1. Evolution (and loss) of biodiversity among salmon populations
Pacific salmon (Oncorhynchus spp.) are renowned for their extensive phenotypic and life history diversity. This biodiversity among salmon populations is thought to be important for long-term sustainability of population complexes due to shifts in production among the different life history components as a function of the prevailing environmental conditions. I strive to understand the processes generating biodiversity among salmon populations, as well as their consequences. To this end, I conduct research that illuminates the ecological circumstances driving variation in natural selection among salmon populations, including variation in biotic (e.g., predation) and abiotic (e.g., climate) factors. This research is important in showing how environmental heterogeneity contributes to the evolution of biological diversity.
In an effort to understand the rate and direction of evolution in salmon populations, I worked with Todd Seamons to review estimates of two quantitative parameters in salmonine fishes, narrow-sense heritability (h2) and genetic correlation (rG). These data provide a useful starting point for predicting how salmon populations will respond to human-induced selection (e.g., population harvest and habitat degradation). I am also interested in understanding the consequences of biodiversity loss on the resilience, stability, and sustainability of salmon populations. I recently collaborated on a project which demonstrated that a selective loss of upland tributaries due to dam construction has resulted in a selective loss of salmon populations and life history components. I am currently developing several projects related to the evolution and loss of biodiversity among California’s salmon populations as I believe this work will improve our ability to manage and recover California’s ESA-listed stocks.
2. Eco-evolutionary dynamics
My expanding research interests include a focus on eco-evolutionary dynamics, that is, understanding how contemporary selection and evolution influence populations, communities, and ecosystems. Much of my work on Pacific salmon falls under the purview of eco-evolutionary dynamics but I am expanding into other study systems as well. With Jon Moore, for instance, I am exploring the evo-evolutionary dynamics of two dominant invasive species in California streams, New Zealand mudsnails (Potamopyrgus antipodarum) and signal crayfish (Pacifastacus leniusculus).
3. Harvest selection and evolution
I am very interested in understanding the role of “human predators” as agents of trait change in wild populations. Humans differ from other predators both in terms of the magnitude (number of individuals killed) and selectivity (traits of individuals killed) of predation. With Nils Chr. Stenseth and others at the Centre for Ecological and Evolutionary Synthesis in Oslo, I quantified the form of natural and fishery selection acting on northern pike (Esox lucius) in Lake Windermere (U.K.) and found that the two selective forces often acted in opposition. Moreover, natural and fishery selection combined to reduce fitness overall and strengthen stabilizing selection relative to natural selection acting alone. These results set the stage for further work in which we investigated the relative role of harvest versus natural selection in driving phenotypic trait change in Windermere pike. More recently, I have been working with a group led by Chris Darimont to evaluate phenotypic changes in human-harvested populations. This work revealed that phenotypic changes in exploited prey outpace those in more natural contexts by 300%, on average. Ongoing research in this area is focused on examining among-system variation in the magnitude of trait changes as well as disentangling phenotypic versus genetic changes in harvested fish populations, a topic of considerable interest to both fisheries scientists and evolutionary biologists.
4. Evolutionary enlightened management
Recent research has demonstrated that adaptive evolution occurs on contemporary time scales (i.e., decades) and, moreover, that adaptive evolution is often associated with the same anthropogenic factors driving the current extinction crisis (e.g., overharvest, exotic species, habitat degradation). A long-term goal of mine is to apply evolutionary principles to guide management, conservation, and restoration efforts. Explicit consideration of the evolutionary challenges facing species and populations of concern should result in more effective management and conservation efforts. If this topic interests you, check out Evolutionary Applications, a new journal devoted to these issues.
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