title: Evolutionary consequences of habitat loss for Pacific anadromous salmonids.
abstract: Large portions of anadromous salmonid habitat in the western United States has been lost because of dams and other blockages. This loss has the potential to affect salmonid evolution through natural selection if the loss is biased, affecting certain types of habitat differentially, and if phenotypic traits correlated with those habitat types are heritable. Habitat loss can also affect salmonid evolution indirectly, by reducing genetic variation and changing its distribution within and among populations. In this paper, we compare the characteristics of lost habitats with currently accessible habitats and review the heritability of traits which show correlations with habitat/environmental gradients. We find that although there is some regional variation, inaccessible habitats tend to be higher in elevation, wetter and both warmer in the summer and colder in the winter than habitats currently available to anadromous salmonids. We present several case studies that demonstrate either a change in phenotypic or life history expression or an apparent reduction in genetic variation associated with habitat blockages. These results suggest that loss of habitat will alter evolutionary trajectories in salmonid populations and Evolutionarily Significant Units. Changes in both selective regime and standing genetic diversity might affect the ability of these taxa to respond to subsequent environmental perturbations. Both natural and anthropogenic and should be considered seriously in developing management and conservation strategies.
authors.affiliation: Northwest Fisheries Science Center Seattle, WA.
authors.forename: Michelle M
authors.initials: MM
authors.lastname: McClure
authors.affiliation: University of California Santa Cruz, CA.
authors.forename: Stephanie M
authors.initials: SM
authors.lastname: Carlson
authors.affiliation: Northwest Fisheries Science Center Seattle, WA.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Beechie
authors.affiliation: Northwest Fisheries Science Center Seattle, WA.
authors.forename: George R
authors.initials: GR
authors.lastname: Pess
authors.affiliation: Northwest Fisheries Science Center Seattle, WA.
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Jorgensen
authors.affiliation: Southwest Fisheries Science Center Santa Cruz, CA.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Sogard
authors.affiliation: Wesleyan University Middletown, CT.
authors.forename: Sonia E
authors.initials: SE
authors.lastname: Sultan
authors.affiliation: Northwest Fisheries Science Center Seattle, WA.
authors.forename: Damon M
authors.initials: DM
authors.lastname: Holzer
authors.affiliation: Florida State University Tallahassee, FL.
authors.forename: Joseph
authors.initials: J
authors.lastname: Travis
authors.affiliation: Northwest Fisheries Science Center Seattle, WA.
authors.forename: Beth L
authors.initials: BL
authors.lastname: Sanderson
authors.affiliation: University of California Berkeley, CA.
authors.forename: Mary E
authors.initials: ME
authors.lastname: Power
authors.affiliation: Oregon Department of Fish and Wildlife La Grande, OR.
authors.forename: Richard W
authors.initials: RW
authors.lastname: Carmichael
keywords: Oncorhynchus; dams; differential habitat loss; evolutionary trajectory; genetic variation