Evol Ecol Res 11: 1251-1258 (2009)     Full PDF if your library subscribes.

Competition enhances spatial genetic differentiation

Esa Ranta1†, Lars A. Bach2, Veijo Kaitala1, Mats Björklund3 and Per Lundberg2

1Department of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland, 2Department of Theoretical Ecology, Lund University, Lund, Sweden and 3Animal Ecology/Department of Ecology and Evolution, Uppsala University, Uppsala, Sweden

Correspondence: L.A. Bach, Department of Theoretical Ecology, Ecology Building, Lund University, Sölvegatan 37, SE-22362 Lund, Sweden.
e-mail: lars.bach@teorekol.lu.se


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.

Keywords: community genetics, competition, FST, Lotka-Volterra, spatial structure, species diversity, stepping-stone.

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