Consequences of variable larval dispersal pathways and resulting phenotypic mixtures to the dynamics of marine metapopulations

Abstract

Larval dispersal can connect distant subpopulations, with important implications for marine population dynamics and persistence, biodiversity conservation and fisheries management. However, different dispersal pathways may affect the final phenotypes, and thus theperformance andfitness of individuals that settle into subpopulations. Using otolithmicrochemical signatures that are indicative of 'dispersive' larvae (oceanic signatures) and 'non-dispersive' larvae (coastal signatures), we explore the population-level consequences of dispersal-induced variability in phenotypic mixtures for the common triplefin (a small reef fish). We evaluate lipid concentration and otolith microstructure and find that 'non-dispersive' larvae (i) have greater and less variable lipid reserves at settlement (and this variability attenuates at a slower rate), (ii) grow faster after settlement, and (iii) experience similar carry-over benefits of lipid reserves on post-settlement growth relative to 'dispersive' larvae. We then explore the consequences of phenotypic mixtures in a metapopulation modelwith two identical subpopulations replenished by variable contributions of 'dispersive' and 'non-dispersive' larvae andfind that the resulting phenotypic mixtures can have profound effects on the size of themetapopulation. We show that, depending upon the patterns of connectivity, phenotypic mixtures can lead to larger metapopulations, suggesting dispersal-induced demographic heterogeneity may facilitate metapopulation persistence.