Landscape-scale functional diversity of plant, butterfly and bird communities along the Swiss elevation gradient
Applicant: Valentin Amrhein, University of Basel
Co-applicants: Peter B. Pearman (University of the Basque Country), Eric Allen (University of Bern)
Start date: 1 November 2014
Duration: 36 months
Location of research: Switzerland
Support: 281,105 Swiss Franks
The diversity of functional traits in communities (i.e., functional diversity) is increasingly considered to be one of the most relevant components of biodiversity in the context of community ecology and conservation ecology. Here, we propose to examine functional diversity of vascular plant, butterfly and bird communities at a national scale, using data from the biodiversity monitoring program in Switzerland. Within this program, yearly landscape scale surveys have been undertaken since 2001, and the studied sites span an elevation gradient of more than 2'500 meters. The data provide unique opportunities to study patterns of functional diversity in different trophic levels and along a large elevation gradient. We will use contemporary approaches such as structural equation models to infer how the trophic links between plant, butterfly and bird communities change across space and times, and estimate a series of metrics for examining the functional structure of species communities in Swiss landscapes.
From a conservation point of view, landscape-scale studies are central because ecosystems are usually managed, and ecosystem services are delivered, at the landscape scale. Since manipulative experiments are hardly feasible at the landscape scale, inferring patterns from observational studies are necessary to understand relevant trait similarity patterns across landscapes. However, one of the greatest challenges when analysing ecological data of this type is the imperfect detection of species. We will thus study how biases resulting from imperfect detection could be accounted for in research on functional diversity. We will employ site-occupancy analyses using Bayesian posterior sampling to develop methods for estimating functional diversity by accounting for imperfect detection. We will use these methods to draw robust inference on patterns of functional diversity in subsequent analyses.
Combining a multitrophic perspective with an approach based on functional diversity has been suggested as the necessary next step to advance research on community ecology. This is further underpinned by the notion that many ecosystem services ultimately rely on interactions between plants and organisms belonging to other trophic levels. We propose analyses on elevational patterns and temporal trends in functional diversity that will be compared among plant, butterfly and bird communities. We will adopt conceptual frameworks from classic food web research and test predictions using measures of functional diversity. For example, we will test whether the links between trophic levels, quantified based on correlations in their functional diversity, change along a productivity gradient as predicted by a number of theoretical models. Furthermore, we will test whether functional redundancy, which could act to insure the maintenance of ecosystem functioning in the face of species loss caused by global change, varies with the environment and how the degree of redundancy varies between trophic levels. For example, it is currently unknown whether, within the same environments, communities from different trophic levels have similar (i.e., correlated) degrees of functional redundancy.
Overall, our proposed studies will provide a comparative synthesis of the patterns of functional diversity of three trophic levels across Swiss landscapes. The expected results will add to the understanding of the driving forces that structure ecological communities. Since we infer patterns of functional trait diversity, which is currently one of the most promising surrogate measures of community assembly and ecosystem services, the expected results will provide the possibility of mapping the delivery of ecosystem services at the national scale, which complies with the strategic goals of the Swiss biodiversity strategy to quantify ecosystem services across entire Switzerland.