Chapter 11 - Evolution of Organisms and Biodiversity of Freshwaters

Abstract

This chapter focuses on the evolution of organisms and biodiversity of freshwaters. The simplest measure of diversity is species richness, the total number of species found in an area. The ultimate source of biological diversity is evolution. Two main factors influence the evolution of new species: time available for evolution and reproductive isolation. These factors, coupled with the mosaic nature of the environment (spatial and temporal aspects of habitat heterogeneity), have resulted in millions of species. One of the most striking demonstrations of the importance of evolution to biological diversity is the high number of species found in geologically ancient habitats that have had ample time for new species to arise. Genetic diversity within populations and species is important for long-term survival. Conservation efforts and aquaculture programs are increasingly focused on maintenance of genetic diversity. Population size is a critical factor in the survival of species. Spatial arrangement of subpopulations, metapopulation structure, is also important for evolution and conservation of species.