Diversification on coral reefs

Ecological speciation remains one of the long-standing questions in evolutionary biology, especially when no natural barriers are present. The importance of gene flow in speciation will be studied in a tropical marine ecosystem, with obligate coral-dwelling gall crabs (Cryptochiridae) as the model taxon. These crabs show varying degrees of host-specificity on scleractinian corals. Field studies will be conducted to assess the influence of depth and environmental factors on host occurrence rates of the crabs, and test for biogeographic patterns. The evolution of the symbiotic crabs will be first studied using co-phylogenetic methods. Subsequently, next-generation sequencing tools (RADseq) will be used to study intraspecific divergence and potentially cryptic speciation in the crabs. It is expected that host shifting can lead to ecological speciation, hence being a common mode of divergence in obligate tropical marine symbiont fauna. This study will contribute to our overall understanding of speciation, by assessing the relevance of gene flow in speciation on coral reefs.