APPARENT HYBRIDIZATION BETWEEN CNEMIDOPHORUS-GULARIS AND CNEMIDOPHORUS-SEPTEMVITTATUS FROM AN AREA OF SYMPATRY IN SOUTHWEST TEXAS

A potential area of sympatry for Cnemidophorus gularis and C. septemvi ttatus in Texas was identified from fine-mapping of museum locality re cords. The area was investigated and these tare taxa were found to occ ur together at a single locality. Variation in the phenotypes of speci mens observed and collected from this locality suggested hybridization between gularis and septemvittatus. Subsequent examination of several characters across the range for gularis and septemvittatus revealed c onsiderable inh aspecific variability in phenotypes. DNA sequences for 932 base pairs of the ND4 to tRNA(Leu) region of the mitochondrial ge nome were analyzed by a variety of phylogenetic and distance methods t o determine the relationship between gularis and septemvittatus collec ted at this locality and samples collected away from the area of sympa try. Data are also included for the outgroup taxa Teius teyou, Cnemido phorus inornatus, C. laredoensis, C. lemniscatus, C. sexlineatus, and C. tigris. Results from all analyses indicate extremely low levels of sequence divergence between gularis and septemvittatus relative to the divergence among the species of Cnemidophorus examined. The variation between the species gularis and septemvittatus is of a similar magnit ude to that found within the species tigris, inornatus, and sexlineatu s. Among the gularis collected in sympatry with septemvittatus, two ha ve DNA sequences which unambiguously place them within the septemvitta tus clade. The parthenoform C. laredoensis (female gularis x male sexl ineatus), (1) provides additional cladistic resolution within gularis, (2) is equidistant in divergence from gularis and septemvittatus and (3) is basal to both species. As both gularis and septemvittatus repre sent diagnosable taxa by both phenotypic and genetic data, we conclude that hybridization between gularis and septemvittatus in sympatry is the most likely explanation of the results.