Eligibility: This project is only available to students on the online MSc Statistics and Data Science programme. If you are interested, please contact Dr. Rishabh Vishwakarma at rishabh.vishwakarma@tcd.ie
Biodiversity and ecosystem function (BEF) studies investigate how diversity, including the number of species and their relative proportions affect the outputs (functions) of an ecosystem. Commonly, BEF experiments establish communities with different species and varying sown proportions at a timepoint t and measure a response of interest such as dry matter yield or forage quality at time point t + 1. The aim of the experiment is to quantify the effect of manipulation in species diversity on the response of interest.
Diversity-Interactions models (DI; Kirwan et al., 2007) are one approach for modelling the BEF relationship and use the sown proportions of species as predictors to quantify the effects of species identities (i.e., inherent contribution) and their interactions on the response. However, species communities may not always establish at the intended sown proportions and may end up having substantially different realised proportions. For example, a community sown with equal proportion of species A and B, i.e., 0.5 each, may establish with proportions of 0.9 and 0.1, respectively. In such cases, modelling the BEF relationship using the sown proportions may lead to misleading conclusions about the effect of species diversity on the response.
This project will use simulation studies to compare models based on sown versus realised species proportions as predictors and assess how deviations from sown proportions affect model coefficients. The specific questions of interest would be
1) What is the threshold for deviations from sown proportions beyond which model estimates change drastically?
2) How do deviations in sown proportions towards specific species affect the magnitude and direction of particular species interactions?
The results from this project will inform best modelling practices for BEF experiments where species establishment is uncertain. If you are interested, please contact Dr. Rishabh Vishwakarma at rishabh.vishwakarma@tcd.ie.
Recommended reading (in order):
Kirwan, L., Connolly, J., Finn, J. A., Brophy, C., Luscher, A., Nyfeler, D., & Sebastià, M. T. (2009). Diversity-interaction modeling: Estimating contributions of species identities and interactions to ecosystem function. Ecology, 90, 2032–2038.
Connolly, J., Bell, T., Bolger, T., Brophy, C., Carnus, T., Finn, J. A., Kirwan, L., Isbell, F., Levine, J., Lüscher, A., Picasso, V., Roscher, C., Sebastia, M. T., Suter, M., & Weigelt, A. (2013). An improved model to predict the effects of changing biodiversity levels on ecosystem function. Journal of Ecology, 101, 344–355.
Moral, R.A., Vishwakarma, R., Connolly, J., Byrne, L., Hurley, C., Finn, J.A. and Brophy, C., 2023. Going beyond richness: Modelling the BEF relationship using species identity, evenness, richness and species interactions via the DImodels R package. Methods in Ecology and Evolution, 14(9), pp.2250-2258.