Journal
MOLECULAR ECOLOGY
Volume 21, Issue 22, Pages 5579-5598Publisher
WILEY
DOI: 10.1111/mec.12031
Keywords
amphidromy; habitat preference; Indo-Pacific; Isolation by distance; model selection; South Pacific
Funding
- Lerner-Grey Fund (American Museum of Natural History)
- Walter Sage Memorial Fund (Conchologists of America)
- NSF Doctoral Dissertation Improvement Grant [DEB-0508788]
- NSF [DEB-0338566, OCE-0349177]
- Australian Research Council [DP0878306]
- Kathryn Fuller Post-Doctoral Fellowship (World Wildlife Fund)
- NSF Coral Triangle Partnerships for International Research and Education [OISE-0730256]
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Marine species in the Indo-Pacific have ranges that can span thousands of kilometres, yet studies increasingly suggest that mean larval dispersal distances are less than historically assumed. Gene flow across these ranges must therefore rely to some extent on larval dispersal among intermediate stepping-stone populations in combination with long-distance dispersal far beyond the mean of the dispersal kernel. We evaluate the strength of stepping-stone dynamics by employing a spatially explicit biophysical model of larval dispersal in the tropical Pacific to construct hypotheses for dispersal pathways. We evaluate these hypotheses with coalescent models of gene flow among high-island archipelagos in four neritid gastropod species. Two of the species live in the marine intertidal, while the other two are amphidromous, living in fresh water but retaining pelagic dispersal. Dispersal pathways predicted by the biophysical model were strongly favoured in 16 of 18 tests against alternate hypotheses. In regions where connectivity among high-island archipelagos was predicted as direct, there was no difference in gene flow between marine and amphidromous species. In regions where connectivity was predicted through stepping-stone atolls only accessible to marine species, gene flow estimates between high-island archipelagos were significantly higher in marine species. Moreover, one of the marine species showed a significant pattern of isolation by distance consistent with stepping-stone dynamics. While our results support stepping-stone dynamics in Indo-Pacific species, we also see evidence for nonequilibrium processes such as range expansions or rare long-distance dispersal events. This study couples population genetic and biophysical models to help to shed light on larval dispersal pathways.
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