| 1. |
- Alavioon, Ghazal, et al.
(författare)
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Haploid selection within a single ejaculate increases offspring fitness
- 2017
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; :30, s. 8053-8058
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Tidskriftsartikel (refereegranskat)abstract
- An inescapable consequence of sex in eukaryotes is the evolution of a biphasic life cycle with alternating diploid and haploid phases. The occurrence of selection during the haploid phase can have far-reaching consequences for fundamental evolutionary processes including the rate of adaptation, the extent of inbreeding depression, and the load of deleterious mutations, as well as for applied research into fertilization technology. Although haploid selection is well established in plants, current dogma assumes that in animals, intact fertile sperm within a single ejaculate are equivalent at siring viable offspring. Using the zebrafish Danio rerio, we show that selection on phenotypic variation among intact fertile sperm within an ejaculate affects offspring fitness. Longer-lived sperm sired embryos with increased survival and a reduced number of apoptotic cells, and adult male offspring exhibited higher fitness. The effect on embryo viability was carried over into the second generation without further selection and was equally strong in both sexes. Sperm pools selected by motile phenotypes differed genetically at numerous sites throughout the genome. Our findings clearly link within-ejaculate variation in sperm phenotype to offspring fitness and sperm genotype in a vertebrate and have major implications for adaptive evolution.
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| 2. |
- Alavioon, Ghazal, et al.
(författare)
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Selection for longer lived sperm within ejaculate reduces reproductive ageing in offspring
- 2019
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Ingår i: Evolution Letters. - : Oxford University Press (OUP). - 2056-3744. ; 3:2, s. 198-206
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Tidskriftsartikel (refereegranskat)abstract
- Males produce numerous sperm in a single ejaculate that greatly outnumber their potential egg targets. Recent studies found that phenotypic and genotypic variation among sperm in a single ejaculate of a male affects the fitness and performance of the resulting offspring. Specifically, within-ejaculate sperm selection for sperm longevity increased the performance of the resulting offspring in several key life-history traits in early life. Because increased early-life reproductive performance often correlates with rapid ageing, it is possible that within-ejaculate sperm selection increases early-life fitness at the cost of accelerated senescence. Alternatively, within-ejaculate sperm selection could improve offspring quality throughout the life cycle, including reduced age-specific deterioration. We tested the two alternative hypotheses in an experimental setup using zebrafish Danio rerio. We found that within-ejaculate sperm selection for sperm longevity reduced age-specific deterioration of fecundity and offspring survival but had no effect on fertilization success in males. Remarkably, we found an opposing effect of within-ejaculate sperm selection on female fecundity, where selection for sperm longevity resulted in increased early-life performance followed by a slow decline, while females sired by unselected sperm started low but increased their fecundity with age. Intriguingly, within-ejaculate sperm selection also reduced the age-specific decline in fertilization success in females, suggesting that selection for sperm longevity improves at least some aspects of female reproductive ageing. These results demonstrate that within-ejaculate variation in sperm phenotype contributes to individual variation in animal life histories in the two sexes and may have important implications for assisted fertilization programs in livestock and humans.
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| 3. |
- Maklakov, Alex A, et al.
(författare)
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Antagonistically pleiotropic allele increases lifespan and late-life reproduction at the cost of early-life reproduction and individual fitness
- 2017
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : ROYAL SOC. - 0962-8452 .- 1471-2954. ; 284:1856
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Tidskriftsartikel (refereegranskat)abstract
- Evolutionary theory of ageing maintains that increased allocation to early-life reproduction results in reduced somatic maintenance, which is predicted to compromise longevity and late-life reproduction. This prediction has been challenged by the discovery of long-lived mutants with no loss of fecundity. The first such long-lived mutant was found in the nematode worm Caenorhabditis elegans. Specifically, partial loss-of-function mutation in the age-1 gene, involved in the nutrient-sensing insulin/insulin-like growth factor signalling pathway, confers longevity, as well as increased resistance to pathogens and to temperature stress without appreciable fitness detriment. Here, we show that the long-lived age-1(hx546) mutant has reduced fecundity and offspring production in early-life, but increased fecundity, hatching success, and offspring production in late-life compared with wild-type worms under standard conditions. However, reduced early-life performance of long-lived mutant animals was not fully compensated by improved performance in late-life and resulted in reduced individual fitness. These results suggest that the age-1(hx546) allele has opposing effects on early-life versus late-life fitness in accordance with antagonistic pleiotropy (AP) and disposable soma theories of ageing. These findings support the theoretical conjecture that experimental studies based on standing genetic variation underestimate the importance of AP in the evolution of ageing.
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