Coexistence of complete competitors with fitness inequality

Abstract

There was a long standing contradiction between formulations of the competitive exclusion principle and natural species richness, which is known as the biodiversity paradox. Here we investigate a role of fitness differences in coexistence of two completely competing species using individual-based cellular automata. According to the classical formulations of the competitive exclusion principle such coexistence is impossible. Earlier we found that coexistence of complete competitors is possible with a 100% difference in fitness, but only under certain initial conditions. Here we verify a hypothesis that completely competing species may coexist with less than 100% difference in fitness regardless of different initial location of competing individuals in the ecosystem. We have found a new fact that two aggressively propagating complete competitors can stably coexist in one limited, stable and homogeneous habitat, when one species has some advantage in fitness over the other and all other characteristics of the species are equal, in particular any trade-offs and cooperations are absent. This fact is established theoretically on the rigorous model. The found competitive coexistence occurred regardless of the initial location of individuals in the ecosystem. When colonization of free habitat started from a single individual of each species, then the complete competitors coexisted up to 31% of their difference in fitness. And when on initial stage half of the territory was probabilistically occupied, the complete competitors coexisted up to 22% of their difference in fitness. These results additionally support our reformulation of the competitive exclusion principle, which we consider as resolving of the biodiversity paradox.