| 1. |
- Bolund, Elisabeth, et al.
(författare)
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Reduced costs of reproduction in females mediate a shift from a male-biased to a female-biased lifespan in humans
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- The causes underlying sex differences in lifespan are strongly debated. While females commonly outlive males in humans, this is generally less pronounced in societies before the demographic transition to low mortality and fertility rates. Life-history theory suggests that reduced reproduction should benefit female lifespan when females pay higher costs of reproduction than males. Using unique longitudinal demographic records on 140,600 reproducing individuals from the Utah Population Database, we demonstrate a shift from male-biased to female-biased adult lifespans in individuals born before versus during the demographic transition. Only women paid a cost of reproduction in terms of shortened post-reproductive lifespan at high parities. Therefore, as fertility decreased over time, female lifespan increased, while male lifespan remained largely stable, supporting the theory that differential costs of reproduction in the two sexes result in the shifting patterns of sex differences in lifespan across human populations. Further, our results have important implications for demographic forecasts in human populations and advance our understanding of lifespan evolution.
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| 2. |
- Berg, Elena C., et al.
(författare)
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Kin but less than kind : within-group male relatedness does not increase female fitness in seed beetles
- 2019
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : ROYAL SOC. - 0962-8452 .- 1471-2954. ; 286:1910, s. 1471-2954
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Tidskriftsartikel (refereegranskat)abstract
- Theory maintains within-group male relatedness can mediate sexual conflict by reducing male-male. competition and collateral harm to females. We tested whether male relatedness can lessen female harm in the seed beetle Callosobruchus maculatus. Male relatedness did not influence female lifetime reproductive success or individual fitness across two different ecologically relevant scenarios of mating competition. However, male relatedness marginally improved female survival. Because male relatedness improved female-survival in late life when C. maculatus females are no longer producing offspring, our results do not provide support for the role of within-group male relatedness in mediating sexual conflict. The fact that male relatedness improves the post-reproductive part of the female life cycle strongly suggests that the effect is non-adaptive. We discuss adaptive and non-adaptive mechanisms that could result in reduced female harm in this and previous studies, and suggest that cognitive error is a likely explanation.
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| 3. |
- Berger, David, et al.
(författare)
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Intralocus Sexual Conflict and the Tragedy of the Commons in Seed Beetles
- 2016
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Ingår i: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 188:4, s. E98-E112
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Tidskriftsartikel (refereegranskat)abstract
- The evolution of male traits that inflict direct harm on females during mating interactions can result in a so-called tragedy of the commons, where selfish male strategies depress population viability. This tragedy of the commons can be magnified by intralocus sexual conflict (IaSC) whenever alleles that reduce fecundity when expressed in females spread in the population because of their benefits in males. We evaluated this prediction by detailed phenotyping of 73 isofemale lines of the seed beetle Callosobruchus maculatus. We quantified genetic variation in life history andmorphology, as well as associated covariance in male and female adult reproductive success. In parallel, we created replicated artificial populations of each line and measured their productivity. Genetic constraints limited independent trait expression in the sexes, and we identified several instances of sexually antagonistic covariance between traits and fitness, signifying IaSC. Population productivity was strongly positively correlated to female adult reproductive success but uncorrelated with male reproductive success. Moreover, male (female) phenotypic optima for several traits under sexually antagonistic selection were exhibited by the genotypes with the lowest (highest) population productivity. Our study forms a direct link between individuallevel sex-specific selection and population demography and places lifehistory traits at the epicenter of these dynamics.
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| 4. |
- Berger, David, et al.
(författare)
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Sexually antagonistic selection on genetic variation underlying both male and female same-sex sexual behavior
- 2016
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Ingår i: BMC Evolutionary Biology. - : Springer Science and Business Media LLC. - 1471-2148. ; 16
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Tidskriftsartikel (refereegranskat)abstract
- Intralocus sexual conflict, arising from selection for different alleles at the same locus in males and females, imposes a constraint on sex-specific adaptation. Intralocus sexual conflict can be alleviated by the evolution of sex-limited genetic architectures and phenotypic expression, but pleiotropic constraints may hinder this process. Here, we explored putative intralocus sexual conflict and genetic (co)variance in a poorly understood behavior with near male-limited expression. Same-sex sexual behaviors (SSBs) generally do not conform to classic evolutionary models of adaptation but are common in male animals and have been hypothesized to result from perception errors and selection for high male mating rates. However, perspectives incorporating sex-specific selection on genes shared by males and females to explain the expression and evolution of SSBs have largely been neglected.
