 2004 by the American Society of Ichthyologists and Herpetologists Copeia, 2004(4), pp. 758–769 Geographic Variation in Hyla wrightorum: Advertisement Calls, Allozymes, mtDNA, and Morphology ERIK W. A. GERGUS,TOD W. REEDER, AND BRIAN K. SULLIVAN We studied geographic variation in allozymes (22 loci), mitochondrial cytochrome b gene sequences (575 bp), advertisement calls (pulse rate, call duration, and dom- inant frequency), and snout–vent length among populations of Hyla wrightorum and Hyla eximia in the United States and Mexico. Calls were only available for H. wrigh- torum, and although populations varied in some advertisement call variables, there was no indication of species level differentiation. Allozyme variation was exhibited among the H. wrightorum populations, but no fixed differences were discovered, and the amount of genetic divergence among populations was small (D m  0.0643). Seven mtDNA haplotypes were discovered among the H. wrightorum individuals in- cluded in this study. A single haplotype (G) was present in the Huachuca Mountains and was found only in this population restricted to southeast Arizona. Neither the Mogollon Rim nor the Sonora populations were exclusive, with some haplotypes in each being more closely related to haplotypes in the other population. Molecular data (allozymes and mtDNA), as well as the advertisement calls, support continued recognition of two species: H. eximia in central-southern Mexico and H. wrightorum, which consists of disjunct populations in the Sierra Madre Occidental of northern Mexico, the Huachuca Mountains of southeastern Arizona, and the mountains of central Arizona and western New Mexico. T HE Arizona Treefrog, Hyla wrightorum, has received little attention (Renaud, 1977; Sullivan, 1986) and, until recently, was often synonymized under Hyla eximia (Duellman, 2001). Hyla eximia was described by Baird (1854) with a type locality from ‘‘Valley of Mex- ico’’ (Districto Federal), Mexico, and it occurs throughout the southern parts of the Mexican Plateau (= Mesa Central), the Sierra Madre Oriental and Sierra Madre Occidental, and the Cordillera Volca ´nica in central Mexico (Duell- man, 2001). Hyla wrightorum was diagnosed by Taylor (1938) as a species separate from H. ex- imia based on the presence in the former of larger size, anterior edge of tibia with heavy brown spots and lacking a white line, and pro- portionately longer legs. Populations of H. wrightorum occur along the Mogollon Rim of central Arizona into western New Mexico, the Huachuca Mountains and adjacent Canelo Hills of southeastern Arizona, and the northern Si- erra Madre Occidental of Mexico. Following Taylor’s (1938) description, Schmidt (1953) arbitrarily listed H. wrightorum as a subspecies of H. eximia. Shortly thereafter, Blair (1960) provided evidence from mating calls indicating subspecies designation was pre- mature; he described ‘‘Fast eximia’’ and ‘‘Slow eximia’’ populations whose pulse rates of adver- tisement calls at similar recording temperatures were dramatically different between southern Mexico and Arizona, and suggested the exis- tence of two species. Jameson et al. (1966) rec- ognized H. wrightorum as a subspecies of Pseu- dacris regilla based on a multivariate discrimi- nant function analysis of 10 morphological mea- surements. Maxson and Wilson (1974) compared serum albumins of H. eximia, P. regil- la, and H. wrightorum and argued that H. eximia and H. wrightorum are closely related but rela- tively divergent from P. regilla, contrary to Ja- meson et al. (1966). Renaud (1977) subsequent- ly compared morphometric, allozyme, and ad- vertisement call variation of Mogollon Rim and mainland Mexico populations and concluded that Arizona H. wrightorum could be distin- guished from H. eximia of southern Mexico based on differences in size (snout–vent length, or SVL), shape, and dominant frequency of male advertisement calls. Renaud (1977) did not find a statistically sig- nificant relationship between advertisement call dominant frequency (DF) and pulse rate (PR) against wet and dry-bulb air temperatures, water temperature, or SVL; hence no correction fac- tors were applied in analyses of call data. How- ever, Sullivan (1986) found a significant differ- ence in mean pulse rate of treefrogs he record- ed at Baker Lake, Arizona, leading him to con- clude that pulse rate may be influenced by body temperature, contrary to Renaud’s (1977) asser- tion. Additionally, Sullivan (1986) found a sta- tistically significant relationship between DF and SVL, contrary to Renaud (1977). Regard-