Comparative analysis of the distribution and habitats of two Eremias species (Reptilia, Lacertidae) using niche-based GIS modeling

Abstract

The distribution and habitat characteristics of two Eremias species ( E. arguta and E. stummeri ) from contiguous areas of southeastern Kazakhstan, northeastern Kyrgyzstan, and western Xinjiang, China, were analyzed using GIS modeling. We show that both species are dry-steppe-adapted xerophilous lizards with sclerophilic and partially petrophilic specialization. In spite of the visible similarity of the ecological niches (ENs) occupied by E. arguta and E. stummeri , the latter differs in a number of key variables. While most of the precipitation variables, the radiation of the winter and off-season months, and afternoon (PM) humidity are most important for E. arguta habitats, the habitats suitable for E. stummeri are limited by temperature variables, radiation during most of the year, and morning (AM) humidity. Differences on this scale indicate the way in which these lizards are adapted to different ecosystems — E. arguta to the plains and E. stummeri to the mountains — and support the views on their different zoogeographical accessory. A visible correspondence of the distributional pattern of the two Eremias species to the mountain piedmonts and low foothills, with Pliocene-Quaternary concreted pebble deposits and the loess strata, permit us to consider mountain trails as the most likely means by which the species expanded in the Late Cenozoic period. Pronounced isolation of the populations in the Northern and the Central Tien Shan intra-montane depressions appears as a factor from at least the Late Pliocene ( E. stummeri ) and the Middle Pleistocene ( E. arguta ) periods; and the association of the lizard habitats with loess deposits has given rise to the suggestion that there was an absence of serious change in their ranges during the Last Glacial Maximum (LGM). Low precipitation, a high annual temperature range and the high aridity of the climate in general beyond the ENM optimum of E. arguta all point to severe conditions for lizards surviving already in the eastern part of the Ily Basin and explain the limited species distribution in the highly arid deserts of Xinjiang. In terms of methodology, our data highlights the lack of a ‘generalized set’ of BIOCLIM parameters in the ecological niche modeling of the mountain species. In particular, moisture and solar radiation as well as the relief variables play an important role in the ecological health of the poikilothermic xerophilous species inhabiting mountain areas.