The formation of marine kin structure : effects of dispersal, larval cohesion, and variable reproductive success

Abstract

The spatial distribution of relatives has profound e ects on kin interactions, inbreeding, and inclusive tness. Yet, in the marine environment, the processes that generate patterns of kin structure remain understudied because larval dispersal on ocean currents was historically assumed to disrupt kin associations. Recent genetic evidence of co-occurring siblings challenges this assumption and raises the intriguing question of how siblings are found together after a (potentially) disruptive larval phase. Here, we develop individual based models to explore how stochastic processes operating at the individual level a ect expected kinship at equilibrium. Speci cally, we predict how limited dispersal, sibling cohesion, and variability in reproductive success di erentially a ect patterns of kin structure. All three mechanisms increase mean kinship within populations, but their spatial e ects are markedly di erent. We nd that: (1) when dispersal is limited, kinship declines monotonically as a function of the distance between individuals; (2) when siblings disperse cohesively, kinship increases within a site relative to between sites; and (3) when reproductive success varies, kinship increases equally at all distances. The di erential e ects of these processes therefore only become apparent when individuals are sampled at multiple spatial scales. Notably, our models suggest that aggregative larval behaviors, such as sibling cohesion, are not necessary to explain documented levels of relatedness within marine populations. Together, these ndings establish a theoretical framework for disentangling the drivers of marine kin structure.