Biology · Ecology

Given below are four niche-oriented models proposed to explain species-abundance distributions in ecological communities: A. The dominance-preemption model involves successive species preempting a dominant portion (50% or more) of the remaining niche-space. B. In the random fraction model, successive species invade and take over an arbitrary portion of the niche space of any species previously present. Here, irrespective of their dominance status, all species are subjected to niche division with equal pr obability. C. The MacArthur fraction model assumes that larger niches are more likely to be invaded by new species. D. The dominance-decay model postulates that the largest niche in an existing assemblage is always subject to a subsequent (random) division. Assuming a process of community assembly that involves successive species invading and establishing in the community, what would be the correct order of evenness (from lowest to highest) in community structure produced by these mechanisms?