Plant functional traits often show local adaptation to climate and other environmental variables. This phenotypic variability within foundation species, especially in those with large ranges, can structure dependent communities. The riparian foundation tree species Fremont cottonwood, Populus fremontii, has a large geographical range and is separated into three distinct ecoregions determined by geography, climatic niche, and genetic structure. We used this system to examine the following questions: 1) Do canopy traits, twig endophyte communities, and/or leaf-modifying arthropod communities differ among ecoregions? 2) Are plant traits correlated with dependent communities? 3) Is there a correlation between endophyte community structure and leaf-modifying arthropod community structure? We collected Fremont cottonwood twigs from 48 source populations representing the three ecoregions. Leaf and twig traits were quantified. Leaf-modifying arthropod communities were determined in the field and endophyte communities were determined using Illumina amplicon sequencing of the ITS1 gene region.
Results/Conclusions
To date, our results show cottonwoods in different ecoregions have distinct canopy traits, leaf-modifying arthropod communities, and twig endophyte communities. Specifically, the Sonoran Desert ecoregion has longer, thinner branches with more leaves with less surface area than the other two ecoregions. The Utah High Plateau ecoregion had leaves with ~20 to 25% greater surface area than the California Central Valley and Sonoran Desert ecoregions, respectfully. While the endophyte and leaf-modifying arthropod communities were different in all ecoregions, the California Central Valley and Utah High Plateau were more similar to each other than to the Sonoran Desert ecoregion. Further analyses will include Mantel and partial Mantel tests to determine community correlation between leaf-modifying arthropod communities and twig endophyte communities and their relationship to canopy traits. We predict that canopy traits will be linked to the structure of the dependent communities. This on-going study shows that climatic conditions shape intraspecific variation in plant functional traits in a foundation species, which likely has cascading effects on dependent communities.