Incomplete mixing promotes species coexistence in a lottery model with permanent spatial heterogeneity

For many marine organisms, the population dynamics in multiple habitats are affected by migration of planktonic larvae. We herein examine the effect of incomplete larval mixing on the condition for species coexistence. The system consists of two heterogeneous habitats, each composed of a number of sites occupied by adults of two species. Larvae produced in a habitat form a pool and migrate to the pool of the other habitat. When an adult dies, the vacant site becomes occupied by an individual randomly chosen from the larval pool. We study (1) the invasibility of a inferior species which has no advantage in either habitats, (2) the dynamics when larval migration and competition among adults are symmetric between habitats, and (3) the case with unidirectional migration. The coexistence of competitors is more likely to occur when larval migration is weak.