Most knowledge about the role of predation in the workings of nature is ecological, focused on how predation influences community structure. However, many predators disturb plants and substrates when foraging. Some types of disturbance can increase genetic diversity, which can in turn influence species’ potential for adaptation and resilience. In this seminar, I will discuss how my colleagues and I tested the idea that sea otter (Enhydra lutris) digging – a foraging behaviour used to excavate prey from eelgrass (Zostera marina) meadows – could cause disturbance, potentially influencing eelgrass reproductive strategies and genetic diversity. Sea otters once ranged across the Pacific Rim, but were driven to near-extinction by the mid-1850s. Sea otters are recovering in parts of their range, causing a mosaic of areas with and without otters, which we used to design a natural experiment comparing meadows from areas where otters were present for decades, a few years, or were absent. We found that eelgrass allelic richness and genotypic diversity were, respectively, 30 and 6% higher in meadows where otters were established for 20-30 years, than where they had recently arrived (<10 years), or were absent. We infer that otter digging disturbs eelgrass, increasing flowering compared to vegetative reproduction, and provides conditions for seed set and growth. We tested if meadow size, depth, and temperature affected eelgrass genetic diversity, but found the association between otters and eelgrass was strongest. When sea otter populations were severely reduced, their effects on eelgrass genetic diversity were lost. Our findings highlight an underappreciated evolutionary process by which sea otter recovery can contribute to ecological resilience, and illustrate a novel consequence of trophic downgrading that may apply broadly across systems where large fauna have been functionally eliminated. I will discuss these potential implications, and approaches we may use to evaluate such ideas.

The Natural Resources & Environmental Studies Institute (NRESi) at UNBC hosts a weekly lecture series at the Prince George campus. Anyone from the university or wider community with interest in the topic area is welcome to attend. Go to http://www.unbc.ca/nres-institute/colloquium-webcasts to view the presentation remotely.

Past NRESi colloquium presentations and special lectures can be viewed on our video archive, available here.

Please Note: NRESi colloquium presentations this semester will be available to attend both in-person as well as online. However, it is recommended that those wishing to attend in-person wear a mask as per University policy. Thank you for your understanding.