title: Population size is weakly related to quantitative genetic variation and trait differentiation in a stream fish.
abstract: How population size influences quantitative genetic variation and differentiation among natural, fragmented populations remains unresolved. Small, isolated populations might occupy poor quality habitats and lose genetic variation more rapidly due to genetic drift than large populations. Genetic drift might furthermore overcome selection as population size decreases. Collectively, this might result in directional changes in additive genetic variation (VA ) and trait differentiation (QST ) from small to large population size. Alternatively, small populations might exhibit larger variation in VA and QST if habitat fragmentation increases variability in habitat types. We explored these alternatives by investigating VA and QST using nine fragmented populations of brook trout varying 50-fold in census size N (179-8416) and 10-fold in effective number of breeders, Nb (18-135). Across 15 traits, no evidence was found for consistent differences in VA and QST with population size and almost no evidence for increased variability of VA or QST estimates at small population size. This suggests that (i) small populations of some species may retain adaptive potential according to commonly adopted quantitative genetic measures and (ii) populations of varying sizes experience a variety of environmental conditions in nature, however extremely large studies are likely required before any firm conclusions can be made.
authors.affiliation: Department of Biology, Concordia University, Montreal, QC, H4B 2E5, Canada. jackiewood7@gmail.com.|Group for interuniversity research in limnology and aquatic environment (GRIL), Université du Québec à Trois-Rivières, Trois-Rivières, QC, G9A 5H7, Canada. jackiewood7@gmail.com.
authors.forename: Jacquelyn L A
authors.initials: JL
authors.lastname: Wood
authors.affiliation: Department of Biology, Concordia University, Montreal, QC, H4B 2E5, Canada.
authors.forename: Defne
authors.initials: D
authors.lastname: Tezel
authors.affiliation: Department of Biology, Concordia University, Montreal, QC, H4B 2E5, Canada.
authors.forename: Destin
authors.initials: D
authors.lastname: Joyal
authors.affiliation: Department of Biology, Concordia University, Montreal, QC, H4B 2E5, Canada.|Group for interuniversity research in limnology and aquatic environment (GRIL), Université du Québec à Trois-Rivières, Trois-Rivières, QC, G9A 5H7, Canada.
authors.forename: Dylan J
authors.initials: DJ
authors.lastname: Fraser
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D049628:Body Size / Q000235:genetics; D017753:Ecosystem; D040961:Genetic Drift; D005828:Genetics, Population; D008018:Life Cycle Stages / Q000235:genetics; D009523:Newfoundland and Labrador; D011156:Population Density; D045483:Rivers; D012641:Selection, Genetic; D014337:Trout / Q000033:anatomy & histology / Q000235:genetics*
keywords: Additive genetic variation; QST; adaptive potential; effective population size; habitat fragmentation; salmonid