Amphibian populations are rapidly declining worldwide. Although individual factors may have large local influences, worldwide declines are attributed to interacting global stressors including rising temperatures and environmental pollutants. Globally, water temperatures closely track rising air temperatures and increase the metabolic rates of aquatic ectotherms, changing the rates of uptake, biotransformation, and excretion of contaminants, such as metals. To test how interactions of multiple, chronic stressors affect amphibian growth, I exposed Cope's gray treefrogs (Hyla chrysoscelis) in an outdoor mesocosm facility to three temperature regimes (ambient, ambient +1.5 oC, ambient +2.5 oC) in filtered lake water amended with mixtures of cadmium, copper, and lead ranging from 3.7 to 26.7 risk quotients (relative to the chronic concentration criteria protective of freshwater organisms). Temperature shifts and sublethal metals concentrations significantly affected the energetics of tadpoles as assessed by non-parametric and parametric analyses. Regression analyses indicated no significant relationship between temperature and time to forelimb emergence at the three lowest metals concentrations, but the relationship was parabolic at the three highest concentrations, indicating a differential effect of temperature across a gradient of water quality. The concept that tadpoles increase developmental rates to escape unfavorable aquatic conditions was supported at each temperature by shortened time to forelimb emergence (Gosner Stage 42) at the second highest metals concentration. This response, however, was overwhelmed by the energetic costs associated with the highest concentration and the highest temperature. Moreover, these parabolic relationships match predictions based on species specific thermal windows and pejus temperatures. My findings indicate that global warming may affect contaminated waters to a greater extent than pristine aquatic ecosystems, and that the primary effect may be diminished pejus and critical thermal maximum temperatures, and a narrowing of the species' thermal window.

Made available in DSpace on 2016-08-15T20:31:29Z (GMT). No. of bitstreams: 1 FabianoLO_DISSERT.pdf: 1435099 bytes, checksum: b17929f018436cbdd2c8d22fb8f9caf0 (MD5) Previous issue date: 2016-02-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Stingless bee species that occur in the Brazilian semiarid region are adapted to the hot and dry climate of the region. Additionally, the availability of floral resources varies greatly throughout the year. Thus, climatic factors associated with variation in resource availability may be important determinants for the external activities of stingless bee colonies in this ecoregion. The foraging activities are critical for the maintenance of colonies, since they are important to supply the colonies with food (pollen and nectar) and materials for construction and defense of the colony (resin). In the present study, I analyzed the abiotic conditions, mainly external ambient temperature, nest-internal temperature and relative humidity, and investigated whether and to which extent these variables are related to and interact with the foraging activity of Plebeia aff. flavocincta in the Brazilian semiarid region, where these bees naturally occur. The peak foraging activity of the bees was in a temperature range between 32-34°C. The colonies of Plebeia aff. flavocincta intensified their nectar and pollen collection in months with elevated precipitation, when resources in the environment were abundant. In the dry period, by contrast, foraging activity was genearlly low. The colonies adjusted their foraging activity to the given climatic conditions, which points to behavioral adaptations of this bee species to the environmental unpredicatbility of the Brazilian semiarid region / Espécies de abelhas sem ferrão que ocorrem no semiárido brasileiro são adaptadas ao clima quente e seco dessa região. No semiárido brasileiro os recursos florais disponíveis para a alimentação das abelhas variam muito ao longo do ano. Os fatores climáticos associados à variação na disponibilidade de recursos podem definir as atividades externas das colônias. Esses atividades são fundamentais para a manutenção das colônias, uma vez que suprem a colônia de alimentos (pólen e néctar) e outros materiais para construção e defesa da colônia (resina) Nesse sentido, foi analisado as condições abióticas principalmente temperatura ambiental externa, interna e umidade relativa sendo verificado que estas variáveis estão relacionadas e interagem com atividade de voo de Plebeia aff. flavocincta no semiárido brasileiro e no bioma Caatinga onde estas estão inseridas. Também foi verificado que as condições abióticas que favoreceram o pico dos principais recursos coletados por estas abelhas estão em uma faixa de temperatura entre 32 a 34 °C. A atividade de voo de Plebeia aff. flavocincta aumenta as coletas intensificando suas atividades externas, quando há recursos em grande quantidade, como nos meses de maior precipitação principalmente no que refere-se aos principais recursos como pólen e néctar, já que neste período há uma maior oferta de recursos florais, enquanto no período seco, houve atividade, mas não na mesma intensidade. As colônias destas abelhas ajustam a atividade forrageira aumentando tanto a atividade individual como também a força de trabalho colonial e que portanto os resultados aqui encontrados sugerem ajustes comportamentais às variações ambientais da região semiárida em respostas as mudanças e demandas da colônia