Phylogeography of Chilean Lizards: Histories of Genetic Diversification on the Western Slope of Southern Andes

Abstract

The western slope of the Southern Andes has complex orographic attributes and a dynamic paleoclimatic history, which seems to have been the driver of a great intraspecific genealogical diversification of lizards. Phylogeography tries to explain the spatial current patterns of genetic variation and genealogical intraspecific diversity, alluding to the features and the history of geographical scenarios. Although the number of these studies for South America is still low, the contributions that have emerged in recent years about the intraspecific diversification of reptiles in Chile have begun to sketch interesting hypotheses about the geographical factors that have likely contributed to the distribution of their genetic diversity. Such studies have focused mainly on species of the genus Liolaemus, the one with the highest levels of squamate species richness in southern South America. In West Austral Andes, a large part of the herpetofaunal diversity is concentrated in the Mediterranean and northern areas of the temperate forest, where several species are characterized by wide geographical ranges across varied environmental conditions. The general evidence indicates that the Chilean lizards have acquired high levels of genetic variability, coupled with complex geographic distributions and high levels of evolutionary differentiation, associated with landscape features, such as rivers and mountains. These influences have been further impacted by the interaction with dramatic past climate changes. Estimates based on mtDNA suggest that some of the species diversified during the Pleistocene (e.g., L. tenuis and L. pictus). These species have likely been most impacted by glaciations, suggested by a greater number of population reductions and postglacial expansions at greater latitude and altitude. These and other species, however, also show considerable levels of divergence and the existence of cryptic diversity (e.g., L. tenuis, L. pictus, and L. monticola). These patterns suggest that there may be more than one species within those that until now have been considered single taxonomic entities. It is also interesting to detect cases of congruent diversification among co-distributed lizards. From a biodiversity conservation perspective, the allopatric distribution of lineages of deep divergence and the spatial arrangements of genetic diversity and singularity suggest the existence of valuable intraspecific conservation units, most of which would be unprotected and in areas exposed to important anthropogenic changes.