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

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Abstract
Electrophoretic examination of the products [enzymes] of 29 gene loci in the 5 spp of Pholidobolus and 3 spp. of Proctoporus [Proctoporus sp., P. unicolor and P. hypostictus] 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 Pholidobolus affinis as the sister species to the other Pholidobolus, P. macbrydei as the sister species to the remaining taxa, and the 2 populations referred to P. prefrontalis as the sister species to P. montium plus P. 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; 3 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. With midpoint rooting, almost all phylogenetic informatin 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 changes) 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 phylogeny of the genus reveals that no contact zones of this parapatric complex involve 2 sister-species. This emphasizes the need for phylogenetic reconstruction as the 1st step in the examination of speciation mechanisms. This finding also suggests that competing species, rather than geographic barriers, may at time serve to isolate differentiating populations.