Meeting Abstract
Crabs in the superfamily Majoidea have an abbreviated larval development, with fewer zoeal molts than most other brachyuran groups. A possible consequence of a shortened planktonic stage is reduced dispersal ability. This, in turn, may restrict gene flow between populations and lead to genetic structuring of taxa across geography. Populations of several widespread species in the superfamilies Majoidea, Xanthoidea, and Grapsoidea were sampled from western and eastern Australia, the Line Islands, French Polynesia, Hawaii, and the southwest Indian Ocean. Mitochondrial CO1 DNA sequences were obtained from multiple individuals at each location, and phylogenetic trees were constructed to evaluate geographic differentiation. Results show that most widespread majoid crabs are species complexes of highly differentiated, reciprocally monophyletic Evolutionarily Significant Units, often limited to single archipelagoes. In contrast, most xanthoid and grapsoid crabs appear to be truly wide-ranging, sharing haplotypes across distant localities. These results lend support to the hypothesis that planktonic larval duration is an important determinant of geographic differentiation.
