Abstract
Genetic diversity and divergence patterns of smallmouth bass Micropterus dolomieu spawning groups are analysed across its northern native range with mtDNA cytochrome b gene sequences and eight unlinked nuclear DNA microsatellite loci. Results reveal high levels of genetic variability and significant differences in allelic representation among populations ( mtDNA : mean ± s.e ., H D = 0·50 ± 0·06, mean ± s.e ., θ ST = 0·41 ± 0·02 and microsatellites: mean ± s.e . H O = 0·46 ± 0·03, mean ± s.e . θ ST = 0·25 ± 0·01). The distributions of 28 variant mtDNA haplotypes, which differ by an average of 3·94 nucleotides (range = 1–8), denote divergent representation among geographic areas. Microsatellite data support nine primary population groups, whose high self‐assignment probabilities likewise display marked divergence. Genetic patterns demonstrate: (1) high genetic diversity in both genomes, (2) significant divergence among populations, probably resulting from natal site homing and low lifetime migration, (3) support for three post‐glacial refugia that variously contributed to the current northern populations, which remain evident today despite waterway connectivity and (4) a weak yet significant genetic isolation by geographic distance pattern, indicating that other processes affect the differences among populations, such as territoriality and site fidelity.