Population genetics and biophysical modeling inform metapopulation connectivity of the Caribbean king crab Maguimithrax spinosissimus

Marine organisms with a short pelagic larval duration (PLD) are assumed to display significant population structure given low long-distance dispersal ability. For the wider Caribbean, theoretical and empirical considerations suggest that species with short PLDs inhabiting each of the following areas should be genetically distinct: Costa Rica (CR), Mexico (MX), and Florida Keys (FL-K), USA. This study tested the hypothesis of significant genetic differentiation in Maguimithrax spinosissimus populations across the wider Caribbean using a combination of biophysical modeling and population genetics. Biophysical modeling predicted dissimilar connectivity patterns among CR, MX, and FL-K depending upon assumed PLD. Eight days of dispersal only provided rare connections from MX to FL-K, and low likelihood multi-generational connections between CR and FL-K. In turn, 12 d of dispersal was sufficient to connect MX to FL-K through direct and indirect routes in biophysical models, but CR and FL-K remained connected only through multiple generational steps. After 16 d of dispersal, direct connections between CR and FL-K may occur, and by 20 d of dispersal, connections are likely between all sampled patches. Population genetic analyses based on partial sequences of the mtDNA 12S, 16S, and COI genes denoted the existence of a single, relatively high-frequency haplotype shared among all 3 populations, which suggests a longer PLD than predicted by laboratory study. In turn, an analysis of molecular variance and pairwise F _ST values demonstrated significant genetic differentiation among the studied populations. Altogether, the above information suggests low to moderate connectivity among populations in M. spinosissimus. Subpopulation split predictions suggest multi-generational or stepping-stone connectivity between CR and both MX and FL-K, and provides a framework for understanding the structure of M. spinosissimus metapopulations throughout the region. Overall, this study agrees with the notion of significant population structure in marine species with lower dispersal ability.