Genetic and phenotypic variation in wood tiger moths from the Caucasus: insights into male warning color variation

Coloration plays a pivotal role in shaping how species adapt to their environment, influencing their interactions with predators, prey, and potential mates. The aposematic wood tiger moth (Arctia plantaginis) is sexually dimorphic. Males are polymorphic in their hindwing coloration across the Holarctic distribution range, while females exhibit continuous variation in their coloration. In the Caucasus region, a striking exception can be found, where both sexes exhibit a continuous orange-red hindwing coloration. Yet, it remains uncertain whether significant color variations exist within the spectrum of male orange-red coloration and whether these differences can be associated with genetic structure or other phenotypic traits such as size. Using population genetics and image analyses methods, we find that males from the Lesser Caucasus have predominantly large red wings and constitute mostly a single genetic population. Males from the Greater Caucasus, in contrast, appear genetically isolated and are relatively small with orange hindwings. We discuss these findings in the context of both contemporary and historical environmental factors that may have influenced male color variation in the region.