Resilience is a general concept that aims to help understand how ecosystems respond to disturbances such as extinctions and invasions. Here, we propose a measure of one aspect of resilience, RX, which is one minus the expected change in functional diversity (X) caused by a species extinction or addition. We show how two components of biodiversity, species richness and functional diversity, and the structure of regional species pools affect this measure. Variation in species richness and in functional diversity have opposite effects on RX. Speciose assemblages generally have higher RX than depauperate ones, whereas functionally diverse assemblages have low RX relative to functionally depauperate ones. The effect of an extinction on RX reflects this tradeoff. In our analyses, extinctions usually cause only a small decrease in both functional diversity and RX. However, extinctions sometimes cause a large reduction in functional diversity and then tend to increase RX. Regional assemblages containing all rather unique species tend to result in speciose assemblages with relatively low RX and in low richness assemblages with relatively high RX. The opposite is true of regional assemblages containing functionally similar species. Information about the processes that structure regional assemblages will therefore increase understanding of ecosystem resilience. Generally, these results suggest that management for biodiversity may not always result in management for resilience.
- Environmental change
- Specie straits