Landscape and climate changes influence on taxonomic and functional richness of amphibians

Abstract

Deforestation and suppression of natural areas, called habitat loss, and the implementation of new land uses lead to species decline, extinctions, and dominance of generalist and disturbanceresistant species. In addition to changes in land use, the temperature increase, either alone or in synergy with other disturbances, causes extinction of those species unable to adapt or disperse to suitable places. Amphibians have life history characteristics that make them particularly sensitive to anthropogenic disturbances. The amphibian sensitivity to anthropogenic changes makes them ideal models to evaluate the impact, however the influence of these changes on their functional traits still is not clear. The objectives of this thesis were: i. to determine the amphibians sampling sufficiency according to the forest cover proportion, using automated recorders; ii. to define the main environmental predictors of the three components of amphibian diversity distribution (species, functional groups and functional traits) and to identify environmental thresholds responsible for the turnover of taxonomic or functional community; iii. to evaluate the climate changes effect on the taxonomic and functional richness of amphibians in the Atlantic Forest according to two scenarios of temperature increase. Using automated recording systems, a new data collect tool, I determined the amphibian richness and composition in each sampling landscape. The main results were: i. the amphibians sampling sufficiency is not related to the forest cover proportion; ii. Eucalyptus plantation, water bodies and environmental heterogeneity are the main predictors of the diversity components distribution. Thresholds of community turnover occur at the beginning of anthropogenic environmental gradients, except for environmental heterogeneity that showed the main threshold at the intermediate portion of its gradient. The different components have similar responses; iii. Climate changes will cause species loss and functions, but loss of function is more prominent. The conversion of natural areas into anthropogenic gradients causes species and function substitution, even though the gradient represents a small proportion of the landscape. However, environmental heterogeneity shows that the different land uses are beneficial for amphibians to the intermediate portion of the gradient, since the combination of natural and anthropic areas may offer different resources. The scenarios of temperature increase are negative for amphibians, functional redundancy will be compromised in the future, and both taxonomic and functional richness will be restricted mainly to southeastern Brazil in coastal areas. Regarding to the automated recording systems, I indicated a minimal sampling effort, however it is still necessary more studies to determine the ideal sampling effort. Both anthropogenic impacts have negative consequences for the amphibian community and the components of diversity present complementary responses, although similar in many cases.