Approaches using new data from co-sampled species permit rigorous statistical analysis but are often limited to a small number of species. While in recent years, there have been considerable advances in discerning spatial genetic patterns within species, the task of identifying common patterns across species is still challenging. Among the many possible causes of this incongruity, genetic drift provides the most compelling explanation: given massive effective population sizes of Indo‐Pacific species, even hard vicariance for tens of thousands of years can yield ΦST values that range from 0 to nearly 0.5. Among these, 15 had overwater distance as a significant predictor of pairwise ΦST, while 11 were significant for geographic or environmental barriers other than distance.Īlthough there is support for three previously described barriers, phylogeographic discordance in the Indo‐Pacific Ocean indicates incongruity between processes shaping the distributions of diversity at the species and population levels. Only 21 of 52 species analysed with dbRDA rejected the null model. Three of these barriers had median ΦST that were significantly larger than random expectation. Repeated coalescent simulation of a simple vicariance model yielded a wide distribution of pairwise ΦST that was very similar to empirical distributions observed across five putative barriers to gene flow. We observed a diversity of outcomes, although the majority of species fit a few broad biogeographic regions. We then weighed the relative contribution of distance versus environmental or geographic barriers to pairwise ΦST with a distance‐based redundancy analysis (dbRDA). Putative barriers to gene flow emerging from this analysis were evaluated for pairwise ΦST, and these ΦST distributions were compared to distributions from randomized datasets and simple coalescent simulations of vicariance arising from the Last Glacial Maximum. We tested eight biogeographic hypotheses for partitioning of the Indo‐Pacific using a novel modification to analysis of molecular variance. To test hypothesized biogeographic partitions of the tropical Indo‐Pacific Ocean with phylogeographic data from 56 taxa, and to evaluate the strength and nature of barriers emerging from this test.
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