Résumé
Genetic variation, as a basis of evolutionary change, allows species to
adapt and persist in different climates and environments. Yet, a
comprehensive assessment of the drivers of genetic variation at different
spatial scales is still missing in marine ecosystems. Here, we
investigated the influence of environment, geographic isolation, and
larval dispersal on the variation in allele frequencies, using an
extensive spatial sampling (47 locations) of the striped red mullet
(Mullus surmuletus) in the Mediterranean Sea. Univariate multiple
regressions were used to test the influence of environment (salinity and
temperature), geographic isolation, and larval dispersal on Single
Nucleotide Polymorphisms (SNPs) allele frequencies. We used Moran’s
Eigenvector Maps (db-MEMs) and Asymmetric Eigenvector Maps (AEMs) to
decompose geographic and dispersal distances in predictors representing
different spatial scales. We found that salinity and temperature had only
a weak effect on the variation in allele frequencies. Our results revealed
the predominance of geographic isolation to explain variation in allele
frequencies at large spatial scale (> 1,000km) while larval
dispersal was the major predictor at smaller spatial scale (<
1,000km). Our findings stress the importance of including spatial scales
to understand the drivers of spatial genetic variation. We suggest that
larval dispersal allows to maintain gene flows at small to intermediate
scale, while at broad scale, genetic variation may be mostly shaped by
adult mobility, demographic history or multi-generational stepping stone
dispersal. These findings bring out important spatial scale considerations
to account for in the design of a protected areas network that would
efficiently enhance protection and persistence capacity of marine species.