Phrynocephalus

Abstract: Phrynocephalus vlangalii is restricted to dry sand or Gobi desert highlands between major mountain ranges in the Qinghai (Tibetan) Plateau. Mitochondrial DNA (mtDNA) sequence (partial ND2, tRNA(Trp) and partial tRNA(Ala)) was obtained from 293 Phrynocephalus sampled from 34 sites across the plateau. Partitioned Bayesian and maximum parsimony phylogenetic analyses revealed that P. vlangalii and two other proposed species (P. erythrus and P. putjatia) together form a monophyletic mtDNA clade which, in contrast with previous studies, does not include P. theobaldi and P. zetangensis. The main P. vlangalli clade comprises seven well-supported lineages that correspond to distinct geographical areas with little or no overlap, and share a most recent common ancestor at 5.06 +/- 0.68 million years ago (mya). This is much older than intraspecific lineages in other Tibetan animal groups. Analyses of molecular variance indicated that most of the observed genetic variation occurred among populations/regions implying long-term interruption of maternal gene flow. A combined approach based on tests of population expansion, estimation of node dates, and significance tests on clade areas indicated that phylogeographical structuring has been primarily shaped by three main periods of plateau uplift during the Pliocene and Pleistocene, specifically 3.4 mya, 2.5 mya and 1.7 mya. These periods corresponded to the appearance of several mountain ranges that formed physical barriers between lineages. Populations from the Qaidam Basin are shown to have undergone major demographic and range expansions in the early Pleistocene, consistent with colonization of areas previously covered by the huge Qaidam palaeolake, which desiccated at this time. The study represents one of the most detailed phylogeographical analyses of the Qinghai Plateau to date and shows how geological events have shaped current patterns of diversity.

Abstract: Determining the susceptibility of species to changing thermal niches is a major goal for biologists. In this paper we develop an eco-physiological model of extinction risk under climate change premised on behavioral thermoregulation. Our method downscales operative environmental temperatures, which restrict hours of activity of lizards, hr , for present-day climate (1975) and future climate scenarios (2070). We apply our model using occurrence records of 20 Phrynocephalus lizards (or taxa in species complexes) drawn from literature and museum records. Our analysis is phylogenetically informed, because some clades may be more sensitive to rising temperatures. The limits for computed hr predict local extirpations among Phrynocephalus lizards at continental scales and delineate upper boundaries of thermal niches as defined by Extreme Value Distributions. Under the 8.5 Representative Concentration Pathway scenario, we predict extirpation of 64% of local populations by 2070 across 20 Phrynocephalus species, and 12 are at high risk of total extinction due to thermal limits being exceeded. In tandem with global strategies of lower CO2 emissions, we propose regional strategies for establishing new national parks to protect extinction-prone taxa by preserving high-elevation climate refugia within existing sites of species occurrence. We propose that evolved acclimatization - maternal plasticity - may ameliorate risk, but is poorly studied. Previous studies revealed that adaptive maternal plasticity by thermoregulating gravid females alter progeny thermal preferences by ±1 °C. We describe plasticity studies for extinction-prone species that could assess whether they might be buffered from climate warming - a self-rescue. We discuss an epigenetic framework for studying such maternal-effect evolution.