Thesis (M.S.)--Rutgers University, 2010. / "Graduate Program in Ecology and Evolution." Includes bibliographical references (p. 55-57).

No description available.

I examined oviposition in four pond-breeding amphibians (northwestern salamander [Ambystoma gracile], long-toed salamander [Ambystoma macrodactylum], Pacific treefrog [Hyla regilla], northern red-legged frog [Rana aurora aurora]), at Burlington Bottoms, a lowland riverine site in northwestern Oregon, to determine whether differential use of native versus exotic plant substrates occurs. I found differential use in all four species, but use was inconsistent with the hypothesis that selection for native plants (or selection against exotic plants) was occurring. If selection was occurring, the pattern implied that reed canarygrass (Phalaris arundinacea), a widespread exotic in this lowland system, was sometimes favored. However, inconsistent use of reed canarygrass led me to examine the alternative that substrate strength (measured as density, diameter, and mass), rather than plant status, might be the basis of selection. Species used for oviposition differed in strength, but eggs were not consistently laid on braces based on my strength measures. Failure to find support for this hypothesis led to examination of a third hypothesis for two species (red-legged frog and northwestern salamander), that cover characteristics of the oviposition brace or nearby vegetation might influence egg mass location. Analysis of structural complexity of species used as a brace (as percent cover within 15 em of the egg mass) did reveal a pattern consistent with complexity, but that was species-specific. Red-legged frogs selected braces with significantly more nearspace cover; northwestern salamanders selected braces with sparser cover. Comparison of marginal shrub and tree cover to the number of red-legged frog egg masses revealed that ponds with < 50% shrub/tree cover had few (< 5) masses. Ponds with ≥ 50% shrub/tree cover had many (≥ 10) masses. More complex vegetation may provide greater protection for egg masses or ovipositing red-legged frogs but further investigation is clearly warranted. Elucidating northwestern salamander cover requirements will require examining more occupied ponds. In particular, more refined examination, using experimental manipulation, is needed to verify the cover relationships revealed in this study. Meanwhile, managers should treat cover as important in red-legged frog oviposition life history, paying special attention to minimizing loss of marginal shrub and tree cover.

This study assessed the influence of landscape development on stream-associated amphibians in forested riparian areas within the Portland-Vancouver metropolitan region. Human alteration of landscapes may dramatically affect the ecology of neighboring aquatic systems. It was hypothesized that lotic amphibians would be negatively associated with greater amounts of landscape development and positively associated with forested area within the surrounding watershed. Thirty-seven 1st-3rd order streams were sampled between June 21st and September 21st in 2011. Streams potentially providing adequate habitat for stream-obligate amphibians were randomly selected. Amphibians were surveyed along 30-meter stream transects using an active-cover search (ACS). Environmental variables associated with development in surrounding landscapes were measured in situ. GIS delineation was conducted to define landscape-scale variables at stratified distances from riparian networks up-stream of each site via the utilization of the 2006 NLCD dataset and a finer-scale, regional dataset compiled by the Institute for Natural Resources (INR). Amphibians were detected at seventeen of the thirty-seven sampled streams. The most commonly detected species were Dicamptadon tenebrosus, Plethadon vehiculum and Plethadon dunni. Streams where amphibians were observed had lower average water temperature and conductivity, coarser stream substrate and were located on public property more often than streams where no amphibians were detected. Landscape variables were most significant to amphibians within 100 and 200 meters of the upstream stream network. Occupancy of a site by facultative species was best explained by the proportion of mixed forest in the surrounding watershed (R2=0.343, p<0.001). Occupancy of a stream by obligate species was best predicted by measurements of water quality and in-stream cover (Water Temperature: R2=0.275, p<0.001; Water Conductivity: R2=0.248, p<0.001; Cover: R2=0.323, p<0.001). Occupancy of stream refugia by all observed amphibians was positively influenced by higher percentages of forest cover and lower percentages of urban development and herbaceous vegetation in the surrounding watershed. Results of this study indicate that urban refugia must contain adequate riparian forest area, coarse stream substrate and clean, cool water to sustain stream-amphibian communities. Protection of remnant forested headwater stream networks is essential to the conservation of lotic amphibians in this urbanized region.

The purpose of the present study of the herpetofauna was to obtain additional information regarding the vertebrates of Denton County, and to produce a well-preserved, cataloged collection of the amphibians and reptiles for the Museum of Zoology, North Texas State University. An understanding of the vertebrate life of the county also involves an investigation of the habitats within the county that may, in part, count for the distribution of these animals. It is well recognized that the environmental areas of the county have altered vastly during the last one hundred years. This alteration is due largely to agriculture and industry. However, there are adequate numbers of natural environments, as well as newly created ones that may contribute to the distribution of the vertebrates at the present time. Therefore, the problem not only concerned the collection of specimens, but also the identification, abundance classification, general habitat classifications, and county distribution.