13 - Small islands ecology

Abstract

Equilibrium theory of biogeography is an important conceptual advance in understanding the patterns of assembly and dynamics of communities on geographical or ecological islands. The theory states that an island, initially devoid of life, is colonized by living things. The rate of immigration of additional species gradually declines as fewer and fewer species on the mainland source area remain as potential new colonists. By looking into the relationship between species and area, information may be obtained by the fact that increase in number of species with area is more rapid in the case of isolated islands or archipelagos than in expanding sample areas on a single land mass. The life history of a colonizing species and its chance for success is certainly important for any colonization process. However, there is a limit to the number of species persisting on a given island. An island is closed to a particular species either when competitor's already in residence excludes the species, or when its population size is held so low that extinction occurs in niche. This chapter focuses on the study of small islands to understand the process of evolution of various water species.