Inbreeding depresses sperm competitiveness, but not fertilization or mating success in male Tribolium castaneum

Michalczyk, L, Martin, OY, Millard, AL, Emerson, BC and Gage, MJG (2010) Inbreeding depresses sperm competitiveness, but not fertilization or mating success in male Tribolium castaneum. Proceedings of the Royal Society B: Biological Sciences, 277 (1699). pp. 3483-3491. ISSN 0962-8452

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Abstract

As populations decline to levels where reproduction among close genetic relatives becomes more probable, subsequent increases in homozygous recessive deleterious expression and/or loss of heterozygote advantage can lead to inbreeding depression. Here, we measure how inbreeding across replicate lines of the flour beetle Tribolium castaneum impacts on male reproductive fitness in the absence or presence of male–male competition. Effects on male evolution from mating pattern were removed by enforcing monogamous mating throughout. After inbreeding across eight generations, we found that male fertility in the absence of competition was unaffected. However, we found significant inbreeding depression of sperm competitiveness: non-inbred males won 57 per cent of fertilizations in competition, while inbred equivalents only sired 42 per cent. We also found that the P2 ‘offence’ role in sperm competition was significantly more depressed under inbreeding than sperm ‘defence’ (P1). Mating behaviour did not explain these differences, and there was no difference in the viability of offspring sired by inbred or non-inbred males. Sperm length variation was significantly greater in the ejaculates of inbred males. Our results show that male ability to achieve normal fertilization success was not depressed under strong inbreeding, but that inbreeding depression in these traits occurred when conditions of sperm competition were generated.

Item Type: Article
Faculty \ School: Faculty of Science > School of Biological Sciences
University of East Anglia > Faculty of Science > Research Centres > Centre for Ecology, Evolution and Conservation
University of East Anglia > Faculty of Science > Research Groups > Organisms and the Environment
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Depositing User: Deborah Clemitshaw
Date Deposited: 18 May 2011 11:13
Last Modified: 24 Aug 2018 17:30
URI: https://ueaeprints.uea.ac.uk/id/eprint/30772
DOI: 10.1098/rspb.2010.0514

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