Helmut Hillebrand, Danuta M. Bennett, and Marc W. Cadotte. 2008. Consequences of dominance: A review of evenness effects on local and regional ecosystem processes. Ecology 89:1510–1520.

Appendix A. A glossary of terms related to ecosystem function.

Beta diversity: a measure of among-habitat diversity. Measures can be multiplicative as in similarity indices or additive where beta is the difference between mean local and regional diversities.

Complementarity: the idea that measures of ecosystem function in species-rich plots are greater than estimates from monocultures of the constituent species meaning that co-occurring species utilize different niches. Statistical measures of overyielding are thought to be produced by complementarity.

Diversity: a term that describes several measures of either the richness of species and/or the distribution of abundances. The most common metric, the Shannon Index, combines richness and abundances and allows for a simple calculation of evenness (see ‘Evenness’). The Shannon Index is defined as:

where S is the number of species, n_i the abundance of species i, and N is the total abundance of all species.

Evenness: though generally defined in this paper as communities where species have relatively even abundances, there are more specific definitions. For example evenness,

where is the Shannon index (see ‘Diversity’) and

Functional evenness: describes the distribution of functional traits within a community, as opposed to species alone.

Insurance hypothesis: in species rich communities, ecosystem function is stable despite fluctuating environments due to insurances that species take over functional roles when others fail.

Metacommunity: community patterns and processes are often multi-scale phenomena, and thus require explicit parsing into spatial components. Species interact at small spatial scales but communities are not independent as dispersal links communities together, thus dynamics at one scale may have consequences at others.

Resilience: the ability of a community to recover from disturbance and return to previous level of function. It can also be defined as a “return time” to a stable state following a perturbation.

Resistance: the ability of a community to withhold (resist) a change in face of a disturbance.

Selection effects: measures of ecosystem function are largely a reflection of the dominant species. Lack of overyielding is thought to indicate that function measures in species-rich communities are equal to expected values based on species performances in monoculture.

Source-sink dynamics: populations in optimal locales likely show high reproductive success and are propagule sources for suboptimal locales. These additional propagules enhance population birth rates, and if supplemented births are greater than deaths, the population will persist.