Founding events influence genetic population structure of sockeye salmon (Oncorhynchus nerka) in Lake Clark, Alaska

Abstract

Bottlenecks can have lasting effects on genetic population structure that obscure patterns of contemporary gene flow and drift. Sockeye salmon are vulnerable to bottleneck effects because they are a highly structured species with excellent colonizing abilities and often occupy geologically young habitats. We describe genetic divergence among and genetic variation within spawning populations of sockeye salmon throughout the Lake Clark area of Alaska. Fin tissue was collected from sockeye salmon representing 15 spawning populations of Lake Clark, Six-mile Lake, and Lake Iliamna. Allele frequencies differed significantly at 11 microsatellite loci in 96 of 105 pairwise population comparisons. Pairwise estimates of FST ranged from zero to 0.089. Six-mile Lake and Lake Clark populations have historically been grouped together for management purposes and are geographically proximate. However, Six-mile Lake populations are genetically similar to Lake Iliamna populations and are divergent from Lake Clark populations. The reduced allelic diversity and strong divergence of Lake Clark populations relative to Six-mile Lake and Lake Iliamna populations suggest a bottleneck associated with the colonization of Lake Clark by sockeye salmon. Geographic distance and spawning habitat differences apparently do not contribute to isolation and divergence among populations. However, temporal isolation based on spawning time and founder effects associated with ongoing glacial retreat and colonization of new spawning habitats contribute to the genetic population structure of Lake Clark sockeye salmon. Nonequilibrium conditions and the strong influence of genetic drift caution against using estimates of divergence to estimate gene flow among populations of Lake Clark sockeye salmon.

Changes in Mating System and Social Structure of the Ant Petalomyrmex Phylax Are Associated With Range Expansion in Cameroon

“…Signatures for bottlenecks are extremely transient (Cornuet and Luikart 1996;Luikart et al 1998;Piry et al 1999). Accordingly, ancient variations in population size could result in relatively moderate changes in the distribution of allele frequencies, as observed between groups P and M (for similar results, see Ramstad et al 2004). …”

Molecular identification of livestock breeds: a tool for modern conservation biology

“…The factors that are responsible for the erosion of genetic diversity are often a function of the size of the population under consideration (Barbato, Orozco-terWengel, Tapio et al, 2015). Generally, the smaller a livestock population, the greater is its vulnerability to extinction (Biscarini, Nicolazzi, Stella et al, 2015;Henson, 1992;Ramstad, Woody, Sage et al, 2004). Human factors offer the greatest threat to global livestock diversity (Biscarini et al, 2015;Frankham, 1995).…”

“…The impact of a bottleneck is logically more profound on small breeding populations because the originally available pool of genetic diversity is smaller, and is hence more severely depleted in fewer generations. In population genetic studies a bottleneck effect is referred to as a founder effect if it is associated with the founding of a new population (Dlugosch & Parker, 2008;Ramstad et al, 2004;Templeton, 1980). Random events such as founder and bottleneck effects that imperfectly eliminate genes and reduce variability within a population are described as genetic drift (Newman & Pilson, 1997;Ramstad et al, 2004).…”

“…In population genetic studies a bottleneck effect is referred to as a founder effect if it is associated with the founding of a new population (Dlugosch & Parker, 2008;Ramstad et al, 2004;Templeton, 1980). Random events such as founder and bottleneck effects that imperfectly eliminate genes and reduce variability within a population are described as genetic drift (Newman & Pilson, 1997;Ramstad et al, 2004). Reduction in heterozygosity in a livestock population can be associated with decline in fitness of individual members, as is often the case in wild populations (Worley, Collet, Spurgin et al, 2010).…”

Importance and future of individual markers for the ecosystem approach to fisheries

“…Besides this general feature, effective population size allows following population dynamics (as it was done with salmon populations, see Waples 2002) and identifying events, such as population bottlenecks (i.e. drastic reduction in genetic variability generally related to strong population decline), as exemplified in lake trout and sockeye salmon (see Guinand and Scribner 2003;Ramstad et al 2004). Effective population size, when estimated on a regular basis, could also be applied in stock assessment and management procedures as a complementary indicator to spawning stock biomass (Waples 2002;Waples et al 2008).…”