Towards predictive models of genetic differentiation and diversity for the delineation and prioritization of conservation units of the grey reef shark (<i>Carcharhinus amblyrhynchos</i>)

Abstract

<p>Ensuring a species long term persistence requires to preserve its evolutionary potential (its ability to face future change), which is proportional to its genetic diversity. An assessment of genetic structure and diversity across a species range is therefore needed to delineate and prioritize conservation units. Mapping genetic diversity and structure across all subpopulations of a species, however, may be logistically and economically unfeasible.\nUsing the endangered grey reef shark (<i>Carcharhinus amblyrhynchos</i>) as a model system, we develop a framework to delineate and prioritize conservation units from limited genetic data. We map genetic diversity and reconstruct the species demographic history based on genetic data from 515 grey reef sharks sampled across the species range. We then apply a framework based on circuit theory to create predictive models of genetic differentiation that explains 98 % of observed variation in genetic differentiation, and use this predictive model delineate conservation units across the species range using arbitrary thresholds of FST. We identify the major limitation of this approach when applied to populations not at migration-drift equilibrium (the assumed relationship between FST and gene flow), and propose a solution based on direct estimates of gene flow using demographic models.\nFinally, using realistic simulations and empirical data, we delineate a framework to predict genetic diversity and prioritize conservation units to maximize evolutionary potential. This framework is broadly applicable, takes into account how demographic history shapes genetic diversity, does not assume migration-drift equilibrium and only requires sparse genetic data across a species range<br></p>