Data accessibility: Sequence data generated and analyzed during the current study have been deposited at the European Nucleotide Archive (http://www.ebi.ac.uk/ena) under the accession PRJEB56839.
Author contributions: XY and PAH conceived the study, PAH collected the field material, XY performed the lab work and the bioinformatic analysis with guidance of TS and CWW, XY wrote the first draft and all authors provided comments on the manuscript.
Table 1. Summary results from the HDMKPRF test among three beetle species. Table shows the number of synonymous/ nonsynonymous sites variable among (Ds, Dn ) and within (Ps, Pn ) species summed across all 4154 single copy orthologs. The proportion of nonsynoymous sites fixed by positive selection (α = 1-DsPn/DnPs ), and the proportion of genes under positive and negative selection estimated by HDMKPRF, for G. calmariensis , G. pusilla andG. tenella . Summary statistics were calculated before and after singleton removal. Counts are for synonymous and non-synonymous sites divergent between (Ds andDn , respectively) and polymorphic within (Ps, Pn , respectively) species.