Integrating genetic and demographic effects of dispersal on population response to a variable environment Allison G. Dedrick Dept. of Ecology, Evolution, and Natural Resources, Rutgers University & Marissa L. Baskett (presenting) Dept. of Environmental Science and Policy, University of California Davis Dispersal is a double-edged sword ↑ Local rescue: • Demographic support • Increase local diversity Mobilized individuals & genes → ↑ response to climate change ↑ Cross-population variability: • Demographic synchrony • Genetic homogenization What is the relative role of demographic versus genetic dynamics in driving the effect of dispersal? Lenormand 2002, → drivers of +/- roles in response to climate change Abbott 2011 Humans are altering dispersal Habitat fragmentation ↑ Local rescue: • Demographic support • Increase local diversity Transport ↑ Cross-population variability: • Demographic synchrony • Genetic homogenization Including variability in returns for a natural resource What is the relative role of demographic versus genetic dynamics in driving the effect of dispersal? human impacts^ on Study system: salmon → naturally high genetic differentiation Ocean Waples et al 2004 River Independent & diverse populations stabilize returns Sockeye salmon (Oncorhynchus Aggregate returns nerka) to Bristol Bay were 41-77% more stable than individual stocks (Schindler et al. 2010) Catch (millions (millions Catch fish) of Year Slide courtesy: S. Carlson Increased variability in California Habitat: Chinook (Oncorhynchus - Current tshawytscha) Sacramento Basin: - Former 8/10 + pairwise (barrier/d correlations am) 4 significant San Joaquin Basin: 6/6 + pairwise correlations 4 significant Adult production production (thousands) Adult Year Slide courtesy: S. Carlson Increased variability in California Chinook (Oncorhynchus tshawytscha) Adult production production (thousands) Adult Year Slide courtesy: S. Carlson River Ocean Salmon hatcheries Salmon hatcheries: trucking Hatchery 1950 1960 1970 Nimbus hatchery release sites 1980 1990 2000 Juvenile Redeye Bass Chinook Satterthwaite & Carlson 2015.; Sturrock et al. 2019; Huber & Carlson 2015 Slide courtesy: S. Carlson 6e+07 a) 5e+07 h s i f 4f e+07 o r Salmon hatcheries: trucking 3e+07 e b 2m e+07 u 1N e+07 0e+00 Hatchery 1950 1960 1970 1950 1960 1970 1980 1990 2000 2010 Release year y a 1.0 B o t 0.8 d e s a 0.6 e l e r 0.4 n o i t r 0.2 1980 1990 2000 o p o r 0.0 P (all 5 hatcheries) 5 (all 1950 1960 1970 1980 1990 2000 2010 Year Proportion released to Bay Nimbus hatchery Satterthwaite & Carlson 2015.; Sturrock et al. 2019; Huber & Carlson 2015 Slide courtesy: S. Carlson Trucking increases dispersal between streams 100 y = 0.1617x + 8.5805 2 80 R = 0.8743 60 40 Stray Index: 20 0 dispersal dispersal between streams 0 100 200 300 400 500 600 Distance (km) of release from Coleman Hatchery CDFG/NMFS 2001; Hanak et al. 2011; Lindley et al. 2009 Slide courtesy: S. Carlson Central questions • Can increased dispersal (through trucking) explain the increased variability in California’s salmon? o What is the relative contribution of demographic synchrony versus genetic homogenization to increased variability? Model Reproduction & River A density-dependence Within-river Hatchery A* outmigration River B survivorship and Fry selection Spawners Follow joint demographic- Smolt genetic dynamics Ocean arrival Return migrants time selection Outmigrants density Population Population Return Genotype & straying Ocean Ocean adults survivorship Model Reproduction & River A Within-river H survivorship density-dependence Selection strength Hatchery A* outmigration Trucking distance • Random mating Fitness River B survivorship and • Offspring production Optimal trait Fry Hatchery selection • Density dependence Spawners Phenotype in wild populations transport Trait: migration Hatchery Smolt timing removal Ocean arrival Fry Return migrants time selection Eggs Outmigrants Return & straying Ocean Ocean • Natural mortality H straying adults survivorship • Harvest mortality Trucking distance Trucking increases genetic similarity Both Creek w/o hatchery Mean genotype Creek w/hatchery Genetic variance Proportion of distance trucked Dedrick & Baskett 2018, American Naturalist Population size and variability increase w/trucking Both spawners spawners Creek w/hatchery Mean # Mean Creek w/o hatchery # in Variance Proportion of distance trucked Dedrick & Baskett 2018, American Naturalist Trade-off between population size and variability With Proportion of evolution distance trucked: 1 total returntotal 0.5 Variance of Variance 0 Dedrick & Baskett 2018, 4 Mean spawner population size (x10 ) American Naturalist Genetic homogenization outweighs demographic synchrony effects With Proportion of evolution distance trucked: 1 total returntotal 0.5 Variance of Variance 0 Dedrick & Baskett 2018, 4 Mean spawner population size (x10 ) American Naturalist Conclusions • Trucking can drive increased variability in salmon o Genetic homogenization >> demographic synchrony in driving increased variability • For SOTM: o There can be a such thing as too much dispersal, especially: a) Considering genetic differentiation across locations, & b) If environmental variation increases with climate change Acknowledgements Co-author: Allison Dedrick Funding: Project collaborators: Stephanie Carlson, Mike Springborn, Amanda Faig, Will Satterthwaite, Steve Lindley, Robin Waples.