Browsing by Subject "Scaphiopus"
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Item Biochemical genetic investigations of introgressive hybridization and systematic relationships in the spadefoot toads, genus Scaphiopus(Texas Tech University, 1978-12) Sattler, Paul W.The primary purpose of this study is to more thoroughly document hybridization and possible introgression between the spadefoot toads (Scaphiopus bombifrons and S_. multiplicatus, using starch gel electrophoresis. Analysis of mating call recordings (Blair, 1955; Bogert, 1960) first suggested the possibility of hybridization between these species. This possibility was further investigated in northwestern Texas oy Forester (1973). On the basis of mating call analysis he classified 6.3% of the animals as natural hybrids and 10.9% as backcross progeny. The two forms have also been found to be compatible in experimental crosses. Interspecific crosses were 78-97% as successful as intraspecific crosses (Littlejohn, 1959; Wasserman, 1964; H. Brown, 1967; Forester, 1969). Forester (1969) found laboratory raised F, hybrid males to exhibit an average fertility of 61.9% as compared with controls.Item Community assembly of xeric-adapted anurans at multiple spatial scales(Texas A&M University, 2006-04-12) Dayton, Gage HartThe distribution and abundance of organisms is influenced by historical, abiotic, and biotic factors. The goal of my dissertation was to determine the distribution of anurans in the Big Bend region of the Chihuahuan Desert and to examine how abiotic and biotic factors shape the composition and structure of anuran communities at multiple spatial scales. My approach relied on extensive field surveys, laboratory and field experiments, and GIS modeling. Results from field surveys and reciprocal transplant studies of tadpoles indicate that abiotic conditions of the breeding site most likely do not play a significant role in causing the segregation of species among individual breeding pools. I used laboratory and mesocosm experiments to test for indirect and direct effects of predators on growth and survival of S. couchii tadpoles. I found that S. couchii tadpoles do not alter their behavior in the presence of predators and are very susceptible to predation. Although tadpoles reared with predators suffered high mortality rates, they metamorphosed significantly faster than tadpoles reared without predators. The reduced time to metamorphose is likely a result of the thinning of intraspecific competitors. Because the primary cause of death for S. couchii tadpoles is desiccation due to pond drying, predators may play an important role in facilitating metamorphosis by decreasing competitors and thus increasing per capita resources, therefore decreasing time to metamorphosis for the surviving tadpoles. At the landscape level anuran distributions seem to be influenced by environmental factors that influence the survival of the adult stage. At the level of the breeding site, microhabitat and abiotic components of the aquatic environment do not seem to play an important role in influencing breeding site use by different species. Rather, it seems likely that predation on tadpoles by predators is important in limiting the distribution of some species and that the fast-developing S. couchii may exclude other species from using sites via oophagy and predation on small tadpoles. My research elucidates the fact that in order to understand factors important in regulating ecological communities it is important to examine both abiotic and biotic factors at multiple spatial scales.Item Reproductive isolation and hybridization between the spadefoot toads Scaphiopus bombifrons and the Scaphiopus hammondi in West Texas(Texas Tech University, 1969-05) Forester, Donald CharlesNot available