Community Diversity: Relative Roles of Local and Regional Processes

TLDR

Local plant and animal diversity results from a balance between regional species addition and local extinction processes, yet studies show that even under similar environmental conditions, local diversity varies and is strongly influenced by regional and historical factors. Ecologists must broaden community process concepts and integrate systematics, biogeography, and paleontology data into ecological pattern analyses and theory tests. The study finds that local diversity often does not converge under similar physical conditions and depends demonstrably on regional diversity.

Abstract

The species richness (diversity) of local plant and animal assemblages—biological communities—balances regional processes of species formation and geographic dispersal, which add species to communities, against local processes of predation, competitive exclusion, adaptation, and stochastic variation, which may promote local extinction. During the past three decades, ecologists have sought to explain differences in local diversity by the influence of the physical environment on local interactions among species, interactions that are generally believed to limit the number of coexisting species. But diversity of the biological community often fails to converge under similar physical conditions, and local diversity bears a demonstrable dependence upon regional diversity. These observations suggest that regional and historical processes, as well as unique events and circumstances, profoundly influence local community structure. Ecologists must broaden their concepts of community processes and incorporate data from systematics, biogeography, and paleontology into analyses of ecological patterns and tests of community theory.