Population genetic data for freshwater mussels: <em>Unio crassus</em> and <em>Unio nanus</em> in Europe

Historically, the thick-shelled river mussel (Unio crassus agg. complex) was considered a single, widespread species across Europe. However, recent phylogenetic taxonomic revisions have delineated 12 species from this complex, including Unio crassus (s. str. Philipsson in Retzius, 1788), Unio nanus (Lamarck, 1819 stat. rev.), which exhibit substantial range overlap and broad European distributions. Understanding their fine-scale genetic diversity, population structure, and potential for recent or ancient hybridization is critical for effective conservation planning. This study investigated the genetic diversity and structure of U. crassus and U. nanus across Europe, examining the influence of glacial disturbance history and host fish associations. Using mitochondrial (COI) and nuclear (microsatellite) markers on 60 populations, we revealed a discordance between mitochondrial and nuclear structuring, suggesting ancient introgression. Crucially, no evidence of recent hybridization was det..., , # Population genetic data for freshwater mussels: *Unio crassus* and *Unio nanus* in Europe ## 1. Dataset Overview This dataset contains raw and processed genetic data used in the study investigating the population structure, genetic diversity, and evolutionary history of two European freshwater mussel species, *Unio crassus* (the thick-shelled river mussel) and *Unio nanus*. The data comprises mitochondrial cytochrome c oxidase subunit I (COI) sequences and nuclear microsatellite genotypes. This research aims to understand historical gene flow, identify instances of ancient introgression, and provide insights for conservation management of these often threatened species across their European ranges. ## 2. Data Files This directory contains the primary genetic data files. * `1_Individual_Microsatellite_Data.xlsx`: Excel table containing raw microsatellite genotypes for all individuals across all loci. * `2_Individual_Sequence_Data.fas`: FASTA file containing all aligned mitochondri...,