PHYLOGENETIC RELATIONSHIPS AND MOLECULAR VARIABILITY WITHIN AND AMONG SIX CHROMOSOME RACES OF SCELOPORUS GRAMMICUS (SAURIA,IGUANIDAE), BASED ON NUCLEAR AND MITOCHONDRIAL MARKERS

Selected populations of Sceloporus grammicus from central Mexico were karyotyped and screened for variability at the protein, ribosomal-DNA, and mitochondrial-DNA levels. Molecular markers were used to construct phylogenies of the chromosome races, which were then qualitatively evaluated for congruence with each other and with the original chromosomal phytogeny proposed by Hall (1973). Between-cytotype protein divergence generally was low, and few allozyme markers were fixed between cytotypes. Hence, these data were combined with the rDNA restriction-site data for phylogeny reconstruction. This combined nuclear data set provided a phylogenetic hypothesis that, with one exception, is reasonably congruent with that based on standard karyotypes. Similar results were obtained from mtDNA restriction-site data, although there are some discrepancies, and trees based on both DNA data sets are complicated by evidence for historical and/or ongoing hybridization. An unexpectedly rapid rate of rDNA divergence is demonstrated relative to the degree of allozyme divergence, suggesting that restriction-site variation in rDNA has systematic utility at lower taxonomic levels.