Abstract

Landscape permeability is often explored spatially, but may also vary temporally. Landscape permeability, including partial barriers, influences migratory animals who move across the landscape. Partial barriers are common in rivers where barrier passage varies with streamflow. We explore the influence of partial barriers on the spatial and temporal distribution of migration‐linked genotypes of Oncorhynchus mykiss, a salmonid fish with co‐occurring resident and migratory forms, in tributaries to the South Fork Eel River, California, USA, Elder and Fox Creek. We genotyped >4,000 individuals using RAD‐capture and classified individuals as resident, heterozygous, or migratory‐genotypes using life history‐associated loci. Across four years of study (2014‐2017), the permeability of partial barriers varied across dry and wet years. In Elder Creek the largest waterfall was passable for up‐river migrating adults 4‐39 days/year. In this stream, the overall spatial pattern, with fewer migratory genotypes above the waterfall, remained true across dry and wet years (67‐76% of migratory alleles were downstream of the waterfall). We also observed a strong relationship between distance upstream and proportion of migratory alleles. In Fox Creek, the primary barrier is at the mouth, and we found that the migratory allele frequency varied with the annual timing high flow events. In years when rain events occurred during the peak breeding season, migratory allele frequency was high (60‐68%), and otherwise it was low (30% in two years). We highlight that partial barriers and landscape permeability can be temporally dynamic, and this effect can be observed through changing genotype frequencies in migratory animals.

Citation

Kelson, S.J., Miller, M.R., Thompson, T.Q., O'Rourke, S.M. & Carlson, S.M. (2020): Temporal dynamics of migration‐linked genetic variation are driven by streamflows and riverscape permeability. Molecular Ecology 29 (5): 870-885. DOI: 10.1111/mec.15367

This Paper/Book acknowledges NSF CZO grant support.