Browsing by Subject "Amphibians"
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Item A cytological study of parthenogenetically activated eggs of Rana pipiens(Texas Tech University, 1966-08) Ramirez, Samuel AmadorNot availableItem AMPHIBIANS OF THE SOUTHERN GREAT PLAINS: HABITAT AND THE IMPACTS OF TEMPERATURE AND pH ON SURVIVAL(2013-05) Kissner, Jessica; Griffis-Kyle, Kerry; McIntyre, Nancy E.; Haukos, David A.; Wallace, Mark C.Global climate change has had an increasing role in the decline of amphibian populations due to direct (e.g. critical temperature thresholds) and indirect (e.g. temperature stress, spreading of disease, and habitat alteration and loss) effects of increasing atmospheric temperature. Due to the complexity of habitats needed to complete all of their life stages, amphibians are subject to stressors through a number of systems (e.g., water quality, climatic characteristics, and terrestrial habitat). Furthermore, habitat currently used by amphibians may become inhospitable due to indirect stressing effects of increased temperatures projected for the Southern Great Plains (SGP). To protect and manage for species at risk, we must first understand their basic community assemblages, distributions, habitat associations, and tolerances. Because little amphibian research has come from northeastern New Mexico, collecting data on these parameters will be a useful tool for future research and management in this area. The objectives of this study were to: (1) examine amphibian species presence, richness, an index of reproductive success, and larval growth in northeastern New Mexico and relate them to site-specific and landscape-level habitat characteristics and (2) identify environmental factors that may jeopardize population persistence in the future. After conducting field work, I determined an additional objective based on the current average high temperature (28.3°C) and pH ranges (4.9 to 9.4) I recorded: (3) to determine the effect of a 5.6°C increase in average summer temperature by 2090 (to 33.9°C) due to climate change on embryo and tadpole survival, the effects of pH 4.9 and 9.4 on embryo and tadpole survival, and the effects of the interactions between pH and temperature on embryo and tadpole survival. Over 2011 and 2012, I sampled each playa wetland 5 times over a 17-day sampling period after precipitation of >2cm using call, visual encounter, egg mass, dip net, and funnel trap surveys to examine the amphibian community. I also collected tadpole measurements throughout development to examine larval growth patterns. Water quality was sampled during each survey, and ArcMap was employed to determine landscape-level habitat features. I sampled 14 playa wetlands in northeastern New Mexico, detecting 7 amphibian species with a maximum species richness per playa of 4. I detected reproduction in 4-6 species (as Pelobatid tadpoles are difficult to identify to species), and larval growth in Anaxyrus cognatus, Pseudacris clarkii, and Pelobatid spp. was exponential up to age 17 days (all p < 0.01). I also documented the first New Mexico state record of Pseudacris clarkii (spotted chorus frog). Although I did not document any statistically significant associations between amphibian species presence, richness, or reproductive success and habitat characteristics, I observed a trend of no P. clarkii reproduction at the acidic sites (4.9-6.9) even though adults were present in playa wetlands with pH 4.9-9.4. Based on my field observations about amphibian natural history from 2011, I hypothesized that increased temperature due to global climate change in 2090 may influence the ability of anurans to survive in pH-stressed playas. I tested these hypotheses in the lab in order to strengthen my field-based inferences. In 2012, I performed a fully-factorial laboratory experiment using the 2011 pH extremes (4.9 and 9.4), 2011 current average temperature (28.3°C), and 2090 projected temperature (33.9°C ), with embryos from 3 pairs of wild-caught P. clarkii. The results of my experiment suggest that P. clarkii cannot successfully reproduce in water with high temperature (33.9°C), regardless of the pH conditions. Furthermore, survival to metamorphosis in acidic conditions (pH 4.9), regardless of temperature, is unlikely, findings consistent with both my field observations and laboratory results. Survival to metamorphosis in basic conditions (pH 9.4) is very low (9%), compared to survival at pH 7 (84 %) that other studies have documented. Based on my findings, an increase in summer temperature of 5.6°C over the next 70 years will likely cause mortality and extirpation of some amphibian species in the Southern Great Plains. My results demonstrate the threat to P. clarkii due to projected climate change and suggest that other amphibian species may also be vulnerable, particularly for anuran populations that are at the edge of their range such as Gastrophryne olivaea, a New Mexico state-endangered species. By combining field and laboratory techniques and coming to a similar conclusion, I have been able to provide conclusions about the effect of temperature and pH on amphibian survival and population persistence.Item Bioaccumulation and effects of metal contaminated soil on Great Plains toads, Bufo cognatus.