Population Genetics and Genome Evolution of Selfing Species

Abstract

The evolution of self‐fertilisation from outcrossing is one of the most frequent evolutionary transitions in hermaphrodite species of plants, animals and fungi. Accordingly, a large body of theoretical and empirical studies has been dedicated to understand the impact of selfing on population genetics and genome evolution. Compared to outcrossing, selfing reduces heterozygosity, effective recombination and migration rate and increases genetic drift. As a consequence, selfing species are expected to show reduced and more structured genetic diversity, genomic degradation and low adaptive potential because they should respond less efficiently to natural selection. Although selfing can have immediate advantages and be selected for, all detrimental genetic effects are thought to drive selfing lineages to extinction on the long run. Human activities (e.g. domestication and breeding, ecosystem alterations) can also induce mating system shifts that could potentially threaten long‐term population viability.

Key Concepts

  • The transition from outcrossing to selfing affects fundamental population genetics parameters that influence the evolutionary trajectory of populations and species.
  • Selfing increases homozygosity, which reveals recessive deleterious alleles causing inbreeding depression.
  • Selfing reduces the effective recombination, which increases genome‐wide linkage disequilibrium.
  • Selfing increases genetic structure by reducing gene flow.
  • Selfing reduces the effective population size, making selfing species less diverse and less efficient in responding to selection than outcrossing ones.
  • The outcome of selection in selfing species depends on the interplay among dominance level and selection strength of mutations and the initial conditions (new mutations or preexisting variation).
  • In selfing organisms, sexual conflicts and the spread of selfish genetic elements are attenuated.
  • Overall, the genome of selfing species is prone to the accumulation of deleterious mutations and to low rates of fixation of beneficial mutations, which should make selfing an evolutionary ‘dead‐end’ strategy.
  • The genetic consequences induced by self‐fertilisation have practical implications for human activities linked to the conservation and management of natural and cultivated resources.

Keywords: mating systems; selfing; effective population size; inbreeding depression; deleterious mutations; genetic diversity; adaptive potential; genomic conflicts; recombination; population structure

Figure 1. Genetic effects of self‐fertilisation compared to outcrossing mating.
Figure 2. Factors affecting genetic diversity and potential for adaptation in self‐fertilising species. Arrows represent cause–effect relations in a decreasing (blue) or increasing (red) sense. Ne is the species effective population size and is globally reduced by selfing.
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Further Reading

Glémin S and Galtier N (2012) Genome evolution in outcrossing versus selfing versus asexual species. In: Anisimova M (ed) Evolutionary Genomics Methods in Molecular Biology, pp. 311–335. New York City: Humana Press.

Hartfield M (2016) Evolutionary genetic consequences of facultative sex and outcrossing. Journal of Evolutionary Biology 29: 5–22.

Wright SI, Ness RW, Foxe JP and Barrett SCH (2008) Genomic consequences of outcrossing and selfing in plants. International Journal of Plant Sciences 169: 105–118.

Wright SI, Kalisz S and Slotte T (2013) Evolutionary consequences of self‐fertilization in plants. Proceedings of the Royal Society B: Biological Sciences 280: 20130133.

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Burgarella, Concetta, and Glémin, Sylvain(Jan 2017) Population Genetics and Genome Evolution of Selfing Species. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0026804]