Hal Caswell (1949–), Stephen P. Hubbell (1942–)
1920 Frederic Clements describes how plant species are associated with each other in communities.
1926 Henry Gleason proposes that ecological communities are organized more randomly.
1967 Richard Root introduces the concept of the ecological guild—a group of species exploiting resources in similar ways.
2018 A review headed by Dutch ecologist Marten Scheffer suggests that, although species that use the same resources may be competitively equivalent, they may also differ according to their response to stress-inducing factors, such as drought or disease.