Abstract

Effective spatial management of coral reefs and marine protected area design require an understanding of genetic connectivity and biodiversity among reefs. We report a comparative analysis of connectivity (gene flow) in three commensal invertebrates and their host sponge, all of which display contrasting reproductive dispersal strategies: two spawners (the brittle star Ophiothrix lineata and the branching vase sponge Callyspongia vaginalis) and two brooders (the amphipods Leucothoe ashleyae and Leucothoe kensleyi). Mitochondrial DNA sequence variation was used to infer connectivity along 355km of the SE Florida coastline and among Caribbean islands. C. vaginalis showed the highest genetic structuring along the Florida coastline whereas the amphipods showed surprisingly high levels of gene flow despite a lack of pelagic larvae. In contrast to the brooders, both spawning species showed a strong pattern of genetic isolation by distance, and a Bayesian analysis of migration revealed a southerly bias to gene flow along the Florida coastline for the brittle star counter to the northerly flow of the Florida Current. Results among Caribbean and Florida locations were opposite to those obtained along the Florida coastline, as connectivity for all species was highly restricted. Furthermore, both amphipod species are divided into genetically highly divergent lineages across the Caribbean, suggestive of multiple cryptic species. Our results show that inferring connectivity based simply on reproductive dispersal strategies may be misleading, and highlight the need to integrate morphological taxonomy with genetic analysis to reveal the full extent of coral reef biodiversity

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