Local frequency dependence and global coexistence

In sessile organisms such as plants, interactions occur locally so that imp ortant ecological aspects like frequency dependence are manifest within loc al neighborhoods. Using probabilistic cellular automata models, we investig ated how local frequency-dependent competition influenced whether two speci es could coexist. Individuals of the two species were randomly placed on a grid and allowed to interact according to local frequency-dependent rules. For four different frequency-dependent scenarios, the results indicated tha t over a broad parameter range the two species could coexist. Comparisons b etween explicit spatial simulations and the mean-field approximation indica te that coexistence occurs over a broader region in the explicit spatial si mulation. (C) 1999 Academic Press.