Going against the flow: Maintenance of alongshore variation in allele frequency in a coastal ocean

Abstract

Understanding the processes that develop and maintain diversity in coastal communities is an important challenge, particularly given the conservation and management needs of these ecosystems. Such diversity patterns include not only species distributions and interactions, but also variation in genetic diversity. Alongshore variations in allele frequency along coastal oceans are controlled by interactions between physical and biological forces. Here we model these interactions in terms of Lagrangian descriptors of nearshore physical oceanography, the life history dynamics of an individual species and habitat quality. This model allows us to define population boundaries within the species range as a function of ocean circulation, spatial habitat variability and larval characteristics. From this, we can find quantitative criteria for the persistence of regions of alongshore genetic variation. Our results show quantitatively that the existence of phylogeographic patterns in species with high dispersal capacity along uniform coasts with typical mean currents is surprising, and requires either strong selection gradients, alongshore variation in ocean currents and/or habitat quality, or a mixture of both. Our model suggests that marine reserves and the harvesting of marine recources can dramatically modify spatial gradients in genetic diversity. © Inter-Research 2007.