Larval exchange among marine populations is a vital driver of population dynamics and detecting these connectivity patterns has the potential to inform conservation actions. But accurately measuring the dispersal of tiny larvae in the ocean remains challenging. Consequently, empirical dispersal kernels have been measured for only a few marine species. In this study, we obtained indirect dispersal estimates using an isolation-by-distance (IBD) model in the coral reef fish Elacatinus lori and assessed the accuracy of these estimates by comparing them to direct measurements of dispersal from genetic parentage analysis. Specifically, drawing on the IBD slope and effective population density, we indirectly estimated sigma (𝜎), the spread of a dispersal distribution.
Results/Conclusions
While the spread of the directly measured dispersal distribution was σ = 3.93 km (95% CI: 3.29 – 4.71 km), the spread of the IBD dispersal distribution was σ = 4.10 km (95% CI: 3.23 – 5.03) and σ = 2.90 km (95% CI: 2.26 – 3.59), assuming a random or monogamous mating system, respectively. Parameterizing Laplace dispersal kernels with these values of σ yielded patterns that were remarkably similar to a kernel fit to the direct parentage data. We also found that, like many marine fishes, E. lori has a large effective population size. However, uncertainty in effective size did not ultimately have a strong effect on the IBD-based dispersal estimates. Taken together, these findings illustrate that accurate dispersal estimates can be produced by indirect IBD methods and suggest that this more feasible approach to estimating dispersal may be broadly applicable to the study of marine larval dispersal.
