Data from: Contrasting patterns of genome-wide polymorphism in the native and invasive range of the marine mollusk Crepidula fornicata

Selection processes are believed to be an important evolutionary driver behind the successful establishment of non-indigenous species, however evidence is still scarce. Genome-scans have often identified loci with atypical patterns of genetic differentiation (i.e. outliers) indicative of selection processes. Using microsatellite- and AFLP-based genome-scans, we looked for evidence of post-introduction selection in the mollusk Crepidula fornicata, native from the northwestern Atlantic and introduced in the northeastern Atlantic and northeastern Pacific during the 19th and 20th centuries. We examined 683 individuals from 7 native and 15 introduced populations spanning the latitudinal introduction and native ranges of the species. Our results showed the high genetic diversity in all populations with little genetic structure between the two ranges, a pattern typical of marine invaders. Analyzing 344 loci, no outliers were detected between introduced and native populations or within introduced populations. The genomic sampling may have been insufficient to reveal selection especially if it acts on traits determined by a few genes. Eight outliers were however identified within the native range, underlining a genetic singularity congruent with a well-known biogeographic break along the Florida. Our results call into question the relevance of AFLP genome-scans in detecting adaptation on the time-scale of biological invasions: genome-scans often reveal long-term adaptation involving numerous genes throughout the genome but seem less effective in detecting recent adaptation from pre-existing variation on polygenic traits. This study advocates other methods to detect selection effects during biological invasions – on phenotypic traits, although genome-scans may remain useful for elucidating introduction histories