Selection in males purges the mutation load on female fitness

Theory predicts that the ability of selection and recombination to purge mutation load is enhanced if selection against deleterious genetic variants operates more strongly in males than females. However, direct empirical support for this tenet is limited, in part because traditional quantitative genetic approaches allow dominance and intermediate-frequency polymorphisms to obscure the effects of the many rare and partially recessive deleterious alleles that make up the main part of a population's mutation load. Here, we exposed the partially recessive genetic load of a population of Callosobruchus maculatus seed beetles via successive generations of inbreeding, and quantified its effects by measuring heterosis—the increase in fitness experienced when masking the effects of deleterious alleles by heterozygosity—in a fully factorial sex-specific diallel cross among 16 inbred strains. Competitive lifetime reproductive success (i.e., fitness) was measured in male and female outcrossed F1s as well as inbred parental “selfs,” and we estimated the 4 × 4 male-female inbred-outbred genetic covariance matrix for fitness using Bayesian Markov chain Monte Carlo simulations of a custom-made general linear mixed effects model. We found that heterosis estimated independently in males and females was highly genetically correlated among strains, and that heterosis was strongly negatively genetically correlated to outbred male, but not female, fitness. This suggests that genetic variation for fitness in males, but not in females, reflects the amount of (partially) recessive deleterious alleles segregating at mutation-selection balance in this population. The population's mutation load therefore has greater potential to be purged via selection in males. These findings contribute to our understanding of the prevalence of sexual reproduction in nature and the maintenance of genetic variation in fitness-related traits

Sex-specific mitonuclear epistasis and the evolution of mitochondrial bioenergetics, ageing, and life history in seed beetles

The role of mitochondrial DNA for the evolution of life-history traits remains debated. We examined mitonuclear effects on the activity of the multisubunit complex of the electron transport chain (ETC) involved in oxidative phosphorylation (OXPHOS) across lines of the seed beetle Acanthoscelides obtectus selected for a short (E) or a long (L) life for more than >160 generations. We constructed and phenotyped mitonuclear introgression lines, which allowed us to assess the independent effects of the evolutionary history of the nuclear and the mitochondrial genome. The nuclear genome was responsible for the largest share of divergence seen in ageing. However, the mitochondrial genome also had sizeable effects, which were sex-specific and expressed primarily as epistatic interactions with the nuclear genome. The effects of mitonuclear disruption were largely consistent with mitonuclear coadaptation. Variation in ETC activity explained a large proportion of variance in ageing and life-history traits and this multivariate relationship differed somewhat between the sexes. In conclusion, mitonuclear epistasis has played an important role in the laboratory evolution of ETC complex activity, ageing, and life histories and these are closely associated. The mitonuclear architecture of evolved differences in life-history traits and mitochondrial bioenergetics was sex-specific.The final publication is available at Evolution (N Y). 2017;71(2):274–88. [http://ibiss-r.rcub.bg.ac.rs/123456789/2600]Evolution (2016

The consequences of sexual selection in well-adapted and maladapted populations of bean beetles.

Whether sexual selection generally promotes or impedes population persistence remains an open question. Intralocus sexual conflict (IaSC) can render sexual selection in males detrimental to the population by increasing the frequency of alleles with positive effects on male reproductive success but negative effects on female fecundity. Recent modeling based on fitness landscape theory, however, indicates that the relative impact of IaSC may be reduced in maladapted populations and that sexual selection therefore might promote adaptation when it is most needed. Here, we test this prediction using bean beetles that had undergone 80 generations of experimental evolution on two alternative host plants. We isolated and assessed the effect of maladaptation on sex-specific strengths of selection and IaSC by cross-rearing the two experimental evolution regimes on the alternative hosts and estimating within-population genetic (co)variance for fitness in males and females. Two key predictions were upheld: males generally experienced stronger selection compared to females and maladaptation increased selection in females. However, maladaptation consistently decreased male-bias in the strength of selection and IaSC was not reduced in maladapted populations. These findings imply that sexual selection can be disrupted in stressful environmental conditions, thus reducing one of the potential benefits of sexual reproduction in maladapted populations.This is the peer reviewed version of the following article: Martinossi-Allibert I, Savković U, Đorđević M, Arnqvist G, Stojković B, Berger D. The consequences of sexual selection in well-adapted and maladapted populations of bean beetles, which has been published in final form at [https://doi.org/10.1111/evo.13412]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving

Increasing body mass index at diagnosis of diabetes in young adult people during 1983-1999 in the Diabetes Incidence Study in Sweden (DISS).

