2018 ESA Annual Meeting (August 5 -- 10)

COS 58-7 - The roles of host tree genetics and environment in structuring arthropod communities: A macrosystems approach to community ecology

Wednesday, August 8, 2018: 10:10 AM
356, New Orleans Ernest N. Morial Convention Center
Helen M. Bothwell1, Arthur R. Keith2, Julia B. Hull1, Samuel A. Cushman3, Tom Whitham4 and Gerard J. Allan1, (1)Biological Sciences, Northern Arizona University, Flagstaff, AZ, (2)Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, (3)Rocky Mountain Research Station, US Forest Service, Flagstaff, AZ, (4)Biological Sciences, Northern Arizona University
Background/Question/Methods

Rapid global climate change is shifting species distributions and altering community assemblages across the landscape. Faced with these challenges, a major question is to what extent will communities shift together or exhibit individual migration rates. Research in the fields of community and ecosystem genetics has found that genetic variation in foundation species plays a major role in structuring associated communities and ecosystem processes, for example, explaining 39-78% of variation in community biodiversity and 32% of variation in arthropod community stability from year to year. Yet, few studies to date have investigated the interaction between host tree genetics and environmental control on arthropod community assembly at the landscape scale. Here we expand from common garden studies and utilize a macrosystems approach to predict community consequences of climate change across southwestern riparian areas. Using genome-wide SNP data, we assessed genetic diversity and connectivity for 322 individual Fremont cottonwood trees at 58 sampling sites spanning Arizona, Utah, Nevada, and California. From the same trees, we measured community composition and diversity for associated fungal endophytes and leaf modifying arthropods. Using a landscape genetic model, we then quantified the relative contributions of host tree genetics and environmental variation in structuring arthropod communities across the landscape.

Results/Conclusions

Four major findings emerged. 1) Fremont cottonwood is genetically differentiated into three major ecoregions, comprising the Sonoran Desert, Utah High Plateau, and California Central Valley, and 2) each ecoregion occupies a significantly different, largely non-overlapping climate niche. 3) Both the leaf modifying arthropod and fungal endophyte communities were significantly differentiation across cottonwood ecotypes, with genetic distance among host trees explaining 13-19% of distance among associated communities, respectively. 4) After accounting for the effect of host genotype, we still observed a significant, independent effect of climate, with precipitation seasonality and growing degree days above 5°C showing the strongest contributions to community differentiation. Our results suggest that foundation species genetics is a critical component structuring associated communities across the landscape. Furthermore, our findings suggest that both cottonwood and its associated community members are locally adapted within ecoregions, therefore care should be taken to avoid crossing restoration planting stock across major ecoregions.