Phylogenetic ecology of octocoral - gastropod associations

Octocorallia (primarily soft corals and gorgonians) occur in cold-water environments as well as in tropical seas and can form a major component of reef communities. Because of their abundance and three-dimensional structure octocorals are an important habitat for symbiotic species such as crustaceans, worms, fishes and molluscs. Among the latter group are snails of the family Ovulidae, obligate associates of octocorals. Ovulid snails have adapted their morphological appearance to avoid predation. They can either be perfectly camouflaged or ambiguously coloured to advertise their toxic properties. It was therefore expected that these morphological adaptations would have an evolutionary background, which would corresponds with that of their octocoral hosts. In this thesis the evolutionary history of the Ovulidae and Octocorallia are examined within and between both taxa by using a multifaceted approach, consisting of (calibrated) phylogenetic and co-evolutionary analyses, taxonomic revisions and coral bioactivity research. The results show that snails and octocorals did not coevolve, but that the evolutionary history between both groups is best described as sequential evolution in which the host affects the symbiont but not vice versa.