The evolutionary history of parasitic gastropods and their coral hosts in the Indo-Pacific

Abstract

This thesis deals with the associations between parasitic snails and their mushroom coral hosts. Gittenberger has spent 800 hours under water and searched about 60,000 coral discs for these parasites. He dived in Egypt, the Maldives, Thailand, Malaysia, Japan, Palau, the Philippines, Indonesia and Australia. Places that are less popular with divers, like very deep or shallow sites, areas with strong currents, murky water, or sandy bottoms, received special attention. The greatest biodiversity was found off Sulawesi, a region that needs protection. Except for shell morphology, molecular, anatomical and ecological characters of the snails were studied. As a result it turned out that many more species exist than hitherto thought. Some dozens of unnamed cryptic ones were discovered. These can be distinguished most clearly by their DNA and their host specificity. The species of parasitic snails evolved most probably by bypassing the defence mechanism of one or a few coral species. Most of the data support a sympatric speciation model for these taxa. The molecular phylogenies of the parasites and their hosts were compared to investigate the amount of co-evolution.