What role does natural selection play in speciation?

Philos Trans R Soc Lond B Biol Sci. 2010 Jun 12;365(1547):1825-40. doi: 10.1098/rstb.2010.0001.


If distinct biological species are to coexist in sympatry, they must be reproductively isolated and must exploit different limiting resources. A two-niche Levene model is analysed, in which habitat preference and survival depend on underlying additive traits. The population genetics of preference and viability are equivalent. However, there is a linear trade-off between the chances of settling in either niche, whereas viabilities may be constrained arbitrarily. With a convex trade-off, a sexual population evolves a single generalist genotype, whereas with a concave trade-off, disruptive selection favours maximal variance. A pure habitat preference evolves to global linkage equilibrium if mating occurs in a single pool, but remarkably, evolves to pairwise linkage equilibrium within niches if mating is within those niches--independent of the genetics. With a concave trade-off, the population shifts sharply between a unimodal distribution with high gene flow and a bimodal distribution with strong isolation, as the underlying genetic variance increases. However, these alternative states are only simultaneously stable for a narrow parameter range. A sharp threshold is only seen if survival in the 'wrong' niche is low; otherwise, strong isolation is impossible. Gene flow from divergent demes makes speciation much easier in parapatry than in sympatry.

Publication types

  • Review

MeSH terms

  • Animals
  • Biological Evolution
  • Ecosystem
  • Female
  • Gene Flow
  • Genetic Speciation*
  • Genetics, Population
  • Linkage Disequilibrium
  • Male
  • Models, Genetic*
  • Mutation
  • Recombination, Genetic
  • Reproduction / genetics
  • Selection, Genetic*