(Texas Tech University, 2008-08) Bryer, Pamela Jean; McMurry, Scott T.; Cox, Stephen B.; Hooper, Michael J.; Carr, James A.Smelting and mining sites create local contaminated areas due to atmospheric release and deposition of metals and by increasing metal-enriched soil runoff. One of the proposed mechanisms of amphibian declines is contamination of habitats by chemical pollutants. Due to the number of mining and smelting sites worldwide, there is a risk to numerous amphibian populations from metal contamination. Currently, little is known about the effects of metal contaminated soil on amphibians. While it is generally understood that certain metals are highly toxic at low concentrations to most any organism, the exposure potential between organisms varies greatly. Metal uptake from soil is difficult to predict due to a complex metal-soil-water-toad relationship. Because of this complex relationship the use of models and passive sampling devices are not possible. This study consists of a series of soil exposures to toads Great Plains toads, Bufo cognatus. Each study follows the same basic design to assess metal bioaccumulation in toads housed individually on contaminated soil. The soils used in this study all came from or were created to mimic the soil conditions at the Anaconda Smelter Superfund Site, Deer Lodge County, MT, USA. The site is characterized by elevated levels of arsenic, cadmium, copper, lead, and zinc. Following their exposure, toads were tested through a series of behavioral, physiologic, and biochemical assays to asses the effects of the exposure. Between the studies, soil origin, soil temperature, size/age of the toads, and exposure duration were varied. Over the course of the studies, all metals showed increased bioaccumulation as soil metal concentration or exposure duration increased. Arsenic was not detectable in small, young-of-the-year toads. Cadmium concentrations, numerically, increased the most across each of the studies. Lead concentrations increased in most cases of increased exposure, however, variation in lead uptake in the adult toads studied was large as exposure duration increased. Zinc and copper tissue concentrations, both regulated essential metals, each increased with increasing exposure, however, zinc showed only slight to moderate increases overall. Partitioning within the body was highly variable between metals and between the studies. Overall, for juvenile toads, skin accumulated the bulk of the metals while in adults most metals accumulated in liver and kidney. One study compared the uptake of metals from soil collected at the Anaconda Smelter site to a series of spiked soils meant to mimic the ratio of metals in the Anaconda Smelter soil. Interestingly, we found that bioavailability was different between these soils, but not in the expected pattern. Cadmium and lead were both more bioavailable in the Anaconda Smelter soil than the spiked soil. Metal contaminated soil exposure had clear effects on the health of the toads. Time taken to bury was measured as a potential indicator of detecting contaminated soil avoidance, however, no differences were seen between soils. Although not consistent between each study the following endpoints were found to change in response to increasing soil metal concentration: prey orientating reflex, hop length, righting reflex, body mass, delta-aminolevulinic acid dehydratase (ALAD) activity, urine specific gravity, and mortality. Consistently across studies, organ (liver, kidney, and spleen) morphometrics did not change. It is clear, from this study and the works of others, that metal contaminated soil poses potential harm to amphibian populations. The effect of metal contaminated soil on toads can have two important ecological affects: 1) toads suffer directly from the presence of metal contaminated habitats and die, and 2) toads can accumulate metal concentrations that are then passed on via predation to other organisms in the food web. Protecting toads from metal contaminated soil is a challenge given their ability to bury deeply in the soil and their free ranging nature.Item Characterization and partial purification of DNase in Batrachochytrium dendrobatidis(2010-12) Maiti, Priyanka; San Francisco, Michael; Zak, John; Jeter, Randall M.The pathogen Batrachochytrium dendrobatidis (Bd) has been associated with amphibian declines in multiple continents, including western North America. Preliminary studies done in our laboratory have shown that Bd can form a biofilm and is active in the biofilm. We have identified DNase activity in Bd that may play a role in degrading the biofilm matrix and helping the organism to reinfect. DNase may also facilitate the supply of nutrients to the organism. Here we show the presence of this activity using qualitative and quantitative methods. DNase tests were performed using methyl green DNA containing plates and zymography. DNase activity is highest within a pH range of 5.5 to 7.5 and in the presence of Ca2+ and Mg2+ divalent cations. We have partially purified the enzyme and have seen that the enzyme may be present in 3 isoforms.Item Conservation of vertebrate biodiversity in Texas: Setting priorities for reserve selection(2006-12) Law, Jeffrey J.; Willig, Michael R.; McIntyre, Nancy E.; Cox, Stephen B.Species extinction rates are increasing throughout the world. A way to combat the global loss of species is through the creation of well-placed wildlife reserves. The principle objective of this study was to determine which areas throughout Texas most efficiently and effectively preserve extant vertebrate biodiversity (amphibians, reptiles, and mammals) if protected in reserves. Secondarily, I quantified the effectiveness of using a particular vertebrate class as a surrogate for others. The Sites Simulated Annealing Algorithm was used to determine areas that effectively preserve biodiversity while minimizing cost. This was accomplished through the use of irreplaceability values. Irreplaceability is equal to the number of times each planning unit is selected in a final solution to the SSAA. The SSAA was run 200 times for each scenario to determine this value. Species distribution maps obtained from the Texas GAP project were the basis for biodiversity data, whereas economic value of land came from the National Agriculture Statistics Service. I identified the best sites to establish reserves with current protected areas forced into the solution and also ignoring current protection status. The areas of the highest conservation concern, based on irreplaceability, were the Edwards Plateau of