Numerous aquatic insect species inhabiting rivers feed on leaves shed from trees in the surrounding forest. Experiments using alder trees showed that these stream organisms can adapt to feed optimally on individual alder trees growing along their specific river banks; i.e., they feed on locally derived alder leaves faster than on leaves from alder trees growing alongside different rivers. Further studies suggest that aquatic organisms adapt to individual alder trees based on differences in the chemical composition of the leaves. Terrestrial insects feeding on leaves often induces plants to produce chemical deterrents to defend against further feeding, which suggests the hypothesis that variation in the chemical defense system among individual trees influences feeding rate by aquatic organisms. This project will test that hypothesis through chemical analyses to determine the leaf traits causing local adaptation, and by experimentally unraveling the roles of aquatic microbes and insects in driving this adaptation. This research will increase our understanding of the role of biodiversity at the individual level in shaping ecosystem function, illustrate how the ecological interactions in one ecosystem can indirectly shape the structure of other ecosystems through fluxes across boundaries, and illuminate the mechanisms of resilience in river ecosystems.
This research informs two economic pillars of the Olympic Peninsula of Washington, forestry and fisheries, by advancing our understanding of how variation among trees may affect rivers that sustain the region's fisheries. Results from this project will be disseminated to local forest and fisheries managers, including the Elwha and Makah Native American tribes, as well as to the general public. Understanding the ecological effects of individual variation is essential to efforts to predict how genetic diversity, which is rapidly declining due to habitat loss and fragmentation, can alter the functioning of ecosystems. This project will provide research experiences for undergraduates and supports the dissertation research of a doctoral student.
