Evolutionary diversification and the origin of the diversity-environment relationship.

Global patterns in species richness have resisted explanation since they first caught the attention of ecologists in the 1960s. The failure of ecology to fully integrate the diversity issue into its core of accepted wisdom derives from an inappropriate concept of community and the rejection of history and region as formative contexts for ecological systems. Traditionally, ecologists have held that the pervasive relationship between species richness and conditions of the physical environment reflects the influence of environment on the ability of populations to coexist locally. However, many ecologists now recognize that this relationship can also develop historically from the evolutionary diversification of lineages within and between ecological zones. To assess the relative roles of local ecological constraint vs. regional and historical unfolding of diversity-environment relationships, we must abandon localized concepts of the community and adopt historical (particularly phylogenetic) and geographic methods to evaluate the evolution of diversity within large regions and its influence on diversity at local scales. This integrated perspective opens new research directions for ecologists to explore the formation of species, adaptive diversification, and the adjustment of ecological distributions of species on regional scales.