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Reproduction through sex carries substantial costs, mainly becauseonly half of sexual adults produce offspring1. It has been theorizedthat these costs could be countered if sex allows sexual selection toclear the universal fitness constraint of mutation load2–4. Undersexual selection, competition between (usually) males and matechoice by (usually) females create important intraspecific filtersfor reproductive success, so that only a subset of males gainspaternity. If reproductive success under sexual selection is depend-ent on individual condition, which is contingent to mutation load,then sexually selected filtering through ‘genic capture’5could offsetthe costs of sex because it provides genetic benefits to populations.Here we test this theory experimentally by comparing whetherpopulations with histories of strong versus weak sexual selectionpurge mutation load and resist extinction differently. After evol-ving replicate populations of the flour beetleTribolium castaneumfor 6 to 7 years under conditions that differed solely in thestrengths of sexual selection, we revealed mutation load usinginbreeding. Lineages from populations that had previously experi-enced strong sexual selection were resilient to extinction and main-tained fitness under inbreeding, with some families continuing tosurvive after 20 generations of sib3sib mating. By contrast,lineages derived from populations that experienced weak or non-existent sexual selection showed rapid fitness declines underinbreeding, and all were extinct after generation 10. Multiplemutations across the genome with individually small effects canbe difficult to clear, yet sum to a significant fitness load; our find-ings reveal that sexual selection reduces this load, improving popu-lation viability in the face of genetic stress.only half of sexual adults produce offspring1. It has been theorizedthat these costs could be countered if sex allows sexual selection toclear the universal fitness constraint of mutation load2–4. Undersexual selection, competition between (usually) males and matechoice by (usually) females create important intraspecific filtersfor reproductive success, so that only a subset of males gainspaternity. If reproductive success under sexual selection is depend-ent on individual condition, which is contingent to mutation load,then sexually selected filtering through ‘genic capture’5could offsetthe costs of sex because it provides genetic benefits to populations.Here we test this theory experimentally by comparing whetherpopulations with histories of strong versus weak sexual selectionpurge mutation load and resist extinction differently. After evol-ving replicate populations of the flour beetleTribolium castaneumfor 6 to 7 years under conditions that differed solely in thestrengths of sexual selection, we revealed mutation load usinginbreeding. Lineages from populations that had previously experi-enced strong sexual selection were resilient to extinction and main-tained fitness under inbreeding, with some families continuing tosurvive after 20 generations of sib3sib mating. By contrast,lineages derived from populations that experienced weak or non-existent sexual selection showed rapid fitness declines underinbreeding, and all were extinct after generation 10. Multiplemutations across the genome with individually small effects canbe difficult to clear, yet sum to a significant fitness load; our find-ings reveal that sexual selection reduces this load, improving popu-lation viability in the face of genetic stress.Reproduction through sex carries substantial costs, mainly becauseonly half of sexual adults produce offspring1. It has been theorizedthat these costs could be countered if sex allows sexual selection toclear the universal fitness constraint of mutation load2–4. Undersexual selection, competition between (usually) males and matechoice by (usually) females create important intraspecific filtersfor reproductive success, so that only a subset of males gainspaternity. If reproductive success under sexual selection is depend-ent on individual condition, which is contingent to mutation load,then sexually selected filtering through ‘genic capture’5could offsetthe costs of sex because it provides genetic benefits to populations.Here we test this theory experimentally by comparing whetherpopulations with histories of strong versus weak sexual selectionpurge mutation load and resist extinction differently. After evol-ving replicate populations of the flour beetleTribolium castaneumfor 6 to 7 years under conditions that differed solely in thestrengths of sexual selection, we revealed mutation load usinginbreeding. Lineages from populations that had previously experi-enced strong sexual selection were resilient to extinction and main-tained fitness under inbreeding, with some families continuing tosurvive after 20 generations of sib3sib mating. By contrast,lineages derived from populations that experienced weak or non-existent sexual selection showed rapid fitness declines underinbreeding, and all were extinct after generation 10. Multiplemutations across the genome with individually small effects canbe difficult to clear, yet sum to a significant fitness load; our find-ings reveal that sexual selection reduces this load, improving popu-lation viability in the face of genetic stress.
Author(s): Lumley AJ, Michalczyk L, Kitson JJN, Spurgin LG, Morrison CA, Godwin JL, Dickinson ME, Martin OY, Emerson BC, Chapman T, Gage MJ
Publication type: Article
Publication status: Published
Journal: Nature
Year: 2015
Volume: 522
Issue: 7557
Pages: 470-473
Print publication date: 25/06/2015
Online publication date: 18/05/2015
Acceptance date: 18/03/2015
ISSN (print): 0028-0836
Publisher: Nature Publishing Group
URL: http://dx.doi.org/10.1038/nature14419
DOI: 10.1038/nature14419
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