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 fish) Catch 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
Salmon hatcheries
Ocean River 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 Proportion released Bay to
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: Stray 20
0 dispersal between dispersal 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 survivorship H 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 H adults survivorship • Harvest mortality Trucking distance Trucking increases genetic similarity
Both
Creek w/o hatchery Mean genotype Mean Creek w/hatchery variance Genetic
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 outweighs homogenization Genetic
Variance of total return Mean spawner population size (x10 population Mean spawner evolution With synchrony effectssynchrony 4 distancetrucked: of Proportion ) 0 0.5 1 Dedrick American Naturalist &Baskett 2018, 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