Evol Ecol Res 9: 51-69 (2007)     Full PDF if your library subscribes.

Delayed evolutionary branching in small populations

David Claessen,1* Jens Andersson,2‡ Lennart Persson2 and André M. de Roos1

1Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, PO Box 94084, 1090 GB Amsterdam, The Netherlands and  2Department of Ecology and Environmental Science, Umeå University, SE-90187 Umeå, Sweden

Author to whom all correspondence should be addressed.
e-mail: david.claessen@ens.fr


Question: How is the process of evolutionary branching influenced by demographic stochasticity?

Mathematical methods: Adaptive dynamics of (i) a simple consumer-resource model and (ii) an analogous but individual-based model with finite population size.

Key assumptions: Consumers have access to two habitats with dynamic resources. The fraction of time spent in each habitat is the evolving trait. System size influences absolute population size and hence demographic stochasticity but not the expected population densities. Reproduction is asexual.

Predictions: Absolute population size is an ecological factor that controls the outcome of evolutionary dynamics by modifying the level of demographic stochasticity. Small populations are predicted to remain monomorphic generalists while large populations are predicted to split evolutionarily into specialized sub-populations. Underlying the delayed or absent evolutionary branching in small populations are (i) random genetic drift and (ii) extinction of incipient branches due to near-neutral stability.

Keywords: adaptive dynamics, demographic stochasticity, evolutionary branching, extinction, finite population size, incipient species, random genetic drift.

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