The importance of niches for the maintenance of species diversity

Jonathan M. Levine1 & Janneke HilleRisLambers2

Ecological communities characteristically contain a wide diversity
of species with important functional, economic and aesthetic value.
Ecologists have long questioned how this diversity is maintained1–3.
Classic theory shows that stable coexistence requires competitors to
differ in their niches4–6; this has motivated numerous investigations
of ecological differences presumed to maintain diversity3,6–8. That
niche differences are key to coexistence, however, has recently been
challenged by the neutral theory of biodiversity, which explains
coexistence with the equivalence of competitors9. The ensuing
controversy has motivated calls for a better understanding of the
collective importance of niche differences for the diversity observed
in ecological communities10,11. Herewe integrate theory and experimentation
to show that niche differences collectively stabilize the
dynamics of experimental communities of serpentine annual
plants. We used field-parameterized population models to develop
a null expectation for community dynamics without the stabilizing
effects of niche differences. The population growth rates predicted
by this null model varied by several orders of magnitude between
species, which is sufficient for rapid competitive exclusion.
Moreover, after two generations of community change in the field,
Shannon diversity was over 50 per cent greater in communities
stabilized by niche differences relative to those exhibiting dynamics
predicted by the nullmodel. Finally, in an experimentmanipulating
species’ relative abundances, population growth rates increased
when species became rare—the demographic signature of niche
differences. Our work thus provides strong evidence that species
differences have a critical role in stabilizing species diversity.

全文下载：userfiles//Levine_Nature_09.pdf