Rapid Speciation via Parallel, Directional Selection on Regulatory Genetic Pathways

✍ Scribed by NORMAN A JOHNSON; ADAM H PORTER

• Book ID: 102611998
• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 351 KB
• Volume: 205
• Category: Article
• ISSN: 0022-5193
• DOI: 10.1006/jtbi.2000.2070

✦ Synopsis

Regulatory genetic pathways are ubiquitous in organisms and play a central role in the realization of the phenotype during development. We explored the proposition that these pathways can provide a plausible source of the epistatic variation that has been implicated in the evolution of postzygotic reproductive isolation. We modeled gene regulation as a matching function between the product of one locus and the promoter site of the next locus in the pathway, with binding strength determining the amount of product. When the phenotype is subject to parallel selection in a pair of independent populations, we "nd that the "tnesses of F and F hybrids often drop to very low values as the populations respond in genetically di!erent and incompatible ways. The simulations support the predictions of the analytical models. Hybrid "tness reduction occurs more often as the number of loci in the pathway increases, and as the binding site interactions become more complex. Less hybrid "tness reduction is seen when the populations start with imperfect binding in the pathway. In contrast, when we constructed the phenotype without gene regulation using multiplicative rules, isomorphic to the additive phenotype commonly assumed in evolutionary models, we found no appreciable F "tness reduction and only slight F "tness reduction. The interaction of genetic drift and mutation, even at very high rates, did not reduce hybrid "tness at all on the time-scales we considered. Clearly, the evolution of regulatory genetic pathways can play an important role in speciation, but much more empirical information is needed on the e!ect of allelic variability in regulatory site interactions before this role is fully understood.