Fig. la-c. Hypothetical relationships between species richness
and ecosystem processes (e.g.
primary production, nutrient cycling) (from Naeem et al. 1995)
within one locality. a The redundant species hypothesis. b The
rivet hypothesis. c The idiosyncratic hypothesis. See text for
details
8. Biodiversity and Ecosystem Processes
121
a
b
SPECIES RICHNESS
and Ehrlich 1981), so that ecosystem processes are progressively more impaired as species are lost from the system (Fig. 1b).
(iii) The idiosyncratic hypothesis again postulates that species are important in
ecosystem processes, but particular species identities matter more than species
richness per se (Lawton 1994; Chapin et al. 1997; Tilman 1997). In consequence, ecosystem processes change erratically and unpredictably as species
are lost from the system (Fig. 1c).