Spontaneous genetic clustering in populations of competing organisms
  We introduce and analyse an individual-based evolutionary model, in which a population of genetically diverse organisms compete with each other for limited resources. Through theoretical analysis and stochastic simulations, we show that the model exhibits a pattern-forming instability which is highly amplified by the effects of demographic noise, leading to the spontaneous formation of genotypic clusters. This mechanism supports the thesis that stochasticity has a central role in the formation and coherence of species. 
Tim Rogers, Alan J. McKane and Axel G. Rossberg
q-bio.PE cond-mat.stat-mech physics.bio-ph