Amat Orriols, F. & D. Escoriza

Molecular biogeography and niche climatic diversification of sand lizards (Lacerta agilis) with special emphasis on the history of the Pyrenean populations. pp. 284-296 plus Supplementary material.

Abstract. Pleistocene climate oscillations had a dramatic impact on the distribution of temperate ectothermic organisms. These range fluctuations plausibly have left a footprint on the species’ genetic structure which is linked with modelled paleo­climatic conditions, allowing us to infer which environmental factors shaped the evolutionary history of Sand lizards. In this study, we evaluated the patterns of niche diversification of Lacerta agilis in Eurasia, based on mitochondrial DNA analyses and ecological niche models. The lineage of Sand lizards evolved 3.8–1.8 Mya, being the most basal in the east-Caucasian subclade, with eight mitochondrial subclades separated into two groups. These groups represent two independent waves of expansion from the ancestral region constituted by the Caucasus and the adjacent northern plains to the Paleartic. Paleoclimatic models suggested a high instability of the range of this lineage in the last 3 Mya, with niche contractions during the colder glacial periods and expansions following the glacier retreat. This suggested an allopatric diversification process, with subspecies boundaries upon secondary contact maintained by competitive interactions, at least between closely related pairs. The great mountain systems of the Mediterranean Peninsulas constituted stable refugia during the Pliocene–Pleistocene cycles, favouring the evolution of endemic subclades. These montane subclades have higher mitochondrial diversity than those that occur in the plains. However, the Pyrenean endemic L. agilis garzoni is exception possibly due to the occupation of a very small refugium during the recent glacial phases.

Key words. Glacial oscillations, Lacertidae, niche conservatism, paleoclimate, phylogeography.