The phylogeographic history of the threatened Diana fritillary, Speyeria diana (Lepidoptera: Nymphalidae): with implications for conservation

Abstract

The Diana fritillary, Speyeria diana (Cramer 1777) (Lepidoptera: Nymphalidae), is a North American endemic butterfly that disappeared from low elevation sites throughout its range in the twentieth century. It now persists in two geographically isolated mountainous regions, with an 800 km disjunction. Using mitochondrial cytochrome oxidase II DNA sequences from museum and field-sampled specimens, we found greater mtDNA diversity and more widespread differentiation among eastern populations than western ones. In addition, using coalescent-based population divergence models we dated the earliest splitting of eastern and western populations at least 20,000 years ago, during the Last Glacial Maximum. Therefore, the recent range collapse across the center of the historical species distribution may have exacerbated an ancient genetic differentiation between eastern and western populations. Finally, the loss of lowland haplotypes and the relatively large variation among local populations suggests that dispersal is low and lowland populations did not move to higher elevations, perhaps in response to climate change but, rather, appear to have vanished. Our results highlight the value of incorporating genetic data from preserved specimens when investigating the phylogeographic history and conservation status of a threatened species.