In search for universal patterns in the organization of communities: The concept of neutrality has paved the way to a new approach
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- Gilyarov, A.M. Biol Bull Rev (2011) 1: 13. doi:10.1134/S2079086411010038
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The concept of neutrality, which presents a new view of the problem associated with the coexistence of species competing for shared resources, has recently stimulated renewed interest in the structure of communities. Unlike the traditional concept, which states that species must occupy different ecological niches, the concept of neutrality assumes that species can successfully coexist due to their ecological similarity and close rates of their specific (per individual) reproduction, extinction, and colonization of free space. An analysis of the vast literature on the new concept allowed us to formulate the following questions: (1) What do we actually mean when we speak about the coexistence of species? (2) How can we explain the presence of numerous rare species in a community against a background of a small number of abundant species? (3) Do rare species have any advantages compared to abundant species? (4) Can the mechanisms implied by the concept of neutrality and the traditional niche approach work simultaneously in the same community? When trying to answer these questions, we should do the following: (1) reject the demand for the infinitely long coexistence of species, which is considered obligatory in all models; (2) accept that the ratio of relative abundances of species observed in communities (a large number of rare species against a background of a few abundant species) results not only from ecological processes (dispersal, competition, etc.), but also from evolutionary mechanisms (formation of the initial pool of species); (3) admit that rare species have certain advantages for survival compared to abundant species; (4) accept that species in any multispecies community can coexist either by occupying different ecological niches or by approaching ecological similarity. Despite the advances made in understanding the general principles in community organization, the question posed by Hutchinson 50 years ago of why there are so many kinds of animals has yet to be answered.