Résumé
Genetic diversity is crucial for species’ maintenance and persistence, yet
is often overlooked in conservation studies. Species diversity is more
often reported due to practical constraints, but it is unknown if these
measures of diversity are correlated. In marine invertebrates, adults are
often sessile or sedentary and populations exchange genes via dispersal of
gametes and larvae. Species with a larval period are expected to have more
connected populations than those without larval dispersal. We assessed the
relationship between measures of species and genetic diversity, and
between dispersal ability and connectivity. We compiled data on genetic
patterns and life history traits in nine species across five phyla.
Sampling sites spanned 600 km in the northwest Mediterranean Sea and
focused on a 50 km area near Marseilles, France. Comparative population
genetic approaches yielded three main results. (1) Species without larvae
showed higher levels of genetic structure than species with free-living
larvae but the role of larval type (lecithotrophic or planktotrophic) was
negligible. (2) A narrow area around Marseilles, subject to offshore
advection, limited genetic connectivity in most species. (3) We identified
sites with significant positive contributions to overall genetic diversity
across all species, corresponding with areas near low human population
densities. In contrast, high levels of human activity corresponded with a
negative contribution to overall genetic diversity. Genetic diversity
within species was positively and significantly linearly related with
local species diversity. Our study suggests that local contribution to
overall genetic diversity should be taken into account for future
conservation strategies.