Competition enhances spatial genetic differentiation

Questions: How does the number of species in a community affect the level of genetic diversity of its constituent species? What is the relation between competitive interactions and the spatial distribution of genetic variation? When spatially structured, how is the genetic differentiation among subpopulations affected by competition and size of the community? Model features and key assumptions: A model combining one-locus two-allele genetics with density-dependent regulation in population renewal (Ricker function) and demographic stochasticity is extended to incorporate S-species Lotka-Volterra competition. The system is embedded into a spatial context where 1000 populations are connected with stepping-stone dispersal. Beginning from random genotype composition, the system is simulated and the resulting community composition and genetic diversity across space are recorded. Conclusions: Genetic differentiation in the ensemble increases with the number of competing species in the community (0.30 +/- 0.13, normalized coefficient with 95% confidence limit) and with the intensity of pair-wise competition (0.20 +/- 0.05) but most strongly with their interaction (0.62 +/- 0.22). Although the system-wide differentiation increases, one finds that the process leads to local paucity of genotypes and hence a negative correlation between species diversity and local genetic diversity