Download Recombination and epistasis facilitate introgressive hybridization

Evolutionary Ecology Research, 2010, 12: 523–544
Recombination and epistasis facilitate introgressive
hybridization across reproductively isolated
populations: a gamete-based simulation
Yoshinari Tanaka
Center for Environmental Risk, National Institute for Environmental Studies, Tsukuba, Japan
ABSTRACT
Questions: Why can invasive species sometimes genetically contaminate closely related
indigenous species by introgressive hybridization, resisting the post-zygotic isolating mechanism? How do recombination rates and epistasis among incompatibility genes, and the
number of loci affect the introgression?
Features of models: The individual-based model and gamete-based model, which tracks
changes in the number of invasive genes per gamete due to selection and recombination by
assuming random arrangement of genes within gamete.
Range of key variables: The recombination rate between adjacent loci ranges from 0 to 0.4.
The epistatic effect between loci is measured by the exponent of the geometric function
of heterozygosities representing individual fitness. It ranges from 1 (additive) to 4 (strong
epistasis). The number of loci is set to 2–10 for the gamete-based model.
Conclusions: Provided that the number of loci is not very small and the fitness of the F1
hybrid is not extremely low, complete genetic replacement by introgressive hybridization is
accelerated by an increase in rates of total recombination across all loci and by the epistatic
fitness effect among incompatibility loci.
Keywords: Dobzhansky-Mueller model, epistasis, gamete-based model,
introgressive hybridization, multi-locus underdominance, post-zygotic isolation.
INTRODUCTION
Introgressive hybridization by anthropogenic transference of exotic species brings about
genetic contamination of endemic species, which, in some extreme cases, leads to genetic
extinction of the endemic population by complete genetic assimilation or replacement by
the invasive population (Levin et al., 1995; Rieseberg and Gerber, 1995; Rhymer and Simberloff, 1996; Epifanio and
Nielsen, 2000; Mallet, 2005).
Apart from ecological factors such as predation and competition by biotic invasion,
hybridization of endemic species with closely related invading species or subspecies poses
Correspondence: Y. Tanaka, Center for Environmental Risk, National Institute for Environmental Studies,
Onogawa 16-2, Tsukuba, Ibaraki 305-8506, Japan. e-mail: [email protected]
Consult the copyright statement on the inside front cover for non-commercial copying policies.
© 2010 Yoshinari Tanaka
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