Chemical defense of an exotic coral as invasion strategy

The invasion success of exotic species has been frequently correlated to abiotic and biotic features of the receptor region and to the biological aspects of the invasive organism. There is, however, no information about defensive chemicals found in invasive species as strategy that could promote or facilitate an invasion in a marine environment. We conducted experimental field assays to verify the potential of secondary metabolites of an Indo-Pacific exotic soft coral, Stereonephthya aff. curvata, as a defensive chemical against generalist fish and as an allelopathic agent against the potential local competitor-the gorgonian Phyllogorgia dilatata-in Arraial do Cabo, on the southeastern coast of Brazil. As a result of our experiments, it was confirmed as an efficient chemical defense against fishes by crude coral hexanic extract. In addition to its role as defense against consumers, the field experimental assay also verified that chemicals from this exotic coral had an allelopatic effect causing large necrosis on tissues of the Brazilian endemic gorgonian P. dilatata. Both defensive strategies observed may facilitate the perpetuation and/or expansion and characterize an expressive, invasive facilitator for S. aff. curvata. The obtained results indicate that this exotic coral species may be a real threat to the biological integrity of the Arraial do Cabo Harvest Reserve, Rio de Janeiro. In addition, the study reveals that defensive chemicals can be used to predict the potential invasiveness of introduced species.