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| 5. |
- Chen, Hwei -Yen, et al.
(författare)
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Evolution of male age-specific reproduction under differential risks and causes of death : males pay the cost of high female fitness
- 2016
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 29:4, s. 848-856
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Tidskriftsartikel (refereegranskat)abstract
- Classic theories of ageing evolution predict that increased extrinsic mortality due to an environmental hazard selects for increased early reproduction, rapid ageing and short intrinsic lifespan. Conversely, emerging theory maintains that when ageing increases susceptibility to an environmental hazard, increased mortality due to this hazard can select against ageing in physiological condition and prolong intrinsic lifespan. However, evolution of slow ageing under high-condition-dependent mortality is expected to result from reallocation of resources to different traits and such reallocation may be hampered by sex-specific trade-offs. Because same life-history trait values often have different fitness consequences in males and females, sexually antagonistic selection can preserve genetic variance for lifespan and ageing. We previously showed that increased condition-dependent mortality caused by heat shock leads to evolution of long-life, decelerated late-life mortality in both sexes and increased female fecundity in the nematode, Caenorhabditis remanei. Here, we used these cryopreserved lines to show that males evolving under heat shock suffered from reduced early-life and net reproduction, while mortality rate had no effect. Our results suggest that heat-shock resistance and associated long-life trade-off with male, but not female, reproduction and therefore sexually antagonistic selection contributes to maintenance of genetic variation for lifespan and fitness in this population.
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| 6. |
- Hooper, Amy K., et al.
(författare)
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Ontogenetic timing as a condition-dependent life history trait : High-condition males develop quickly, peak early, and age fast
- 2017
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Ingår i: Evolution. - : WILEY. - 0014-3820 .- 1558-5646. ; 71:3, s. 671-685
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Tidskriftsartikel (refereegranskat)abstract
- Within-population variation in ageing remains poorly understood. In males, condition-dependent investment in secondary sexual traits may incur costs that limit ability to invest in somatic maintenance. Moreover, males often express morphological and behavioral secondary sexual traits simultaneously, but the relative effects on ageing of investment in these traits remain unclear. We investigated the condition dependence of male life history in the neriid fly Telostylinus angusticollis. Using a fully factorial design, we manipulated male early-life condition by varying nutrient content of the larval diet and, subsequently, manipulated opportunity for adult males to interact with rival males. We found that high-condition males developed more quickly and reached their reproductive peak earlier in life, but also experienced faster reproductive ageing and died sooner than low-condition males. By contrast, interactions with rival males reduced male lifespan but did not affect male reproductive ageing. High-condition in early life is therefore associated with rapid ageing in T. angusticollis males, even in the absence of damaging male-male interactions. Our results show that abundant resources during the juvenile phase are used to expedite growth and development and enhance early-life reproductive performance at the expense of late-life performance and survival, demonstrating a clear link between male condition and ageing.
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| 7. |
- Kotrschal, Alexander, et al.
(författare)
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Positive genetic correlation between brain size and sexual traits in male guppies artificially selected for brain size
- 2015
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 28:4, s. 841-850
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Tidskriftsartikel (refereegranskat)abstract
- Brain size is an energetically costly trait to develop and maintain. Investments into other costly aspects of an organism's biology may therefore place important constraints on brain size evolution. Sexual traits are often costly and could therefore be traded off against neural investment. However, brain size may itself be under sexual selection through mate choice on cognitive ability. Here, we use guppy (Poecilia reticulata) lines selected for large and small brain size relative to body size to investigate the relationship between brain size, a large suite of male primary and secondary sexual traits, and body condition index. We found no evidence for trade-offs between brain size and sexual traits. Instead, larger-brained males had higher expression of several primary and precopulatory sexual traits - they had longer genitalia, were more colourful and developed longer tails than smaller-brained males. Larger-brained males were also in better body condition when housed in single-sex groups. There was no difference in post-copulatory sexual traits between males from the large- and small-brained lines. Our data do not support the hypothesis that investment into sexual traits is an important limiting factor to brain size evolution, but instead suggest that brain size and several sexual traits are positively genetically correlated.
