Evolutionary Genetics of the Andean Lizard Genus Pholidobolus (Sauria: Gymnophthalmidae): Phylogeny, Biogeography, and a Comparison of Tree Construction Techniques

Abstract

Electrophoretic examination of the products of 29 gene loci in the five species of Pholidobolus and three species of Proctoporus largely substantiates the taxonomic arrangement that was based on earlier morphological work. The electrophoretic data are used to construct a phylogeny of the species and the morphological data are reanalyzed for comparison; these data sets are largely consistent. The hypothesized phylogeny places Ph. affinis as the sister species to the other Pholidobolus, Ph. macbrydei as the sister species to the remaining taxa, and the two populations referred to Ph. prefrontalis as the sister species to Ph. montium plus Ph. annectens. Because of the small size of the genus Pholidobolus and the concomitant small number of possible phylogenetic hypotheses, comparisons among various methods of constructing phylogenetic trees from electrophoretic data are facilitated. All 105 possible bifurcating unrooted trees were examined for each of 13 goodness-of-fit statistics; three similar trees were consistently favored by all criteria. If outgroup rooting is used, the most favored of these trees is identical to the most parsimonious cladogram. However, with midpoint rooting, almost all phylogenetic infor- mation is lost and the resulting tree is identical to the UPGMA phenogram. The midpoint- rooting option of distance trees reinvokes an assumption (equal rates of change) that the distance methods are supposed to avoid. This assumption is clearly not met for the genus Pholidobolus. Biogeographic analysis of the species of Pholidobolus with respect to the hypothesized phylog- eny of the genus reveals that no contact zones of this parapatric complex involve two sister species. This emphasizes the need for phylogenetic reconstruction as the first step in the ex- amination of speciation mechanisms. This finding also suggests that competing species, rather than geographic barriers, may at times serve to isolate differentiating populations. (Evolutionary genetics; phylogeny; biogeography; speciation; genetic distances; network rooting; Pholidobolus; Proctoporus.)