Thermal tolerance and sensitivity of amphibian larvae from Paleartic and Neotropical communities

Tese de mestrado, Biologia (Biologia da Conservação), 2009, Universidade de Lisboa, Faculdade de CiênciasAmphibians across the world are threatened by climate change. This work deals with the analysis of thermal tolerance and sensitivity and their latitudinal variation at the community level, with the intent of examining the prediction that tropical amphibians are at higher risk of extinction due to global warming than temperate species since their environmental temperatures are closer to their upper thermal limits. To test this prediction, two larval amphibian communities were selected from contrasting latitudes: subtropical (Argentina) and temperate Mediterranean (Iberian Peninsula) climates. In both locations, the following key parameters were obtained: 1) environmental pond temperatures (Thab), by monitoring ponds at different locations using water dataloggers; 2) critical thermal maximum, using a dynamic method called CTmax or knockdown temperature, to assess how close environmental temperatures are from their upper thermal limit; and 3) optimum temperature (Topt), by analysing tadpole's maximum swimming speed at different temperatures and building thermal performance curves (TPCs), to determine how changes in environmental temperatures will affect the ability to perform ecologically relevant functions and therefore their general fitness. Warming Tolerance (WT) (WT=CTmax-Thab) and Thermal Safety Margins (TSM) (TSM=Topt-Thab) were also calculated for all species. Analyses of CTmax and optimal performance temperature indicate that species have adapted their critical and optimal temperatures to cope with environmental conditions. Species exposed to higher maximum or average temperatures usually have higher CTmax or optimum temperatures, respectively. In addition, there is a significant positive correlation between these traits. Results also show that Argentinean subtropical species, although having higher CTmax and optimum temperature values, have lower WT and narrower TSM. Therefore, these species generally appear to be in greater extinction risk than temperate species from the Iberian Peninsula, under predicted scenarios of rising temperatures and climate changeResumo alargado em português disponível no document