Pelagic Larval Duration and Isolation by Distance in Coastal Species

Dispersal among populations is crucial both for demographic stability and for the evolutionary potential of species. In marine organisms, dispersal has been shown to be prevalent during pelagic early life stages. Consequently, pelagic larval duration (PLD) has been proposed as an important driver of gene flow in marine species and is influencing genetic differentiation among populations. Despite this prediction, empirical studies have often failed to find the expected correlation between PLD and genetic metrics of gene flow. This could mean either that PLD is a poor predictor of gene flow or that differences in methodology, oceanography or sampling design across studies obscure the underlying mechanisms of gene flow. In the present study, we address these issues by using a consistent sampling design for 10 coastal species with previously published genetic data (ddRAD and microsatellites), and that differ in PLD. We investigate gene flow using an isolation-by-distance (IBD) model with pairwise <i>F</i> _ST-estimates regressed against distances measured along the prevailing coastal ocean current in the study region. We find a significant (<i>p</i> < 0.05) correlation between species' PLD and IBD slopes, with a moderately strong correlation (<i>r</i> ² > 0.5), These findings support the notion of PLD as a key factor determining dispersal and gene flow among populations of coastal species. Our findings reiterate genetics as a useful tool for inferring population dispersal in marine organisms when potentially confounding factors are eliminated by adopting a consistent sampling design.