Modeling local adaptation and gene flow in sockeye salmon
Authored by Lorenz Hauser, Jeffrey J Hard, Ray Hilborn, Jocelyn E Lin
Date Published: 2017
DOI: 10.1002/ecs2.2039
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Abstract
Microevolutionary processes determine levels of local adaptation within
populations and presumably affect population productivity, but selection
and phenotypic evolution have not often been linked explicitly to
population dynamics in the wild. Here, we describe a stochastic,
individual-based model that simulates evolutionary and demographic
effects of migration and selection in interconnected sockeye salmon
populations. Two populations were simulated based on parameters obtained
empirically from wild populations in the Bristol Bay region of
southwestern Alaska, representing beach-and stream-spawning ecotypes.
Individuals underwent a full salmonid life cycle, experiencing sexual
selection, size-selective harvest, and predation based on body size at
maturity. Stabilizing natural selection on the three traits (body
length, body depth, and age at maturity) tracked for all individuals
favored different phenotypes in the two ecotype populations, and the
three traits evolved in a genetically correlated manner. Simulation
results showed that stabilizing selection on fish phenotypes was always
critical for maintaining local adaptation, especially when dispersal
rates were high, but loss of local adaptation did not result in
substantial loss of productivity. Rather, productivity was more strongly
influenced by the opposing effects of stabilizing and harvest selection;
strong stabilizing selection caused the salmon to evolve larger body
sizes that made them more likely to be caught in the fishery. The model
results suggest that interactions between different selection pressures
can have substantial demographic as well as evolutionary consequences in
wild salmon populations, with key implications for sustainability of
natural production in the face of selective harvest and systemic
environmental change.
Tags
Individual-based model
Population dynamics
Natural selection
Population-dynamics
Body-size
Gene flow
G-matrix
Oncorhynchus-nerka
Local
adaptation
Quantitative genetics
Induced evolution
Contemporary evolution
Human-induced evolution
Bears ursus-arctos
Brown bears
Correlated characters