title: Recurrent evolution of life history ecotypes in sockeye salmon: implications for conservation and future evolution.
abstract: We examine the evolutionary history and speculate about the evolutionary future of three basic life history ecotypes that contribute to the biocomplexity of sockeye salmon (Oncorhynchus nerka). The 'recurrent evolution' (RE) hypothesis claims that the sea/river ecotype is ancestral, a 'straying' form with poorly differentiated (meta)population structure, and that highly structured populations of lake-type sockeye and kokanee have evolved repeatedly in parallel adaptive radiations between recurrent glaciations of the Pleistocene Epoch. Basic premises of this hypothesis are consistent with new, independent evidence from recent surveys of genetic variation in mitochondrial and microsatellite DNA: (1) sockeye salmon are most closely related to pink (O. gorbuscha) and chum (O. keta) salmon with sea-type life histories; (2) the sockeye life history ecotypes exist as polyphyletic lineages within large drainages and geographic regions; (3) the sea/river ecotype exhibits less genetic differentiation among populations than the lake or kokanee ecotypes both within and among drainages; and (4) genetic diversity is typically higher in the sea/river ecotype than in the lake and kokanee ecotypes. Anthropogenic modification of estuarine habitat and intensive coastal fisheries have likely reduced and fragmented historic metapopulations of the sea/river ecotype, particularly in southern areas. In contrast, the kokanee ecotype appears to be favoured by marine fisheries and predicted changes in climate.
authors.affiliation: Fisheries and Oceans Canada, Pacific Biological Station Nanaimo, British Columbia, Canada V9T 6N7.
authors.forename: Chris C
authors.initials: CC
authors.lastname: Wood
authors.affiliation: Department of Forestry and Natural Resources, Purdue University 195 Marstellar Street, West Lafayette, Indiana, 47907, USA.
authors.forename: John W
authors.initials: JW
authors.lastname: Bickham
authors.affiliation: University of Victoria, Department of Biology-Centre for Biomedical Research Post Office Box 3020, Victoria, British Columbia Canada V8W 3N5.
authors.forename: R
authors.initials: R
authors.lastname: John Nelson
authors.affiliation: Malaspinia University-College 900 5th Street, Nanaimo, British Columbia, Canada V9R 5S5.
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Foote
authors.affiliation: Department of Forestry and Natural Resources, Purdue University 195 Marstellar Street, West Lafayette, Indiana, 47907, USA.
authors.forename: John C
authors.initials: JC
authors.lastname: Patton
keywords: biocomplexity; conservation value; ecotype; kokanee; lake-type; niche model; recurrent evolution; river-type; sea-type