 2001 by the American Society of Ichthyologists and Herpetologists Copeia, 2001(3), pp. 775–780 Mitochondrial Phylogeny of Namib Day Geckos (Rhoptropus) Based on Cytochrome b and 16S rRNA Sequences TRIP LAMB AND AARON M. BAUER We examined phylogenetic relationships among the Namib day geckos (genus Rhoptropus) using DNA sequence data from the mitochondrial cytochrome b (cytb) and 16S ribosomal RNA genes. Maximum-parsimony analysis of the cytb, 16S, and combined (cytb/16S) datasets each recovered an identical single most-parsimonious tree, revealing two well-supported clades: (1) Rhoptropus afer  Rhoptropus bradfieldi ssp and (2) Rhoptropus boultoni  (Rhoptropus barnardi  Rhoptropus biporosus). Max- imum-likelihood analysis identified the same two species groups and corroborated patterns of relationship within respective parsimony clades. Moreover, the mito- chondrial DNA trees were congruent with parsimony trees derived from morpho- logical and allozymic characters. Congruence observed among these different data offers strong evidence for our molecular phylogeny of Rhoptropus, bringing taxo- nomic stability to a genus whose species-level relationships were widely debated throughout the last century. T HE Namib day geckos (genus Rhoptropus) form an unusual assemblage of strictly di- urnal gekkonines endemic to the arid regions of western Namibia and southern Angola. In ad- dition to diurnal activity, Rhoptropus exhibits sev- eral apomorphic features that are otherwise rare or unique among gekkonine geckos. These diagnostic characters include the following: (1) a reduced number of presacral vertebrae (24– 25 vs 26 in other African gekkonines); (2) ven- trolateral fat deposits; and (3) a ligamentous binding between the metatarsals of digits II and III, which causes these elements to lie parallel (Bauer and Good, 1996). Conversely, other dig- ital features, most notably the hyperphalangy of digit I, reflect close evolutionary ties of the ge- nus to the Pachydactylus group, a large assem- blage of Afro-Mediterranean gekkonines (Rus- sell, 1972; Haacke, 1976; Kluge and Nussbaum, 1995). We recently generated molecular phylo- genetic support from mitochondrial sequence data for this systematic interpretation, identify- ing Rhoptropus as the sister taxon to Pachydactylus sensu lato (unpubl.). Intrageneric relationships among the Namib day geckos have been less tractable. Centered largely in the mid-1900s, the systematic history of Rhoptropus entailed extensive debate over spe- cies boundaries, resulting in taxonomic flux and frequent nomenclatural misapplication. By the time the last of six currently recognized spe- cies was described (Laurent, 1964), each taxon (except Rhoptropus afer) had been linked to ev- ery other taxon through misidentification, syn- onomy, or presumed affinity (for a review, see Bauer and Good, 1996). Russell (1972) ad- dressed scalation features in a preliminary as- sessment of relationships within Rhoptropus. Bauer and Good (1996) provided a more defin- itive phylogenetic hypothesis in a cladistic anal- ysis of 16 morphological and six allozymic char- acters (Fig. 1). Herein, we present a phyloge- netic analysis of sequence data from the mito- chondrial cytochrome b and 16S ribosomal RNA genes. We compare the phylogenetic estimates from these different datasets to assess levels of congruence, from which we infer a Rhoptropus phylogeny. MATERIALS AND METHODS Liver tissue was obtained for five of the six species of Rhoptropus (samples of the Angolan endemic Rhoptropus taeniostictus could not be se- cured). We processed 2–3 specimens per spe- cies, choosing localities that maximized distance between collection sites to assess levels of intra- specific variation. Two of the six species, Rhop- tropus boultoni and Rhoptropus bradfieldi, are poly- typic. We secured both subspecies of R. bradfieldi (Rhoptropus bradfieldi bradfieldi, Rhoptropus brad- fieldi diporus) but caught only the nominate sub- species for R. boultoni. The remaining subspe- cies Rhoptropus bradfieldi benguellensis and Rhop- tropus bradfieldi montanus, both Angolan endem- ics, were not accessible. Two basal species within the sister taxon Pachydactylus (Pachydactylus bi- bronii and Pachydactylus tetensis) were selected as outgroups. Tissue samples were processed at field collec- tion sites and preserved in liquid nitrogen (for subsequent storage at -80 C) or in a saturated salt-DMSO buffer (Amos and Hoelzel, 1991). Genomic DNA was extracted from liver using