Central Texas and the Trans Pecos Region of West Texas. Although the irreplaceability values of planning units for incorporation into the reserve systems are correlated for all possible pairs of vertebrate classes, the associations are quite weak.Item Effect of anthropogenic disturbance and landscape structure on body size, demographics, and chaotic dynamics of Southern High Plains amphibians(Texas Tech University, 2002-05) Gray, Matthew JamesAmphibian populations are declining globally. Anthropogenic disturbance of landscapes surrounding wetlands may affect fitness, demographics, and dynamics of amphibian populations. Spatial positioning and relative connectedness of wetlands also may influence population demographics. Thus, I examined the effect of anthropogenic landscape use (cultivation vs. grassland) and structure on postmetamorphic body size (a fitness correlate), demographics, and dynamics of amphibians at 16 playa wetlands on the Southern High Plains (SHP) of Texas during 1999 and 2000. Amphibian populations were monitored using drift fence and pitfall traps, landscape structure was quantified using spatial analysis software, and dynamics were assessed using difference equations. Postmetamorphic body size of all amphibian species and age classes generally was greater at grassland than cropland playas, and in 1999 (i.e., a wetter year) than 2000. Abimdance of New Mexico and plains spadefoots (Spea multiplicata and S. bombifrons) generally was greater at cropland than grassland playas, and greater for barred tiger salamanders (Ambystoma tigrinum mavortium) in 1999 than 2000. Mean daily abundance of amphibians also was positively related to landscape structure indices representing geometric complexity and spatial positioning of wetlands. In general, as landscapes became more complex (e.g., numbers of edges increased) and inter-playa distance decreased, mean daily abundance of amphibians increased. Additional demographic analysis indicated that temporal niche partitioning existed in SHP amphibian populations; however, no differences existed between landuses. Lastly, biological chaos in the amphibian assemblage existed at 1 of 8 cropland and 7 of 8 grassland playas. A stochastic density-dependent Ricker function predicted chaotic dynamics most accurately. Anthropogenic disturbance surrounding wetlands affects body size, demographics, and dynamics of SHP amphibians. Spatial positioning of wetlands and landscape complexity may be as or more important than general landuse in affecting amphibian demographics. Annual differences in body size and abundance suggest rainfall may be important in influencing amphibian populations. Although spadefoot abundance was positively influenced by anthropogenic disturbance, I recommend retention and restoration of grasslands surrounding playa wetlands because landscape cultivation decreased body size and altered amphibian demographics and dynamics from an undisturbed state. These results have important implications in conservation biology, landscape ecology, and basic ecological and mathematical theory.Item Evaluation of anuran persistence in an urbanized drought-affected setting in the Southern High Plains(2012-12) Ramesh, Rasika; Griffis-Kyle, Kerry; Perry, Gad; Farmer, Michael; SanFrancisco, MichaelUrbanization, due to associated habitat degradation and fragmentation, is threatening amphibian survival worldwide. Mitigating urban amphibian declines is critical for amphibian conservation and requires understanding of amphibian life-histories and their use of urban landscapes. Since amphibian monitoring is non-existent in urban centers of the Southern High Plains, I conducted amphibian surveys in 2011 and 2012 in the city of Lubbock, west Texas, to establish fundamental baseline data regarding amphibian species occurring within the city, and evaluated site-suitability at site-specific and landscape scales at 23 urban lakes. While droughts are a recurring phenomenon here, the year 2011 broke past records for drought intensity and severity. I observed greater species richness and incidence of amphibian occurrence in 2012 which was relatively wetter; Bufonids (Anaxyrus speciosus and A. cognatus) were the most widespread. Using data from the drought, I attempted to establish a simple method to base management recommendations in the event of data scarcities associated with natural climatic extremes. This was used to create a preliminary grouping of lakes in order of amphibian management priority and level of management effort, thus emphasizing the importance of data gathered under drought conditions towards amphibian management efforts in the region.Item A review of the impacts of invasive grasses on herpetofauna(2015-08) Wright, Ian Michael; Gilbert, Lawrence E.; Leibold, Mathew ASpecies invasions pose one of the greatest threats to the maintenance and stability of biodiversity in ecosystems across the globe (Vitousek 1990). Plant species in particular are uniquely predisposed to successfully invade and establish themselves in novel habitats. In the United States alone invasive plants are responsible for nearly 35 billion dollars in economic and environmental damage. Grasslands are among the most productive ecosystems in the US and their biodiversity is threatened by continual introduction of alien grass species. These invasive grasses have a variety of direct and indirect effects on native grassland communities and have the ability to alter fire regimes, displace native species, and simplify grassland food webs. Little is known about the impacts invasive grasses have to amphibians and reptiles but there is evidence to suggest that these and other small organisms suffer direct mortality, impoverished prey sources, and reduced reproductive opportunities as a consequence of grass invasions. Here I summarize the current literature surrounding invasive grass impacts on herpetofauna and suggest topics of further research.