Species diversity in a metacommunity with patches connected by periodic coalescence: a neutral model

Abstract: The recent realization that entire communities fuse and separate (community coalescence) has led to a reappraisal of the forces determining species diversity and dynamics, especially in microbial communities where coalescence is likely widespread. To understand if connectedness by coalescence results in different outcomes from connectedness by individual dispersal, we investigated chance processes leading to loss of species diversity using a model of a neutral two-species metacommunity. Two scenarios were investigated: pairwise coalescence where the communities coalesce in pairs, intermix and then separate; and diffuse coalescence where several communities mix as a pool and are re-distributed to their original patches. When standardized for the same net movement, both types of coalescence led to a longer time to single species dominance than dispersal. Coalescence therefore may be an important process contributing to the surprisingly high microbial species diversity in nature.