Section: Evolutionary Biology
Topic: Evolution, Genetics/Genomics, Population biology

Conditions for maintaining and eroding pseudo-overdominance and its contribution to inbreeding depression

10.24072/pcjournal.224 - Peer Community Journal, Volume 3 (2023), article no. e8.

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Classical models that ignore linkage predict that deleterious recessive mutations should purge or fix within inbred populations, yet inbred populations often retain moderate to high segregating load. True overdominance could generate balancing selection strong enough to sustain inbreeding depression even within inbred populations, but this is considered rare. However, arrays of deleterious recessives linked in repulsion could generate appreciable pseudo-overdominance that would also sustain segregating load. We used simulations to explore how long pseudo-overdominant (POD) zones persist once created (e.g., by hybridization between populations fixed for alternative mildly deleterious mutations). Balanced haplotype loads, tight linkage, and moderate to strong cumulative selective effects all serve to maintain POD zones. Tight linkage is key, suggesting that such regions are most likely to arise and persist in low recombination regions (like inversions). Selection and drift unbalance the load, eventually eliminating POD zones, but this process is quite slow under strong pseudo-overdominance. Background selection accelerates the loss of weak POD zones but reinforces strong ones in inbred populations by disfavoring homozygotes. Models and empirical studies of POD dynamics within populations help us understand how POD zones may allow the load to persist, greatly affecting load dynamics and mating systems evolution

Published online:
DOI: 10.24072/pcjournal.224
Type: Research article

Abu-Awad, Diala 1, 2; Waller, Donald 3

1 Université Paris-Saclay, INRAE, CNRS, AgroParisTech, GQE—Le Moulon, Gif-sur-Yvette, France
2 Professorship for Population Genetics, Department of Life Science Systems, Technical University of Munich, Germany
3 Department of Botany, University of Wisconsin, Madison, WI USA
License: CC-BY 4.0
Copyrights: The authors retain unrestricted copyrights and publishing rights
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Abu-Awad, Diala; Waller, Donald. Conditions for maintaining and eroding pseudo-overdominance and its contribution to inbreeding depression. Peer Community Journal, Volume 3 (2023), article  no. e8. doi : 10.24072/pcjournal.224.

PCI peer reviews and recommendation, and links to data, scripts, code and supplementary information: 10.24072/pci.evolbiol.100531

Conflict of interest of the recommender and peer reviewers:
The recommender in charge of the evaluation of the article and the reviewers declared that they have no conflict of interest (as defined in the code of conduct of PCI) with the authors or with the content of the article.

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