Allozyme analyses
The results of our allozyme analyses closely mirrored those obtained for the SNPs dataset, both in terms of primary genetic lineages and identifying pure versus admixed populations. A series of PCoA analyses of the allozyme data (Fig. 4) displayed a near-identical association between individuals as depicted for the SNPs (Fig. 2), and together supported the presence of the same seven primary groupings, namely KN, pure KE, KEm (close to pure KE but slightly displaced towards KS), KSxKE, pure KS, KWm, and pure KW. The same assignment of sites into primary groupings is shown in an unrooted NJ tree (Fig. 5). These findings are further validated by the fixed difference and observed heterozygosity counts for each grouping (Table 3), which show the same patterns of diagnosability and comparative levels of heterozygosity as found for the SNPs. Together our two nuclear datasets fully support the presence of four primary taxa in the western carp gudgeon, namely KN, KE+ (KE+KEm), KS, and KW+ (KW+KWm), all readily diagnosable by numerous SNP and allozyme loci (Table 4).