve interspecific variability in morphology related to feeding—either consuming different items or feeding in different microhabitats.  We characterize a novel form of adaptive radiation in which butterfly lineages evolve radically different wing patterns and colors to mimic different unpalatable models on the islands of a tropical archipelago. The satyrine genus Elymnias comprises ca. 50 Asian and 1 African species. All but a few species are Batesian mimics of highly varied, unpalatable butterflies, and many species are sexually dimorphic mimics, with males and females mimicking strikingly different models or sexually dimorphic models.  We reconstruct the evolutionary history of this genus using 6 genetic markers, estimate the timing of diversification, then infer the group’s biogeographic history across the Indo-Australian Archipelago (IAA), where there are many island endemics.  We find that similar wing patterns occur in non-sister taxa, apparently because different lineages convergently evolve resemblance to the same, widespread model species in different areas.  Sexually dimorphic mimicry is a highly labile trait and appears to have evolved repeatedly in the group.  Sister taxa only co-occur on large islands.  The Asian lineage appears to be ca. 2 my old, with many species dating to the last glacial maximum around 20 kya when changes in sea level altered the connectivity of insular landmasses in the IAA.  This suggests that the dynamic and varied insular geography of the IAA set the stage for allopatric diversification, followed by local morphological adaptation to resemble locally available, unpalatable model species.