Larval ecology, dispersal, and the evolution of sociality in the sea

Individual decisions about whether or not to disperse shape the kin structure of social groups, promoting or disrupting the evolution of sociality via kin selection. It is often assumed that the great dispersal potential of marine larvae driven by ocean currents disrupts kin association and, as a consequence, reduces the chances that social groups in the sea form via kin selection. Yet, accumulating evidence indicates that the larval dispersal process is not as random as previously assumed and that different mechanisms can promote kin associations in marine species. Here, we review recent findings in the marine larval ecology literature, emphasizing key aspects of larval development that may limit or promote dispersal and the evolution of sociality in the sea. We find ample evidence that marine larvae settle closer to home than has been previously assumed. A variety of different mechanisms, including lack of planktonic dispersal, limited larval duration, larvae traveling together, variability in reproductive success, and behavioral and physical processes, can generate kin association in marine species and potentially lead to the formation of social groups via kin selection. Uncovering post-settlement dispersal patterns is also important for understanding how groups of unrelated individuals are formed. By integrating different larval dispersal strategies into the dual benefit framework for the evolution of sociality, we provide examples of alternative pathways for the evolution of sociality in marine species. Finally, we discuss how the increased use of parentage analysis in marine species will provide an opportunity for investigating whether kin selection is indeed much rarer in marine than terrestrial species. Ultimately, determining the role that dispersal and kin selection play in the evolution of sociality in marine species will require an increased effort to gather both behavioral and genetic data for the same species.