ABSTRACT
Ecological succession is a progression of discrete stages in an ecosystem following a disturbance or colonization. In autogenic succession, each stage improves the environment for the subsequent stage, sometimes even making the environment worse for itself. The subsequent stage also outcompetes the previous stage. Communities increase in complexity, biomass, and diversity with each new stage. The exception to this is that the subclimax stage is more diverse than the stage that follows it, called the climax stage. Disturbances such as fire and herbivores ensure the climax community does not persist indefinitely. Disturbances maximize diversity by ensuring that two or more successional stages occur simultaneously. Herbivores tend to maintain the subclimax community, the most diverse stage. In allogenic succession, animals increase plant diversity. Succession is very common. It is found throughout bacterial communities. Succession occurs on decomposing carcasses. Succession on whale carcasses involves highly diverse stages. As a general rule in succession, organisms increase diversity. Evolutionary succession occurs on long timescales, involving discrete stages with increasing diversity. Examples of evolutionary succession are cyanobacteria aiding phytoplankton, and the recovery from the Cretaceous-Paleogene extinction that killed off the dinosaurs.