Objective. To study trends in body mass index (BMI) at diagnosis of diabetes in all young Swedish adults in the age range of 15-34 years registered in a nation-based registry. Design. The BMI was assessed at diagnosis in diabetic patients 15-34 years of age at diagnosis, for a period of 17 years (1983-1999). Islet cell antibodies (ICA) were measured during three periods (1987-1988, 1992-1993 and 1998-1999). Setting. A nationwide study (Diabetes Incidence Study in Sweden). Subjects. A total of 4727 type 1 and 1083 type 2 diabetic patients. Main outcome measures. Incidence-year specific BMI adjusted for age, gender and time of diagnosis (month). Results. Body mass index at diagnosis increased significantly both in type 1 (21.4 ± 3.6 to 22.5 ± 4.0; P < 0.0001) and in type 2 (27.4 ± 6.8 to 32.0 ± 6.0; P < 0.0001) diabetic patients, also when adjusted for age, gender and month of diagnosis. A similar significant increase in BMI was found in type 1 diabetic patients and in type 2 diabetic patients in the periods 1987-1988, 1992-1993 and 1998-1999; years when ICA were assessed and considered in the classification of diabetes. Despite this increase in BMI, there was no increase in the incidence of diabetes in young-adult people in Sweden. Conclusion. Body mass index at diagnosis of diabetes in subjects 15-34 years of age has substantially increased during 1983-1999 in Sweden when adjusted for age, gender and month of diagnosis

Helicobacter pylori Adapts to Chronic Infection and Gastric Disease via pH-Responsive BabA-Mediated Adherence

International audienceThe BabA adhesin mediates high-affinity binding of Helicobacter pylori to the ABO blood group antigen-glycosylated gastric mucosa. Here we show that BabA is acid responsive-binding is reduced at low pH and restored by acid neutralization. Acid responsiveness differs among strains; often correlates with different intragastric regions and evolves during chronic infection and disease progression; and depends on pH sensor sequences in BabA and on pH reversible formation of high-affinity binding BabA multimers. We propose that BabA's extraordinary reversible acid responsiveness enables tight mucosal bacterial adherence while also allowing an effective escape from epithelial cells and mucus that are shed into the acidic bactericidal lumen and that bio-selection and changes in BabA binding properties through mutation and recombination with babA-related genes are selected by differences among individuals and by changes in gastric acidity over time. These processes generate diverse H. pylori subpopulations, in which BabA's adaptive evolution contributes to H. pylori persistence and overt gastric disease

Sexual selection and intersexual conflicts in water striders

Diss. (sammanfattning) Umeå : Umeå universitet, 1992, härtill 8 uppsatserdigitalisering@um

Sex ratio bias leads to the evolution of sex role reversal in honey locust beetles

The reversal of conventional sex roles was enigmatic to Darwin, who suggested that it may evolve when sex ratios are female biased [1]. Here we present direct evidence confirming Darwin’s hypothesis. We investigated mating system evolution in a sex-role-reversed beetle (Megabruchidius dorsalis) using experimental evolution under manipulated sex ratios and food regimes. In female-biased populations, where reproductive competition among females was intensified, females evolved to be more attractive and the sex roles became more reversed. Interestingly, female-specific mating behavior evolved more rapidly than male-specific mating behavior. We show that sexual selection due to reproductive competition can be strong in females and can target much the same traits as in males of species with conventional mating systems. Our study highlights two central points: the role of ecology in directing sexual selection and the role that females play in mating system evolution

Sexual selection and intersexual conflicts in water striders

Diss. (sammanfattning) Umeå : Umeå universitet, 1992, härtill 8 uppsatserdigitalisering@um

Larger genomes show improved buffering of adult fitness against environmental stress in seed beetles

Our general understanding of the evolution of genome size (GS) is incomplete, and it has long been clear that GS does not reflect organismal complexity. Here, we assess the hypothesis that larger genomes may allow organisms to better cope with environmental variation. It is, for example, possible that genome expansion due to proliferation of transposable elements or gene duplications may affect the ability to regulate and fine-tune transcriptional profiles. We used 18 populations of the seed beetle Callosobruchus maculatus, which differ in GS by up to 4.5%, and exposed adults and juveniles to environmental stress in a series of experiments where stage-specific fitness was assayed. We found that populations with larger genomes were indeed better buffered against environmental stress for adult, but not for juvenile, fitness. The genetic correlation across populations between GS and canalization of adult fitness is consistent with a role for natural selection in the evolution of GS