Abstract

Zooplankton show a unique pattern of evolution with successive waves of invasion into the water column from the benthos. It has been found that 18 of 21 planktonic groups whose ancestry can be traced originated in the benthos. New recruits have survived and radiated if preadapted to remain in the plankton, but no major clades have evolved there. The innovative steps into the planktic realm do not coincide with major global events such as mass extinctions. This unusual pattern of evolution, a one-way track into a particular environment, demonstrates the profound effect of the ecosystem on large-scale patterns and processes of evolution. -from Authors