Genetic Population Structure and Origin of Life History Types in Chinook Salmon in British Columbia, Canada

Abstract

We used protein electrophoresis to examine genetic population structure and origin of life history types of chinook salmon Oncorhynchus tshawytscha in British Columbia, Canada. Among 31 allozyme loci resolved in 91 samples from 63 populations of chinook salmon in rivers and hatcheries throughout British Columbia, population heterozygosities averaged 0.084 (range 0.048–0.108) and were typical of values for populations in other regions. A hierarchical gene diversity analysis indicated that 91.3% of the total allele‐frequency diversity was attributable to within‐population variability; the remaining 8.7% was attributable to geographic variability among populations, which was partitioned into among‐river (3.3%), among‐area (3.5%), and among‐region (1.9%) components. Two major groups of populations appeared in the principal components analysis and in cluster analysis of genetic distances. A coastal group included populations in four subgroups: Central coast, Georgia Strait, lower Fraser River, and west Vancouver Island. An inland group included six subgroups: Nass River, Skeena River, north Thompson River, upper and mid‐Fraser River, south Thompson River, and lower Thompson River. The geographic extents of the inland and coastal groups largely coincided with the geographic distributions of stream‐ and ocean‐type juvenile forms and may reflect postglacial colonization by two ancestral lineages that survived in Pleistocene refugia. The presence of genetically undifferentiated stream‐type fish in coastal streams populated by ocean‐type fish may reflect either postglacial life history differentiation from ancestral ocean‐type fish or life history flexibility of ocean‐type fish.

Life-History Divergence in Chinook Salmon: Historic Contingency and Parallel Evolution

“…(A complete set of allelic frequencies can be retrieved by accessing the website http:// www.nwfsc.noaa.gov/publications/). The genotypic frequencies for these samples generally conform to Hardy-Weinberg expectations (Utter et al 1989;Bartley et al 1992;Waples et al 1993;Teel et al 2000), and the banding patterns conform to expectations based on subunit structure of the enzymes, indicating that the data generally meet the criteria Utter et al (1987) suggested for inferring a genetic basis for phenotypic variation of allozymes. In Chinook salmon, the duplicated loci sAAT-1,2*, sMDH-A1,2*, and sMDH-B1,2* are considered isoloci (Waples 1988).…”

“…However, on a broader geographic scale it is apparent that the pattern of genetic/life-history relationships in Chinook salmon is more complicated than proposed by Healey or in other recent studies with a more restricted geographic scope (e.g., Teel et al 2000). First, the extremely divergent upper Willamette River populations suggest that Healey's hypothesis of only two major lineages may be too simplistic.…”

“…Collection dates spanned the years 1981-2000, although the majority of samples were collected from the mid-1980s to the mid-1990s (a period covering about two to three salmon generations). Previous studies (Utter et al 1989;Waples and Teel 1990;Teel et al 2000) have shown that the major features of Chinook salmon population genetic structure are stable over these time periods.Allele frequency data for 77 of the populations have been 389 CHINOOK SALMON LIFE-HISTORY EVOLUTION previously published (see Appendix 1). Additional data for many of those populations and data for the remaining populations are unpublished.…”

Annual coastal migration of juvenile Chinook salmon: static stock-specific patterns in a highly dynamic ocean

“…Yearling type smolts predominate in the North (north of 56°N), whereas sub-yearling smolts are almost exclusively distributed in the South (Healey 1991). The main exceptions are the Fraser and the Columbia River systems, as well as populations in northern Puget Sound where both types are found (Healey 1991, Teel et al 2000, Waples et al 2004.…”

“…Yearling type smolts predominate in the North (north of 56°N), whereas sub-yearling smolts are almost exclusively distributed in the South (Healey 1991). The main exceptions are the Fraser and the Columbia River systems, as well as populations in northern Puget Sound where both types are found (Healey 1991, Teel et al 2000, Waples et al 2004.Recent studies have focused both on defining marine habitat use for juvenile Chinook salmon (Bi et al 2007, 2008, 2011a, Peterson et al 2010 and the relationship between variable ocean conditions and abundance, growth or condition (Wells et al 2008, MacFarlane 2010. The presence and abundance of Chinook salmon is negatively correlated with water temperature and depth, and positively correlated to various production indices such as chlorophyll (chl) a concentration and zooplankton (copepod) biomass (Brodeur et al 2000, Fisher et al 2007, Bi et al 2007, 2011a, Peterson et al 2010.…”