Integrating genetic and demographic effects of dispersal on population response to a variable environment

Dr. Allison Dedrick1, Prof Marissa Baskett2

1Rutgers University, Rutgers, United States, 2University Of California, Davis, Davis, United States

Dispersal can have counteracting effects on population response to variable and changing environments.  On one hand, dispersal mobilizes individuals and diversity to increase local response to environmental change.  On the other hand, dispersal can synchronize populations and homogenize genetic diversity throughout a range, decreasing overall population stability and adaptive capacity.  Anthropogenic impacts that alter dispersal provide accidental experiments to explore such counteractive effects.  Motivated by an increase in dispersal through hatchery practices in salmon, hypothesized to have led to synchronous population responses to environmental variability and a resulting fishery collapse, we develop a model of coupled demographic and genetic dynamics under varying levels of dispersal.  In the model, a single trait influences both within-population response to local environmental conditions and across-population response to large-scale environmental forcing, as might occur for phenological traits such as salmon migration and plant flowering time.  We find that increased dispersal can lead to a system-level trade-off between increased average abundance and increased variability in abundance.  This trade-off is much stronger when we include the effects of genetic homogenization than when we consider demographic synchronization alone.  Therefore, we identify an under-appreciated role of genetic homogenization in how dispersal affects population synchrony and variability.  For range shifts, while not explicitly modeled, our results suggest that, while some dispersal will inevitably be necessary to mobilize genes and individuals, too much dispersal can undermine population persistence through homogenization and synchrony, especially if climatic variability increases along with the directional climate change.


Marissa Baskett is an associate professor in the Department of Environmental Science and Policy at the University of California, Davis. Her research focuses on modeling ecological and evolutionary responses to global environmental change, including climate change. She was selected as an Ecological Society of America Early Career Fellow in 2013 and UC Davis Chancellor’s Fellow in 2017. She received her BS in biology from Stanford University and her MA and PhD in ecology and evolutionary biology from Princeton University.

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