Browsing by Subject "Amphibians"
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Item Amazonian Amphibian Diversity Is Primarily Derived from Late Miocene Andean Lineages(Public Library of Science, 2009-03-10) Santos, Juan C; Coloma, Luis A; Summers, Kyle; Caldwell, Janalee P; Ree, Richard; Cannatella, David CThe Neotropics contains half of remaining rainforests and Earth's largest reservoir of amphibian biodiversity. However, determinants of Neotropical biodiversity (i.e., vicariance, dispersals, extinctions, and radiations) earlier than the Quaternary are largely unstudied. Using a novel method of ancestral area reconstruction and relaxed Bayesian clock analyses, we reconstructed the biogeography of the poison frog clade (Dendrobatidae). We rejected an Amazonian center-of-origin in favor of a complex connectivity model expanding over the Neotropics. We inferred 14 dispersals into and 18 out of Amazonia to adjacent regions; the Andes were the major source of dispersals into Amazonia. We found three episodes of lineage dispersal with two interleaved periods of vicariant events between South and Central America. During the late Miocene, Amazonian, and Central American-Chocoan lineages significantly increased their diversity compared to the Andean and Guianan-Venezuelan-Brazilian Shield counterparts. Significant percentage of dendrobatid diversity in Amazonia and Chocó resulted from repeated immigrations, with radiations at <10.0 million years ago (MYA), rather than in situ diversification. In contrast, the Andes, Venezuelan Highlands, and Guiana Shield have undergone extended in situ diversification at near constant rate since the Oligocene. The effects of Miocene paleogeographic events on Neotropical diversification dynamics provided the framework under which Quaternary patterns of endemism evolved.Item Application Of Stable Isotope Analysis To Study Temporal Changes In Foraging Ecology In A Highly Endangered Amphibian(Public Library of Science, 2013-01-15) Gillespie, J. HayleyBackground -- Understanding dietary trends for endangered species may be essential to assessing the effects of ecological disturbances such as habitat modification, species introductions or global climate change. Documenting temporal variation in prey selection may also be crucial for understanding population dynamics. However, the rarity, secretive behaviours and obscure microhabitats of some endangered species can make direct foraging observations difficult or impossible. Furthermore, the lethality or invasiveness of some traditional methods of dietary analysis (e.g. gut contents analysis, gastric lavage) makes them inappropriate for such species. Stable isotope analysis facilitates non-lethal, indirect analysis of animal diet that has unrealized potential in the conservation of endangered organisms, particularly amphibians. Methodology/findings -- I determined proportional contributions of aquatic macroinvertebrate prey to the diet of an endangered aquatic salamander Eurycea sosorum over a two-year period using stable isotope analysis of 13/12C and 15/14N and the Bayesian stable isotope mixing model SIAR. I calculated Strauss’ dietary electivity indices by comparing these proportions with changing relative abundance of potential prey species through time. Stable isotope analyses revealed that a previously unknown prey item (soft-bodied planarian flatworms in the genus Dugesia) made up the majority of E. sosorum diet. Results also demonstrate that E. sosorum is an opportunistic forager capable of diet switching to include a greater proportion of alternative prey when Dugesia populations decline. There is also evidence of intra-population dietary variation. Conclusions/significance -- Effective application of stable isotope analysis can help circumvent two key limitations commonly experienced by researchers of endangered species: the inability to directly observe these species in nature and the invasiveness or lethality of traditional methods of dietary analysis. This study illustrates the feasibility of stable isotope analysis in identifying preferred prey species that can be used to guide conservation management of both wild and captive food sources for endangered species.Item Contributions to Geology, 1944(University of Texas at Austin, 1944-01-01) University of Texas at Austin. Bureau of Economic GeologyItem Global Conservation Significance of Ecuador's Yasuní National Park(Public Library of Science, 2010-01-19) Bass, Margot S.; Finer, Matt; Jenkins, Clinton N.; Kreft, Holger; Cisneros-Heredia, Diego F.; McCracken, Shawn F.; Pitman, Nigel C. A.; English, Peter H.; Swing, Kelly; Villa, Gorky; Di Fiore, Anthony; Voigt, Christian C.; Kunz, Thomas H.Background -- The threats facing Ecuador's Yasuní National