Genetic Structure and Population History of the Zaisan Toad-Headed Agama (Phrynocephalus melanurus) Inferred from Mitochondrial DNA COI Segments

The agamid lizard Phrynocephalus melanurus, is restricted to the Northwest China (Dzungar Basin) and adjacent Eastern Kazakhstan (Zaisan and Alakol basins). To elucidate the phylogeography of P. melanurus, we obtained the mitochondrial DNA COI segments of 175 sampled lizards from 44 localities across the whole distribution range. Phylogenetic analyses revealed two main clades comprising six geographically structured lineages (I, IIa, IIb, IIc1, IIc2, and IIc3) that fits an isola-tion by distance (IBD) model. The divergence from the most recent ancestor was dated to ~1.86 million years ago (Ma). Demographic analyses demonstrated lineage-specific response to past climate change: stable population for Clade I, IIb and IIc2; while past population expansion for IIc1 and IIc3 since 0.02 Ma and 0.18 Ma, respectively. Bayesian phylogeographic diffusion anal-yses detected initial spreading at the Saur Mount vicinity approximately 1.8 Ma. Historical species distribution modeling (SDM) projected expansion of the suitable habitat in the last interglacial period and stepwise contraction in the Last Glacial Maximum and Holocene epochs. The SDM predicts a shrinkage and shift of suitable area eastward as a response to future climate change. Our findings suggest that the evolution of P. melanurus followed a parapatric divergence with subsequent dispersal and adaptation to cold and dry environments during the Quaternary. Moreover, future conservation strategies need to be taken to maintain the population of lineage IIc1.