Abstract
Initiation of breeding activity of Bufo houstonensis followed a rise in minimum air temperature in January or February to above approximately 14?C. Rain was not a direct necessary stimulus to breeding in this species; additional site-specific stimuli apparently are necessary; rapid algal growth may be such a stimulus. Amplectant male B. houstonensis were significantly larger than non-amplectant males. Based on growth data from recaptured males, it is likely that older male B. houstonensis are more likely to achieve amplexus than are first-season males. Data on breeding behavior and movements to and from breeding sites are presented. Natural hybrids between B. houstonensis and B. woodhousei and between B. houstonensis and B. valliceps were identified morphologically and electrophoretically. Only one suspected backcross product was found. Hybridization among these species was minimal in the study areas - in all cases less than 1% of the parental populations. The primary isolating mechanisms are temporally offset breeding seasons (of B. houstonensis and B. valliceps) and habitat isolation (B. houstonensis and B. woodhousel). The population sizes of B. houstonensis in Bastrop Co., Texas, are larger than previously reported; present population sizes in this area appear not to be critically low. The restricted range of the species coupled with habitat destruction seem to be the primary factors in the endangerment of B. houstonensis.
Published Version
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