Plant biodiversity is often partitioned into taxonomic diversity (species composition and abundance), phylogenetic diversity (breadth of evolutionary lineages) and functional diversity (resource-use strategies or physical traits). Evaluating the effects and interplay of these dimensions can provide insights into how assembly processes drive compositional changes in plant communities. However, teasing apart the effects of different biodiversity dimensions is challenging in observational studies or retrospective analyses. To evaluate how plant phylogenetic and trait history shape community establishment and turnover in restoration of a species-rich North American tallgrass prairie, we conducted an experiment with 127 species planted in assemblages representing three levels of phylogenetic diversity (PD) and two of functional trait diversity (FD), holding starting species richness (SR) fixed. We tested whether PD and FD of planted assemblages predicted species diversity, compositional turnover and selection on functional traits. Rank order of initial functional and phylogenetic diversity levels was maintained throughout the experiment, but neither diversity measure correlated positively with species richness by the end of the experiment. Phylogenetic and taxonomic beta diversity increased among all treatments. This increase in compositional beta diversity was associated with directional selection on phylogenetically dispersed functional traits. A set of functional traits associated with competitiveness in tallgrass prairies predicted species' cover for all survey years: stem dry matter content, leaf dry matter content, vegetative height and rhizomatous growth. Although all plots collectively converged on a similar suite of functional traits, functional beta diversity increased among high-FD plots. Synthesis. Neither higher functional nor phylogenetic diversity maintained higher species richness (SR) over time in our study. Although SR was not maintained, higher levels of PD and FD were. Both types of diversity shaped the rate at which plots changed in composition over time, with high diversity treatment plots increasing in beta diversity. Selection for traits convergent across the tree of life drove phylogenetic and compositional divergence among plots. While optimization of site-specific functional traits may be most important for maintaining higher SR, our work implies that planting higher initial PD and FD may make grassland restorations more adaptable to site conditions that may be difficult to predict.
Bibliographical noteFunding Information:
This work was supported by National Science Foundation Awards DEB 1354551 and DEB 1354426. We thank many dedicated volunteers for help with fieldwork (especially Kath Thomas, Ruth Czuprynski, Padma Tota, Janet Knight and John Field), MOR Herbarium staff for assistance in vegetation sampling, seasonal interns who have helped implement this experiment, and The Morton Arboretum Center for Tree Science and departments of Facilities and Living Collections for extensive and ongoing support of this experiment. Anonymous reviewers greatly improved previous versions of the manuscript.
© 2021 British Ecological Society
- community assembly
- compositional divergence
- ecological restoration
- functional diversity
- phylogenetic diversity