  Current theories about mechanisms promoting species co-existence in diverse
communities assume that species only interact ecologically. Species are treated
as discrete evolutionary entities, even though abundant empirical evidence
indicates that patterns of gene flow such as selfing and hybridization
frequently occur in plant and animal groups. Here, we allow mating behavior to
respond to local species composition and abundance in a data-driven
meta-community model of species co-existence. While individuals primarily
out-cross, they also maintain some small capacity for selfing and
hybridization. Mating choice is treated as a 'fuzzy' behavior, determined by an
interaction between intrinsic properties affecting mate choice and extrinsic
properties of the local community, primarily the density and availability of
sympatric inter-fertile species. When mate choice is strongly limited, even low
survivorship of selfed offspring (<10%) can prevent extinction of rare species.
With increasing mate choice, low hybridization success rates (~20%) maintain
community level diversity for substantially longer periods of time. Given the
low species densities and high diversity of tropical tree communities, the
evolutionary costs of competition among sympatric congeneric species are
negligible because direct competition is infrequent. In diverse communities,
many species are chronically rare and thus vulnerable to stochastic extinction,
which occurs rapidly if species are completely reproductively isolated. By
incorporating fuzzy mating behavior into models of species co-existence, a more
realistic understanding of the extinction process can be developed. Fuzzy
mating strategies, potentially an important mechanism for rare species to
escape extinction and gain local adaptations, should be incorporated into
forest management strategies.
