Phylogenetic diversity (PD) is a promising tool for restoration. High PD in plant communities has been shown to increase ecosystem functioning and productivity. PD may also influence invasion, but this has been less studied. If high PD promotes invasion resistance, it could be used to guide species selection for restoration to minimize invasions and the associated management costs. PD may influence invasion through two mechanisms: the sampling effect—high PD increases the likelihood of inclusion of competitive natives and the complementarity effect—high PD results in a more ecologically divergent assemblage, decreasing niche space for invaders. A broader range of ecological strategies represented in a high PD system may also increase community stability and maintenance of diversity—a frequent struggle in restoration.
We tested PD of native communities as a predictor of invasive species cover, change in invasive species cover over time, and community stability over time. We used the Critical Trends Assessment Program dataset of standardized vegetation surveys conducted between 1997-2016, encompassing 183 forests, 210 grasslands, and 203 wetlands throughout Illinois. Sites ranged from high-diversity remnant habitat to restored habitat and low-diversity degraded fields, and were surveyed one to four times with five years between surveys.
Results/Conclusions
In this dataset, PD of native communities significantly predicted the relative cover of invasive species during the first survey, with higher PD associated with lower invasive species cover. Additionally, PD of native communities was a significant predictor of change in the invasive species cover after 5 years. However, the was no relationship between PD of the native community and change in invasive species cover after 10 years or after 15 years. Preliminary results indicate that phylogenetic diversity of the native community does not predict community stability or maintenance of biodiversity over time. Overall, these results fail to support the hypothesis that phylogenetic diversity predicts long-term ecosystem stability, they do indicate that the evolutionary history of a native community plays a role in invasion resistance. Further research is needed to address to what degree this effect is being driven by sampling and complementarity effects. Our findings demonstrate that increasing phylogenetic diversity of the native community is a reasonable consideration for decreasing invasion in restorations.