Signatures of selection A Z-transformed haplotype-based FST' (zFst') estimates for loci (dots) across all chromosomes (noted on the x-axis). Outlier loci with zFST' ≥ 3 are shown in orange B absolute divergence (Dxy') between outlier loci (orange) and the genomic background on autosomes and the sex chromosome. Individual dots denote genomic loci and the distribution of values is shown by density plots. The sex chromosome was analysed separately due to lower recombination rates compared to autosomes and, therefore, potentially higher absolute divergence C comparison of delta gene diversity (∆Hs) between the genomic background (zFst' < 3; grey), outlier loci (orange) and outlier loci showing increased absolute divergence (zDxy' ≥ 3; red). Delta gene diversity was estimated by subtracting gene diversity in pelagic individuals from gene diversity in littoral individuals. Positive ∆Hs values are indicative of reduced gene diversity in littoral individuals and vice versa. Individual dots denote genomic loci. Box plots defined in Fig. 2B.