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| 8. |
- Lind, Martin I., et al.
(författare)
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Evolution of differential maternal age effects on male and female offspring development and longevity
- 2015
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Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 29:1, s. 104-110
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Tidskriftsartikel (refereegranskat)abstract
- Maternal age effects on life-history traits, including longevity, are widespread and can be seen as a manifestation of ageing. However, little is known about how maternal life span may influence the maternal age effect. At a given chronological age, a long-lived parent may be at a younger biological age than a short-lived parent and thus has a less severe parental age effect. However, earlier work using experimentally evolved short- and long-lived lines did not support this hypothesis. We scored developmental time and longevity of 14995 individual seed beetles, Callosobruchus maculatus derived from replicate short-lived and long-lived lines created via artificial selection on male life span. Offspring from older mothers had shorter life span, which is consistent with most of the literature. We found support for the hypothesis that detrimental maternal age effects evolve to be weaker under selection for long life span. However, this finding was only apparent in males, suggesting that maternal age affects male and female offspring differently. These results suggest that sex-dependent parental age effects should be incorporated in the studies of longevity and ageing evolution and that selection on one sex can cause evolution of parental age effects in the other sex.
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| 9. |
- Lind, Martin I., et al.
(författare)
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Rapamycin additively extends lifespan in short- and long-lived lines of the nematode Caenorhabditis remanei
- 2017
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Ingår i: Experimental Gerontology. - : Elsevier BV. - 0531-5565 .- 1873-6815. ; 90, s. 79-82
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Tidskriftsartikel (refereegranskat)abstract
- Despite tremendous progress in finding genes that, when manipulated, affects lifespan, little is known about the genetics underlying natural variation in lifespan. While segregating genetic variants for lifespan has been notoriously difficult to find in genome-wide association studies (GWAS), a complementary approach is to manipulate key genetic pathways in lines that differ in lifespan. If these candidate pathways are down regulated in long-lived lines, these lines can be predicted to respond less to pharmaceutical down-regulation of these pathways than short-lived lines. Experimental studies have identified the nutrient-sensing pathway TOR as a key regulator of lifespan in model organisms, and this pathway can effectively be down regulated using the drug rapamycin, which extends lifespan in all tested species. We expose short-and long-lived lines of the nematode Caenorhabditis remanei to rapamycin, and investigate if long-lived lines, which are hypothesized to already have down-regulated TOR signaling, respond less to rapamycin. We found no interaction between line and rapamycin treatment, since rapamycin extended lifespan independent of the intrinsic lifespan of the lines. This shows that rapamycin is equally effective on long and short-lived lines, and suggests that the evolution of long life may involve more factors that down-regulation of TOR.
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| 10. |
- Lind, Martin I., et al.
(författare)
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Sex-specific Tradeoffs With Growth and Fitness Following Life-span Extension by Rapamycin in an Outcrossing Nematode, Caenorhabditis remanei
- 2016
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Ingår i: The journals of gerontology. Series A, Biological sciences and medical sciences. - : Oxford University Press (OUP). - 1079-5006 .- 1758-535X. ; 71:7, s. 882-890
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Tidskriftsartikel (refereegranskat)abstract
- Rapamycin inhibits the nutrient-sensing TOR pathway and extends life span in a wide range of organisms. Although life-span extension usually differs between the sexes, the reason for this is poorly understood. Because TOR influences growth, rapamycin likely affects life-history traits such as growth and reproduction. Sexes have different life-history strategies, and theory predicts that they will resolve the tradeoffs between growth, reproduction, and life span differently. Specifically, in taxa with female-biased sexual size dimorphism, reduced growth may have smaller effects on male fitness. We investigated the effects of juvenile, adult, or life-long rapamycin treatment on growth, reproduction, life span, and individual fitness in the outcrossing nematode Caenorhabditis remanei. Life-long exposure to rapamycin always resulted in the strongest response, whereas postreproductive exposure did not affect life span. Although rapamycin resulted in longer life span and smaller size in males, male individual fitness was not affected. In contrast, size and fitness were negatively affected in females, whereas life span was only extended under high rapamycin concentrations. Our results support the hypothesis that rapamycin affects key life-history traits in a sex-specific manner. We argue that the fitness cost of life-span extension will be sex specific and propose that the smaller sex generally pay less while enjoying stronger life-span increase.
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