Restricted gene flow between resident Oncorhynchus mykiss and an admixed population of anadromous steelhead

Ecology and Evolution
By: , and 

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Abstract

The species Oncorhynchus mykiss is characterized by a complex life history that presents a significant challenge for population monitoring and conservation management. Many factors contribute to genetic variation in O. mykiss populations, including sympatry among migratory phenotypes, habitat heterogeneity, hatchery introgression, and immigration (stray) rates. The relative influences of these and other factors are contingent on characteristics of the local environment. The Rock Creek subbasin in the middle Columbia River has no history of hatchery supplementation and no dams or artificial barriers. Limited intervention and minimal management have led to a dearth of information regarding the genetic distinctiveness of the extant O. mykiss population in Rock Creek and its tributaries. We used 192 SNP markers and collections sampled over a 5‐year period to evaluate the temporal and spatial genetic structures of O. mykissbetween upper and lower watersheds of the Rock Creek subbasin. We investigated potential limits to gene flow within the lower watershed where the stream is fragmented by seasonally dry stretches of streambed, and between upper and lower watershed regions. We found minor genetic differentiation within the lower watershed occupied by anadromous steelhead (FST = 0.004), and evidence that immigrant influences were prevalent and ubiquitous. Populations in the upper watershed above partial natural barriers were highly distinct (FST = 0.093) and minimally impacted by apparent introgression. Genetic structure between watersheds paralleled differences in local demographics (e.g., variation in size), migratory restrictions, and habitat discontinuity. The evidence of restricted gene flow between putative remnant resident populations in the upper watershed and the admixed anadromous population in the lower watershed has implications for local steelhead productivity and regional conservation.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Restricted gene flow between resident Oncorhynchus mykiss and an admixed population of anadromous steelhead
Series title Ecology and Evolution
DOI 10.1002/ece3.3338
Volume 7
Issue 20
Year Published 2017
Language English
Publisher Wiley
Contributing office(s) Western Fisheries Research Center
Description 14 p.
First page 8349
Last page 8362
Country United States
State Washington
Other Geospatial Rock Creek Subbasin