Ecologia e Fisiologia - Comunicações orais

Ascidians are sessile animals that have adopted many strategies to survive predation and dominate reef communities worldwide. Chemical and physical defences, or even coloniality, are considered the main ascidian strategies to escape predation. Unpalatability through chemical defences has been confirmed in manipulative experiments using pellets or tissues of ascidians. However, predation exclusion experiments on the community scale show that ascidians are almost entirely preyed upon when exposed to predators. Based on these contrasting results, we performed a meta-analysis to assess the importance of the place of the implementation of the experiment, the experiment design, ascidians’ sociability, and predator’s type to the efficacy of ascidians' defences. We found that multiple factors, such as methodology and the identity of predators but not ascidians’ sociability, can interfere with the effectiveness of the defences of ascidians. Studies that tested the palatability of ascidians against predators using pellets or tissues presented evidence for ascidians’ defences, however, they depend on the predator’s identity. We did not find evidence of ascidians’ defences in the studies that tested the effect of predators on ascidians in the community. There is a lack of field experiments, mainly on solitary ascidians, that evaluate ascidians’ predation in communities of natural or even artificial substrate. Research on ascidian defences is also biased toward the temperate region from the northern hemisphere. The common knowledge that ascidians are animals with active defences may be overestimated and defences are probably restricted to a limited number of species. This misconception is caused mainly by methodological and geographical biases that test only species with previous evidence of defences. Therefore, we need more worldwide studies focusing on the ecological relationships between ascidians and their natural predators.