Data from: Neither philopatric nor panmictic: microsatellite and mtDNA evidence suggests lack of natal homing but limits to dispersal in Pacific lamprey

Most species with lengthy migrations display some degree of natal homing; some (e.g., migratory birds and anadromous salmonids) show spectacular feats of homing. However, studies of the sea lamprey (Petromyzon marinus) indicate that this anadromous species locates spawning habitat based on pheromonal cues from larvae rather than through philopatry. Previous genetic studies in the anadromous Pacific lamprey (Entosphenus tridentatus) have both supported and rejected the hypothesis of natal homing. To resolve this, we used nine microsatellite loci to examine population structure in 965 Pacific lamprey from 20 locations from central British Columbia to southern California, and supplemented this analysis with mitochondrial DNA restriction fragment length polymorphism analysis on a subset of 530 lamprey. Microsatellite analysis revealed: 1) relatively low but often statistically significant genetic differentiation among locations (97% pairwise FST values were less than 0.04 but 73.7% were significant); and 2) weak but significant isolation-by-distance (r2 = 0.0565, P = 0.0450) but no geographic clustering of samples. The few moderate FST values involved comparisons with sites that were geographically distant or far upstream. The mtDNA analysis—although providing less resolution among sites (only 4.7% FST values were significant)—was broadly consistent with the microsatellite results: 1) the southernmost site and some sites tributary to the Salish Sea were genetically distinct; and 2) southern sites showed higher haplotype and private haplotype richness. These results are inconsistent with philopatry, suggesting that anadromous lampreys are unusual among species with long migrations, but suggest that limited dispersal at sea precludes panmixia in this species.Microsatellite allele sizes of Pacific lamprey from 20 locations along the west coast of North AmericaMicrosatellite allele sizes determined using Genemapper, formatted for Genepop.Genepop.txtList of haplotypes and composite haplotypes for Pacific lamprey collected from 20 locations along the west coast of North AmericaRFLP haplotypes determined by gel electrophoresisRFLP results.tx