Global warming and thermal sensitivity of amphibian larvae

MARCO KATZENBERGER, MIGUEL TEJEDO, HELDER DUARTE, FEDERICO MARANGONI, DIEGO BALDO, DARDO A. MARTI, JUAN F. BELTRAN, RICK RELYEA, MIRCO SOLÉ

Salvador de Bahia

Congreso; VI Congresso Brasileiro de Herpetologia; 2013

During the past century, the Earth has experienced a mean increase in temperature of 0.6 °C, reaching up to 4 °C in the most northern latitudes, which has already caused significant changes in species? distribution patterns, the structure and functioning of ecosystems and the timing of biological processes. Ectotherms constitute the majority of current biodiversity and their basic physiological functions (e.g. locomotion, growth, or reproduction) are strongly influenced by environmental temperature, which makes them especially vulnerable to climate warming. Recent studies suggest that tropical ectotherms from lower latitudes face considerably higher risk from environmental warming than do their temperate counterparts. In this study, we determine the thermal safety margins (difference between the species? thermal optimum (Topt) and its current(mean) environmental temperature) of over 70 larval amphibian species and evaluate their vulnerability to global warming. Species were sampled mainly from five different thermal regions: North-American temperate community (USA), European temperate community (Iberian Peninsula), subtropical Chaco community (Argentina), subtropical Misiones community (Argentina), and low-land tropical community (Brazil). In each species? collecting site, we placed a water datalogger to measure environmental temperatures during breeding season. Thermal performance curves (TPCs) were based on locomotor performance by measuring tadpoles maximal burst swimming speed (i.e. sprint speed) at different temperatures. These TPCs were then used to estimate optimum temperature for each species. Our results indicate there is phylogenetic signal so that closely related taxa tend to have more similar optimum temperatures than distant taxa, as seen in critical thermal maximum data from previous works. Similarly, optimum temperature is also related to environmental temperatures, which indicates that habitat is acting as a selective force and species have adapted their optimum temperature to cope with current environmental temperatures. As there can be much optimum temperature variation in the same latitude as in a latitudinal gradient, for a correct assessment of the vulnerability to increasing temperatures, it is rather important to consider the species? microhabitat. Having a high optimum temperature does not necessarily reflect broader thermal safety margins (TSM). Although species living at very hot environments tend to have higher optimum temperatures, such as those from the Chaco region, they are also exposed to higher environmental temperatures, which can make them more vulnerable to global warming.