Data from: Genetic differentiation but no reduction in genetic diversity at the northern range edge of two species with different dispersal modes

Theory predicts that genetic variation should be reduced at range margins, but empirical support is equivocal. Here, we used genotyping-by-sequencing technology to investigate genetic variation in central and marginal populations of two species in the marine gastropod genus Crepidula. These two species have different development and dispersal types, and might therefore show different spatial patterns of genetic variation. Both allelic richness and the proportion of private alleles were highest in the most central populations of both species, and lower at the margin. The species with low dispersal, C. convexa, showed high degrees of structure throughout the range that conform to the pattern found in previous studies using other molecular markers. The northernmost populations of the high-dispersing species, C. fornicata, are distinct from more central populations, though this species has been previously observed to have little genetic structure over much of its range. Although genetic diversity was significantly lower at the range margin, the absolute reduction in diversity observed with these genome-wide markers was slight, and it is not yet known if there are functional consequences for these marginal populations.mergedSNPsSampling coordinates and site codesThis file lists all sampling sites, with their associated GPS coordinates. It gives the letter and number abbreviations for the main text and all analysis files.bayescan_input_fornicataInput file for Bayescan for Crepidula fornicata.bayescan_input_convexaInput file for Bayescan with Crepidula convexa data.bayescan_output_fornicataOutput from Bayescan analysis from Crepidula fornicata.bayescan_output_convexaOutput from Bayescan analysis for Crepidula convexapairwise_distance_matricesMatrices of pairwise genetic (Fst) and geographic (in kilometers) distances for populations of Crepidula fornicata and C. convexa.input_hierfstat_fornicataThis file is the input file for Hierfstat for Crepidula fornicata. It was used for both Hierfstat and Adegenet analyses.input_hierfstat_convexaThis file was used as input for the Hierfstat package in R, and downstream analyses in Adegenet, for Crepidula convexa.filtered_SNPs_convexaFiltered SNP dataset for Crepidula convexa. Filtering was done as described in the main text. SNPs are reported using the IUPAC codes.filtered_SNPs_fornicataFiltered SNP dataset for Crepidula fornicata. Filtering was done as described in the main manuscript text. SNPs are reported using IUPAC codes