PAULAY, G.; MEYER, C. P.; University of Florida, Gainesville: Dispersal and divergence across the greatest ocean: Do larvae matter?

For benthic taxa, the duration of larval planktonic period is expected to correlate with dispersal ability, and thus with the extent of species ranges, at least in settings where planktonic dispersal is necessary to reach available habitats. The numerous islands of the tropical Pacific provide such a setting. However the most comprehensive analyses of larval period vs. species ranges across the Pacific show at most weak correlation. Studies of angelfishes, damselfishes, and wrasses show no correlation; in fact some of the taxa with the longest larval duration have the narrowest distributions. Although a correlation exists in cone snails, this is largely driven by differences between species that lack vs. those that have planktonic larvae. Finally taxa with very short larval life spans, like most bryozoans, often have wide Pacific ranges, implying other methods of dispersal governing their distributions. So do larvae matter in determining species ranges in the Pacific? We review several lines of evidence that indicate that larval life span indeed has a major imprint on structuring the distribution of tropical Pacific marine life. Taxa with poorer dispersal abilities show steeper drops in diversity from continental to insular areas of the Pacific than taxa with better dispersal abilities, although this pattern is weaker in deep water than on reef habitats. Emerging data on genetic differentiation also indicate that species with short planktonic periods tend to form species complexes comprised of mosaic patchworks of differentiated, narrowly-distributed, allopatric clades, while species with longer planktonic periods show gene flow across wide areas. We review a variety of evidence, and discuss the likely sources of conflict between these datasets.