Effects of top predator loss and climate changes on microbial community stability on tank bromeliad phytotelmatas : Efeitos da perda do predador de topo e mudanças climáticas na estabilidade de comunidades microbianas de fitotelmatas de bromelias-tanque

Abstract

Global changes are modifying the functioning of several essential ecosystem processes. Knowing how ecological stability responds to the different disturbances caused by the anthropic impact has become an issue of enormous relevance. The gradual increase of temperature over the last decades poses serious risks to biodiversity. Species extinction rates have become even larger. This loss does not occur randomically, such that predator loss has occurred at more disturbing rates, since top predators appear to be more sensitive to environmental variations and usually have small populations. Predator loss may change trophic cascades and compromise the food web stability, especially in distinct climate change scenarios. We investigated in this dissertation the isolated and interactive roles of climate warming and top predator loss in the temporal stability of ecological communities under different levels of ecological organization, using as a study model the microbial communities present in phytotelmatas of tank bromeliads. The results indicate that these global change drivers can influence the temporal stability of the community through direct and indirect effects on microbial density and diversity, mediated by releasing of mesopredators (Culicidae) from the top-down control. The system responded more intensely to the effect of top predators than to warming, and did not respond to interactive effects between them. In addition, different ecological organization levels responded to different attributes of mesopredators: while greater culicid abundance reduced diversity and stability at community level, increased culicid richness decreased such properties at individual trophic levels. Finally, cascading effects of mesopredator release weakened ecological mechanisms that promote stability, like portfolio effect and asynchrony, indicating potential decreasing of asymmetry on the species responses to environmental and biotic variations. This study shows new perspectives to understanding the diversity-stability relationship, highlighting that top predators and trophic cascades can be determinant factors as or more important than climate for maintaining ecological stability.