Abstract
The Apollo butterfly, Parnassius glacialis, is one of the most charming members of its genus and includes two subspecies locally distributed in montane areas of south-central China and Japan. In this study, we investigated the genetic structure and demographic history of P. glacialis by analyzing partial sequences of four mitochondrial genes and nuclear single nucleotide polymorphisms (SNPs) via genotyping-by-sequencing (GBS) of samples from nearly the entire known distributional range in China. The mitochondrial DNA (mtDNA) data demonstrated that a total of 39 haplotypes were present, and the species was estimated to have diverged about 0.95 million years ago during the middle Pleistocene transition into two main clades that likely formed during the Kunlun-Huanghe tectonic movement. The two clades then dispersed independently in distinct geographic areas alongside the mountainous routes in central and southern China, most likely driven by the Pleistocene glacial-interglacial cycles. Nuclear SNP analysis was generally congruent with mtDNA results at the individual level. A minor incongruence of genetic structures that was detected between mtDNA and nuclear SNP data from the Laojunshan and Tiantangzhai populations was likely due to secondary contact and male-biased dispersal. Our work demonstrates that complicated dispersal-vicariance evolutionary processes likely led to the current geographic distribution of P. glacialis in China, particularly the uplift of the Qinghai-Tibet Plateau and related climatic oscillations during the Quaternary period.