Connectivity dominates larval replenishment in a coastal reef fish metapopulation

Abstract

Direct estimates of larval retention and connectivity are essential to understand the structure and dynamics of marine metapopulations, and optimize the size and spacing of reserves within networks of marine protected areas (MPAs). For coral reef fishes, while there are some empirical estimates of self-recruitment at isolated populations, exchange among sub-populations has been rarely quantified. Here we used microsatellite DNA markers and a likelihood-based parentage analysis to assess the relative magnitude of self-recruitment and exchange among 8 geographically distinct sub-populations of the panda clownfish Amphiprion polymnus along 30 km of coastline near Port Moresby, Papua New Guinea. In addition, we used an assignment/exclusion test to identify immigrants arriving from genetically distinct sources. Overall, 82% of the juveniles were immigrants while 18% were progeny of parents genotyped in our focal metapopulation. Of the immigrants, only 6% were likely to be genetically distinct from the focal metapopulation, suggesting most of the connectivity is among sub-populations from a rather homogeneous genetic pool. Of the 18% that were progeny of known adults, two thirds dispersed among the 8 sub-populations and only one third settled back into natal sub- populations. Comparison of our data with previous studies suggested that variation in dispersal distances is likely to be influenced by the geographic setting and spacing of sub-populations.