Park are emblematic of those confronting the greater western Amazon, one of the world's last high-biodiversity wilderness areas. Notably, the country's second largest untapped oil reserves—called “ITT”—lie beneath an intact, remote section of the park. The conservation significance of Yasuní may weigh heavily in upcoming state-level and international decisions, including whether to develop the oil or invest in alternatives. Methodology/Principal Findings -- We conducted the first comprehensive synthesis of biodiversity data for Yasuní. Mapping amphibian, bird, mammal, and plant distributions, we found eastern Ecuador and northern Peru to be the only regions in South America where species richness centers for all four taxonomic groups overlap. This quadruple richness center has only one viable strict protected area (IUCN levels I–IV): Yasuní. The park covers just 14% of the quadruple richness center's area, whereas active or proposed oil concessions cover 79%. Using field inventory data, we compared Yasuní's local (alpha) and landscape (gamma) diversity to other sites, in the western Amazon and globally. These analyses further suggest that Yasuní is among the most biodiverse places on Earth, with apparent world richness records for amphibians, reptiles, bats, and trees. Yasuní also protects a considerable number of threatened species and regional endemics. Conclusions/Significance -- Yasuní has outstanding global conservation significance due to its extraordinary biodiversity and potential to sustain this biodiversity in the long term because of its 1) large size and wilderness character, 2) intact large-vertebrate assemblage, 3) IUCN level-II protection status in a region lacking other strict protected areas, and 4) likelihood of maintaining wet, rainforest conditions while anticipated climate change-induced drought intensifies in the eastern Amazon. However, further oil development in Yasuní jeopardizes its conservation values. These findings form the scientific basis for policy recommendations, including stopping any new oil activities and road construction in Yasuní and creating areas off-limits to large-scale development in adjacent northern Peru.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.Item The ecology of amphibian-associated bacterial communities(2020-03-03) Correa Filho, Decio Tadeu; Matz, Mikhail V.; Leibold, Mathew A.; Bolnick, Daniel; Rodriguez, David; Ryan, Michael; Mueller, UlrichMulticellular organisms are habitat for a diverse bacterial community (microbiome) that can often be associated with host health and well-being. To better understand that relationship I explored several ecological aspects of the host-associated microbiomes using pre- and post-metamorphic amphibians. First, I investigated the relative roles of local selection (due to host species identity) and regional effects (due to water body identity) on the community structure of the gut microbiome of tadpoles. I found that each water body represents a relatively distinct species pool of bacteria available for community assembly, making the water body more important in shaping the microbiome of tadpoles than their species identity. I then showed that the gut microbiome of tadpoles is not homogeneous throughout its gut length as there are changes in composition, abundance, richness, and diversity from the anterior to the posterior parts of the gut. Moreover, the gut microbiome of the anterior portion is unstable, i.e., it is highly influenced by exposition to external bacteria, while the microbiome of the posterior gut has higher stability. The posterior part harbors the functional microbiome that helps tadpoles with digestion. In fact, I found that most of the essential amino acids in the tadpole tissue are derived from bacteria. I then manipulated their gut microbiome and diet and found that the composition of the microbiome can have profound impacts on the performance and fitness of the tadpole, as distinct microbiomes affect growth, development, and mortality of the host. Finally, as tadpoles metamorphose and leave the water, their microbiome is reshaped due to changes in conditions related to both the environment and the host. I tested and showed that closely related species of adult amphibians have a tendency to harbor similar skin microbiome, but the same signal was not found for their gut microbiome. In summary, I found that the gut of tadpoles harbor several distinct but connected microbiomes that vary in composition, diversity, and stability and that can profoundly affect the fitness of the host. Its composition is ultimately determined by the environmental bacteria tadpoles were exposed to. For adult amphibians, closely related species have more similar skin but not gut microbiome.