Evolutionary diversification of coral-dwelling gall crabs (Cryptochiridae)
Gall crabs (Crustacea : Cryptochiridae) are small, coral-dwelling crabs that live in obligate association with their host corals (Scleractinia), on which they rely for food and shelter. They have been recorded from shallow and deeper waters (over 500 m), but the majority of the species live in reef corals in the photic zone. The highest number of species is recorded from the Indo-West Pacific, where coral diversity is highest. This PhD thesis deals with various aspects of their evolution and diversification; four species are described as new to science, and the host specificity, biogeography, distribution and reproductive morphology of gall crabs are studied. In addition, the close association between gall crabs and corals allowed for studies on (cryptic) speciation and possible coevolution. Results show that the observed coevolutionary events should most probably be ascribed to sequential evolution, which indicates that the phylogeny of the gall crabs has been directed by the evolution of the corals.