Nested analysis of genetic diversity in northwestern North American char,Dolly Varden (Salvelinus malma) and bull trout (Salvelinus confluentus)

摘要

Partitioning within-species genetic diversity is fundamental to conservation of the bioheritage, current viability, and evolutionary potential of individual taxa. We conducted a hierarchical analysis of genetic diversity in Dolly Varden (Salvelinus malma) and bull trout (Salvelinus confluentus) involving analysis of hybrid zones between Dolly Varden and bull trout, analysis of phylogenetic structure within species across their native ranges using mitochondrial DNA, and a microsatellite DNA survey of population subdivision of bull trout within single watersheds. Our analyses documented hybridization and some introgression between Dolly Varden and bull trout across a geographically widespread zone of secondary contact between the two species. Both species were subdivided into two major mtDNA lineages, and one lineage in Dolly Varden may have arisen through introgression with bull trout. Bull trout have low levels of microsatellite diversity within populations, but there was substantial interpopulation variation in allele frequencies. Allele frequency distributions suggested that recent, severe bottlenecks occur frequently in bull trout populations. Our results illustrate partitioning of genetic variation at distinct levels of biological organization (species, phylogeographic lineages, local populations), and we address how such nested variation is fundamental to conservation of biodiversity.