Meeting Abstract
Deciphering evolutionary and ecological factors that contribute to population divergence has been challenging in marine species, which oftentimes have few barriers to dispersal and low levels of population differentiation. However, environmental variables such as oceanic currents and post-settlement habitat differences can reduce gene flow resulting in fine-scale genetic structure, particularly at loci under selection. The waterfall-climbing Hawaiian goby fish, Sicyopterus stimpsoni, has a marine larval dispersing phase yet experiences post-settlement selection (predation and climbing), which varies in disparity with stream geomorphology and corresponds to observed differences in body shape. Here, we analyzed population structure of S. stimpsoni across the archipelago by combing genotyping by sequencing with oceanographic models of passive dispersal and individuals-based models of natural selection. Neutral loci showed low, fluctuating, yet significant genetic structure, whereas loci potentially under selection showed strong genetic structure between populations with different post-settlement selective regimes. However, mismatches between our model connectivity matrices and observed patterns of population structure demonstrated that when either local retention or self-recruitment is increased, combined with post-settlement selection, our fit between simulated and observed patterns of genetic structure improves. Our results suggest that comparing observed patterns of population differentiation to models of gene flow, drift and selection yields new insights into how populations of marine dispersing organisms may diverge and potentially lead to speciation in an environment conducive to high connectivity.
