Reconciling direct and indirect estimates of functional connectivity in a Mediterranean pond-breeding amphibian

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Understanding demographic dynamics and functional connectivity among demes is essential to prevent, identify and reverse amphibian population declines. Attempts to characterize connectivity among amphibian populations have largely relied on the use of molecular markers to assess patterns of genetic structure at the landscape scale and identify factors that promote or restrict gene flow. However, few studies have integrated population size estimates and direct records of dispersal rates (e.g. based on capture-mark-recapture data) to help interpret molecular-based inferences. We conducted such an integrative, long-term monitoring program of a metapopulation of the sharp-ribbed newt (Pleurodeles waltl), a pond-breeding salamander endemic to the Iberian Peninsula and North Africa. Over 12 breeding seasons, we compiled individual capture histories to estimate population sizes and document patterns of dispersal, and inferred migration rates and pairwise relatedness based on 22 microsatellite loci. Direct (based on capture-mark-recapture) estimates revealed low levels of contemporary dispersal between the two major breeding sites in the study area, whereas indirect (molecular) estimates provided evidence for asymmetric gene flow, more intense from the larger to the smaller population, without consistent differences between sexes. Direct and indirect estimates can be reconciled based on the species’ generation time, and support a scenario of density-dependent dispersal, with recent colonization of the smaller pond inferred from differences in the relative proportions of ancestry categories across ponds. Our integrative approach can be applied to design conservation actions aiming to improve functional connectivity among amphibian populations based on empirical evidence.