Measuring Functional Diversity Change in Ecological Communities
Kari Norman, University of California, Berkeley
Understanding how ecosystems are changing in response to anthropogenic pressure is essential for appropriately managing and conserving ecological systems into the future. Loss of species diversity is widely cited as the greatest threat to the stability, resilience and functioning of ecosystems. Underpinning this assertion is the assumption that species diversity is an appropriate surrogate for the aspects of species identity and interactions that confer those properties, broadly referred to as functional diversity. However, empirical studies document a wide array of relationships between functional and species diversity and responses of both aspects of diversity to different environmental perturbations are poorly documented. Establishing the relationship between functional and species diversity is further impeded by methodological concerns about the ability of functional diversity metrics to capture change independent of species richness (number of species).
We simulated community assembly and disassembly, two mechanisms by which functional and species diversity change, based on empirical data for multiple communities. Random, best-case and worst-case scenarios of change in diversity were tested by adding and removing species with specific traits. For each community, multiple functional and species diversity metrics were calculated for each scenario to establish the sensitivity of certain metrics to changes in species diversity and identify situations in which this sensitivity is of greatest concern. We lay out recommendations for using certain metrics to detect certain kinds of community change.
Abstract Author(s): Kari E. Norman, Alison G. Boyer