PS 30-12
Rainfall changes favoured tolerant groups independently of resource diversity
Climate and biodiversity are changing at an unprecedented rate. Many studies have focused on these themes separately but the realistic ecological context includes the interaction among them. The study of biological impacts of climate change usually focuses on the most vulnerable species, leaving behind the tolerant ones. The persistence of those species must be the key for the maintenance of trophic interactions and ecosystem processes in a changing environment. Beyond that, there are few informations about how predicted rainfall changes are going to affect aquatic ecosystems, mainly due to the experimental challenge to manipulate the foreseen alterations in ecosystem scales. Alternatively, experiments using natural microcosms as tank-bromeliads have shown a great potential to test ecological theories. We experimentally verified the effects of litter diversity and changes in rainfall on the well-known tolerant group, Bdelloidea rotifers. Bdelloidea rotifers are abundant in many water bodies and their wide ecological range, obligatory parthenogenetic and ability to survive after drought events make them tolerant and excellent pioneering organisms. We used a full-factorial design, composed by five predicted rainfall scenarios crossed with all combinations of three litter species, the main food resource for bdelloids. Rainfall scenarios were based on precipitation projections for Southeastern Brazil.
Results/Conclusions
Rainfall changes consistently affected the bdelloids densities in face of the occurrence of extreme events (GLM; F 4,160 = 3.001, P = 0.020) but no effect of litter diversity was found (GLM; F 1,164 = 0.162, P = 0.687). While the bromeliads were filled, the extreme rainfall scenarios represent a suitable habitat for colonization and reproduction. Previous studies showed that the fitness of cyclically desiccated bdelloids populations never declines and their fecundity is equal or even higher than those exposed to constant hydrated conditions. We suggest that litter diversity did not influence bdelloids densities because: 1) they are generalist detritivores and more affected by quantity than food quality; 2) they main feed on particulated organic matter (POM), as the rain dilutes the POM in tank-bromeliads, it decreases the relative importance of the litter identity− they have access to a better resource but in smaller amounts. Therefore, the ability to survive and to have better performances after drought events increase the bdelloids importance on trophic interaction in aquatic ecosystems in face of climate change disturbances.