@article {2358,
	title = {Consequences of individual species loss in biodiversity experiments: an essentiality indez},
	journal = {Acta Oecologica},
	volume = {32},
	year = {2007},
	pages = {236-242},
	abstract = {The importance of species richness for ecosystem productivity has received much atten- tion in recent years, but the consequences of non-random species extinction remain poorly understood. We propose an index, {\textquoteleft}essentiality{\textquoteright}, to assess the consequence of extinction of particular species for community biomass production. The essentiality of a species in a given community is the extent to which the functional role of that species is irreplaceable by the remaining species, calculated as the relative difference in yields between communi- ties with and without the focal species. Species with zero essentiality play a completely re- placeable functional role in their communities. Positive essentialities suggest irreplaceable contributions by species to their communities; species with essentiality values even higher than their dominance in the community may exhibit facilitative effects on the other spe- cies. Negative essentialities indicate interference of the focal species with other members of the same community. We applied this index to data from a microcosm experiment, in which five algal species were grown in monocultures and in all possible species combina- tions. Essentiality varied greatly across species. Two species had overall zero essentiality values throughout the experiment, two species had positive essentiality values which were lower than the species{\textquoteright} dominance, and the remaining species had negative essenti- ality. Furthermore, two out of the five species had essentiality values dependent on species richness of communities from which they were lost; essentiality decreased with an in- crease in species richness. The essentiality index provides a straightforward measurement of functional consequences of individual species loss, which complements the existing an- alytical methods by focusing on the detection of facilitation and interference. },
	keywords = {Algal microcosm, complementarity, productivity, selection effect, Species diversity},
	author = {Zhang, Quan-Guo and Zhang, Da-Yong}
}
