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Habitat continuity and geographic distance predict population genetic differentiation in giant kelp

by Alberto F, Raimondi PT, Reed DC, Coelho NC, Leblois R, Whitmer A, Serrão EA
Ecology 91 (2010), pp. 49-56
Output type: publication
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Isolation by distance (IBD) models are widely used to predict levels of genetic connectivity as a function of Euclidean distance, and although recent studies have used GIS-landscape ecological approaches to improve the predictability of spatial genetic structure, few if any have addressed the effect of population size and habitat continuity on gene flow. Landscape effects on genetic connectivity are even less understood in marine populations, where habitat mapping is particularly challenging. In this study, we model spatial genetic structure of a habitat-structuring species, the giant kelp Macrocystis pyrifera, using highly variable microsatellite markers. GIS mapping was used to characterize habitat continuity and distance between sampling sites along the mainland coast of the Santa Barbara Channel, and their roles as predictors of genetic differentiation were evaluated. Connectivity (σ) and Ne were estimated by comparing our IBD slope with those from simulations incorporating the habitat continuity. We found the highest allelic richness yet reported for macroalgae, (7 to 50 alleles×locus-1). The best regression model relating genetic distance to habitat variables included both geographic distance and habitat continuity, which were respectively, positively and negatively related to genetic distance. Our results provide strong support for a dependence of gene flow on both distance and habitat continuity. Our estimates of connectivity among populations were consistent with previous estimates obtained using empirical and theoretical approaches.