Assistant Professor Cal Poly Humboldt Arcata, California, United States
Abstract: One of the most pervasive patterns in ecology is the decline of biodiversity with latitude and altitude, reflecting changes in temperature, productivity, evolutionary rates, spatial constraints, and species interactions. However, latitudinal gradients in functional diversity are less studied, and results are variable, suggesting different processes may by driving taxonomic and functional diversity. Importantly, the relationship between taxonomic and functional diversity of a regional colonist pool can influence local biodiversity-ecosystem function (BEF) dynamics. Colonist pools that are taxonomically and functionally diverse are predicted to result in strongly positive local BEF relationships. In contrast, colonist pools that are taxonomically diverse but functionally uniform should lead to weak BEF relationships. Here, I aim to establish regional variation on colonist pool taxonomic and functional diversity by profiling microbial communities associated with pitcher plants across latitudinal and biogeographical regions. Carnivorous pitcher plants rely on their microbial communities to degrade the prey they capture within their leaves. Since these plants persist in soils poor in nutrients across their biogeographical ranges, it follows that their microbial communities provide sufficient functional advantage, regardless of the regional diversity or composition. I used a combination of shotgun metagenomics and 16S rRNA gene amplicon sequencing to compare regional taxonomic and functional diversity from microbial communities obtained from S. purpurea and D. californica across 5o latitudinal range within the plants natural distribution. Results suggest that functional redundancy of metabolic traits associated with degradation increases with latitude. Environmental and plant specific factors that vary across plant populations also play a role in driving metabolic networks and their relationship to bacterial diversity. Additionally, S. purpurea exhibited higher redundancy than D. californica, perhaps reflecting its wider range and adaptability, and despite D. californica’s wider diet. Then, I compare these results to microcosm experiments drawn from fluid collected across all sites to reveal that functional redundancy has consequences for local BEF dynamics. By describing some of the potential metabolic networks that underlie invertebrate degradation within the pitcher plant leaf, I propose a generalized framework of regional influences on assembly and BEF relationships. With this first attempt at linking regional functional redundancy to local BEF patterns, we anticipate improving our ability to forecast functional consequences of biodiversity change.
