Coexistence mediated by recruitment fluctuations: a field guide to the storage effect.

For most species, a changeable environment creates a situation in which recruitment varies considerably from one breeding season to the next. If adults survive well, an occasional favorable recruitment can sustain population numbers over long periods: gains made in favourable periods are stored in the adult population. Storage is particularly important when the species is at low densities, because then the potential population growth rate is very high if a favorable period occurs. Storage mechanism can lead to coexistence of 2 species in lottery competition for space, as long as generations overlapped and there was sufficient variation in recruitment. This was true even if one species had an average competitive advantage. The storage model also operates when >2 species are competing, when resources renew independently of population sizes, and when not all the resource is used. Species with relatively long lives and high fecundities are most likely to enjoy the benefits of the storage effect. Environments that theoretically elicit these life history characteristics are relatively benign and permanent for established adults, but are such that births and/or juvenile survivorship vary widely. Trees and many marine organisms are examples of species with the proper life histories, and storage may be important in maintaining the high diversity of these communities.-from Authors