Keith B. Malmos

CALLING BEHAVIOR AND DIRECTIONAL HYBRIDIZATION BETWEEN TWO TOADS (BUFO MICROSCAPHUS X B. WOODHOUSII) IN ARIZONA

Abstract Male calling effort and mitochondrial DNA (mtDNA) variation were examined in a breeding chorus of toads from a hybrid zone between Bufo microscaphus and B. woodhousii in central Arizona. The chorus comprised 50 B. microscaphus and 17 hybrids, identified on the basis of morphology and advertisement calls; no pure B. woodhousii were observed. Males produced advertisement calls throughout the early evening, even when relatively large numbers of males (>50) were present at the chorus; active searching and satellite tactics were not observed. Calling efforts (call duration × call rate) of hybrids (23.9%, n = 8) and B. microscaphus (24.9%, n = 19) were similar and comparable to call efforts of B. woodhousii (21.9%, n = 10) from a different site. Moreover, repeatabilities of calling effort were significant (r = 0.45) for hybrid males, but not for B. microscaphus and B. woodhousii. Thus, calling behavior of hybrid males was neither significantly reduced nor more variable than that of their parental species. The distribution of mtDNA haplotypes revealed directional introgression is occurring between male B. microscaphus and female B. woodhousii: All 17 hybrids possessed B. woodhousii mtDNA. The proximate mechanism driving hybridization appears to involve common male (B. microscaphus) and rare female (B. woodhousii) matings as B. woodhousii expands its range.

Systematics of the Bufo woodhousii Complex (Anura: Bufonidae): Advertisement Call Variation

To determine whether Bufofowleri, Bufo woodhousii woodhousii, and Bufo woodhousii australis are diagnosable taxa, we examined variation in advertisement calls and body size across the range of the Bufo woodhousii complex. Calls were recorded and toads measured in six regions consisting of California, Arizona, Utah, Texas, Nebraska and Iowa, and New Jersey. Pulse rate and call duration, but not frequency, were significantly related to temperature. Dominant frequency was the only call variable of the three analyzed that correlated with snout-vent length. When adjusted for temperature and size effects, calls of B. fowleri had a shorter duration and higher dominant frequency than the other two members of the B. woodhousii complex. Discriminant analysis using call variables and body size provided clear separation of B. fowleri from B. w. woodhousii and B. w. australis. Univariate and multivariate analyses revealed that toads from southern California were most similar to toads from south-central Arizona currently recognized as B. w. australis. We conclude that B. fowleri should be recognized as a species. Continued recognition of B. w. australis and B. w. woodhousii as western forms of the B. woodhousii complex is reasonable.

Natural Hybridization among Distantly Related Toads (Bufo alvarius, Bufo cognatus, Bufo woodhousii) in Central Arizona

Putative hybrid toads of the genus Bufo were collected in central Arizona and identified using allozymes, qualitative and qalsntitative morphological characters, and release call characteristics. Data suggest one hybrid resulted from mating between Bufo cognatus and Bufo woodhousii, and the other three resulted from matings between Bufo alvarius and B. woodhousii. Natural hybridization between these taxa has not been previously reported. To date, B. woodhousii has been found to hybridize with four species of the Bufo americanus species group, of which B. woodhousii is a member, and five other species which represent three outgroups to the B. americanus group. Fossil evidence suggests some genomic compatability has been retained between B. alvarius and B. woodhousii despite at least 6 million years of independent evolution. Hybridization among members of Bufo may be due to alternative mating tactics of males, such as active searching, and by alteration of historical habitats in central Arizona. WT EATHIIN the Bufo americanus group of North

Mitochondrial Gene Markers for the Hybridizing Toads Bufo microscaphus and Bufo woodhousii in Arizona

Abstract Three restriction site markers from the mitochondrial genome are described for the toads Bufo microscaphus and B. woodhousii. Markers were resolved from DNA sequence data representing segments of cytochrome b (cytb) and 16S ribosomal genes. Two diagnostic restriction sites (BsmA I; SfaN I) characterize B. microscaphus for cytb, whereas a third restriction site (Tsp509 I) distinguishes B. woodhousii for 16S. Restriction digests of PCR-amplified cytb and 16S segments provide an economical, nondestructive assay with which to identify mtDNA haplotypes for these toads and their hybrids. The mtDNA markers complement diagnostic allozyme and call characters, offering an additional approach to examine hybridization between the two species in central Arizona.