Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8716
Title: Human-mediated evolution in a threatened species? Juvenile life-history changes in Snake River salmon
Author: Robin S. Waples, A. Elz, B. D. Arnsberg, James R. Faulkner, Jeffrey J. Hard, Emma Timmins-Schiffmann, Linda K. Park
Publication Year: 2017
Journal: Evolutionary Applications
Volume: 10
Pages: 667-681
DOI: 10.1111/eva.12468

It is widely recognized that the human footprint is large in all of Earth¿s ecosystems, but evaluations of the consequences of this reality often ignore evolutionary changes in response to altered selective regimes.  Habitats for Snake River fall Chinook salmon (SRFCS), a threatened species in the U.S., have been dramatically changed by hydropower development.  Associated biological changes include a shift in juvenile life history: historically ~100% of juveniles migrated to sea as subyearlings, but a substantial fraction have migrated as yearlings in recent years.  In contemplating future management actions for this species should major Snake River dams ever be removed (as many have proposed), it will be important to understand whether evolution is at least partially responsible for this life-history change.  We hypothesized that if this trait is genetically based, parents who migrated to sea as subyearlings should produce faster-growing offspring that would be more likely to reach a size threshold to migrate to sea in their first year.  We tested this with phenotypic data for >2600 juvenile SRFCS that were genetically matched to parents.  Three lines of evidence supported our hypothesis: 1) the animal model estimated substantial heritabilities for juvenile growth rate for three consecutive cohorts; 2) linear modeling showed an association between juvenile life history of parents and offspring growth rate; and 3) faster-growing juveniles migrated faster, as expected if they were more likely to be heading to sea.  Surprisingly, we also found that parents reared a full year in a hatchery produced the fastest-growing offspring of all¿apparently an example of cross-generational plasticity associated with artificial propagation.  We suggest that SRFCS is an example of a potentially much larger class of conservation-reliant species that can also be considered to be ¿anthro-evolutionary¿¿signifying those whose evolutionary trajectories have been profoundly shaped by altered selective regimes in human-dominated landscapes.    

Theme: Recovery and rebuilding of marine and coastal species
Foci: Describe the relationships between human activities and species recovery, rebuilding and sustainability.
Develop methods to use physiological, biological and behavioral information to predict population-level processes.