What role does natural selection play in speciation? Journal Article

Author(s): Barton, Nicholas H
Article Title: What role does natural selection play in speciation?
Affiliation IST Austria
Abstract: 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.
Keywords: Animals; Gene Flow; Selection, Genetic; Female; Models, Genetic; Genetics, Population; Male; Mutation; Reproduction; Recombination, Genetic; Evolution; Linkage Disequilibrium; Ecosystem; Genetic Speciation
Journal Title: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
Volume: 365
Issue 1547
ISSN: 0962-8436
Publisher: Royal Society, The  
Date Published: 2010-06-12
Start Page: 1825
End Page: 1840
DOI: 10.1098/rstb.2010.0001
Notes: The author thanks the Werner-Gren Foundation and the Royal Swedish Academy of Sciences for organizing the symposium on the ‘Origin of Species’. He also thanks Reinhard Bürger, and two anonymous referees, for their helpful comments.
Open access: no