Potential and realized connectivity of the seagrass Posidonia oceanica and their implication for conservation

Genetic assignment methods use genotype likelihoods to draw inference about where individuals were or were not born, potentially allowing direct, real-time estimates of dispersal. We used simulated data sets to test the power and accuracy of Monte Carlo resampling methods in generating statistical thresholds for identifying F0 immigrants in populations with ongoing gene flow, and hence for providing direct, real-time estimates of migration rates. The identification of accurate critical values required that resampling methods preserved the linkage disequilibrium deriving from recent generations of immigrants and reflected the sampling variance present in the data set being analysed. A novel Monte Carlo resampling method taking into account these aspects was proposed and its efficiency was evaluated. Power and error were relatively insensitive to the frequency assumed for missing alleles. Power to identify F0 immigrants was improved by using large sample size (up to about 50 individuals) and by sampling all populations from which migrants may have originated. A combination of plotting genotype likelihoods and calculating mean genotype likelihood ratios (DLR) appeared to be an effective way to predict whether F0 immigrants could be identified for a particular pair of populations using a given set of markers.

Although 71% of marine protected areas are benefiting fish populations, their effects are highly variable, with staff capacity proving to be the most important explanatory variable.

Local adaptation in the sea was regarded historically as a rare phenomenon that was limited to a handful of species with exceptionally low dispersal potential. However, a growing body of experimental studies indicates that adaptive differentiation occurs in numerous marine invertebrates in response to selection imposed by strong gradients (and more complex mosaics) of abiotic and biotic conditions. Moreover, a surprisingly high proportion of the marine invertebrates known or suspected of exhibiting local adaptation are species with planktonic dispersal. Adaptive divergence among populations can occur over a range of spatial scales, including those that are fine-grained (i.e., meters to kilometers), reflecting a balance between scales of gene flow and selection. Addressing the causes and consequences of adaptive genetic differentiation among invertebrate populations promises to advance community ecology, climate change research, and the effective management of marine ecosystems.