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I analyzed temporal variation in hybridization between the southwestern toad (Bufo microscaphus) and Woodhouse's toad (Bufo woodhousii) along the Virgin River in southwestern Utah and northwestern Arizona. Bufo woodhousii is largely restricted to the floodplain of the Virgin River from southern Nevada to the vicinity of St. George, Utah. By contrast, B. microscaphus is confined primarily to the tributaries of the Virgin River, only occupying the Virgin River proper exclusive of B. woodhousii along its upper reaches east of La Verkin Creek. As in all other zones of sympatry for these bufonids, behavior and morphology provide clear evidence of hybridization at a number of sites along the Virgin River. Analysis of...
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Declining amphibian populations in the arid southwestern United States have prompted increased efforts to understand the reproductive behavior of desert anurans, particularly those species in restricted habitats (Sullivan 1989, Corn 1994). The Arizona toad, Bufo microscaphus, is confined in southwestern Utah to tributaries of the Virgin River drainage (Price and Sullivan 1988). Like most desert anurans, B. microscaphus is an explosive breeder (Wells 1977, Sullivan 1992); however, unlike many other toads, which deposit their eggs in still ponds and lakes, it prefers to lay eggs in the flowing water of a perennial or semi-permanent stream. Water quality and breeding behavior are influenced by many physical and biological...
Hybridization between the southwestern toad (Bufo microscaphus) and Woodhouse's toad (B. woodhousii) along the Agua Fria and Hassayampa rivers in central Arizona was investigated over a 3-yr period. Variation in allozymes and the pulse rate of male release calls was compared with morphological variation in these taxa and their hybrids. At two sites on the Agua Fria drainage, data on release calls, but not morphology, were concordant with allozyme evidence of hybridization. At a third site on the Agua Fria, morphological data, but not release calls, corroborated electrophoretic evidence of hybridization. Along the Hassayampa River, all lines of evidence indicated that there has not yet been any hybridization in an...


    map background search result map search result map Egg mass deposition by Arizona toads, Bufo microscaphus, along a narrow canyon stream Egg mass deposition by Arizona toads, Bufo microscaphus, along a narrow canyon stream