ORCID Profile
0000-0003-3870-2932
Current Organisation
Vanderbilt University Medical Center
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: The Royal Society
Date: 04-11-2020
Abstract: High-quality developmental environments often improve in idual performance into adulthood, but allocating toward early life traits, such as growth, development rate and reproduction, may lead to trade-offs with late-life performance. It is, therefore, uncertain how a rich developmental environment will affect the ageing process (senescence), particularly in wild insects. To investigate the effects of early life environmental quality on insect life-history traits, including senescence, we reared larval antler flies ( Protopiophila litigata ) on four diets of varying nutrient concentration, then recorded survival and mating success of adult males released in the wild. Declining diet quality was associated with slower development, but had no effect on other life-history traits once development time was accounted for. Fast-developing males were larger and lived longer, but experienced more rapid senescence in survival and lower average mating rate compared to slow developers. Ultimately, larval diet, development time and body size did not predict lifetime mating success. Thus, a rich environment led to a mixture of apparent benefits and costs, mediated by development time. Our results indicate that ‘silver spoon' effects can be complex and that development time mediates the response of adult life-history traits to early life environmental quality.
Publisher: Cold Spring Harbor Laboratory
Date: 11-07-2019
DOI: 10.1101/697581
Abstract: Reproduction between in iduals from different ancestral populations creates genetically admixed offspring. Admixture can have positive and negative impacts on in idual health, feeding back to population health. Historical and forced migrations, and recent mobility, have brought formerly disparate populations of humans together. Here we sought to better understand how temporal changes in genetic admixture influence levels of heterozygosity and health outcomes. We evaluated variation in ancestry over 100 birth years in 35,842 in iduals from a genetic database linked to health records in a population in the Southeastern United States. Analysis of 2,678 ancestrally informative markers revealed increased admixture and heterozygosity for all clinically-defined race groups since 1990. Most groups also exhibited increasing long-range linkage disequilibrium over time. A phenome-wide association study of clinical outcomes detected protective associations with female reproductive disorders and increased risk for diseases with links to autoimmunity dysfunction. These mixed effects have important ramifications for human health.
Publisher: Oxford University Press (OUP)
Date: 2011
Publisher: Wiley
Date: 05-05-2011
Publisher: Oxford University Press (OUP)
Date: 25-11-2019
Abstract: Dietary restriction (DR) is a well-established intervention to extend lifespan across taxa. Recent studies suggest that DR-driven lifespan extension can be cost-free, calling into question a central tenant of the evolutionary theory of aging. Nevertheless, boosting parental longevity can reduce offspring fitness. Such intergenerational trade-offs are often ignored but can account for the “missing costs” of longevity. Here, we use the nematode Caenorhabditis remanei to test for effects of DR by fasting on fitness of females and their offspring. Females deprived of food for 6 days indeed had increased fecundity, survival, and stress resistance after re-exposure to food compared with their counterparts with constant food access. However, offspring of DR mothers had reduced early and lifetime fecundity, slower growth rate, and smaller body size at sexual maturity. These findings support the direct trade-off between investment in soma and gametes challenging the hypothesis that increased somatic maintenance and impaired reproduction can be decoupled.
Publisher: Proceedings of the National Academy of Sciences
Date: 08-04-2013
Abstract: Compelling evidence from many animal taxa indicates that male genitalia are often under postcopulatory sexual selection for characteristics that increase a male’s relative fertilization success. There could, however, also be direct precopulatory female mate choice based on male genital traits. Before clothing, the nonretractable human penis would have been conspicuous to potential mates. This observation has generated suggestions that human penis size partly evolved because of female choice. Here we show, based upon female assessment of digitally projected life-size, computer-generated images, that penis size interacts with body shape and height to determine male sexual attractiveness. Positive linear selection was detected for penis size, but the marginal increase in attractiveness eventually declined with greater penis size (i.e., quadratic selection). Penis size had a stronger effect on attractiveness in taller men than in shorter men. There was a similar increase in the positive effect of penis size on attractiveness with a more masculine body shape (i.e., greater shoulder-to-hip ratio). Surprisingly, larger penis size and greater height had almost equivalent positive effects on male attractiveness. Our results support the hypothesis that female mate choice could have driven the evolution of larger penises in humans. More broadly, our results show that precopulatory sexual selection can play a role in the evolution of genital traits.
Publisher: Elsevier BV
Date: 07-2007
DOI: 10.1086/518695
Publisher: The Royal Society
Date: 15-09-2009
Abstract: Sexual selection is a major force behind the rapid evolution of male genital morphology among species. Most within-species studies have focused on sexual selection on male genital traits owing to events during or after copulation that increase a male's share of paternity. Very little attention has been given to whether genitalia are visual signals that cause males to vary in their attractiveness to females and are therefore under pre-copulatory sexual selection. Here we show that, on average, female eastern mosquitofish Gambusia holbrooki spent more time in association with males who received only a slight reduction in the length of the intromittent organ (‘gonopodium’) than males that received a greater reduction. This preference was, however, only expressed when females chose between two large males for small males, there was no effect of genital size on female association time.
Publisher: Wiley
Date: 26-08-2019
Abstract: Few studies have simultaneously compared ageing within genetically similar populations in both laboratory and natural environments. Such comparisons are important for interpreting laboratory studies, because factors such as diet could affect ageing in environment-dependent ways. Using a natural population of antler flies (Protopiophila litigata), we conducted separate factorial experiments in 2012 and 2013 that compared age-specific male survival and mating success in laboratory cages versus a natural field environment while supplementing their diets with protein or sugar. We found consistent and substantial increases in both survival and mating rates in the laboratory compared to the field, but remarkably, despite these large differences actuarial ageing was only higher in the laboratory than in the field in 2012 and similar in the two environments in 2013. In both years, there was no difference between environments in reproductive ageing. We found that males fed protein had a higher mortality rate than males fed sugar (strong and low support in 2012 and 2013, respectively). In contrast, diet did not strongly impact average mating rates, actuarial ageing or reproductive ageing in either experiment. Our results provide the first evidence that the negative effect of protein on life span reported in many laboratory studies can also occur in wild populations, although perhaps less consistently. They also highlight how laboratory environments can influence life-history traits and suggest caution when extrapolating from the laboratory to the field.
Publisher: Springer Science and Business Media LLC
Date: 13-03-2008
Publisher: Springer Science and Business Media LLC
Date: 21-12-2018
Publisher: Springer International Publishing
Date: 2016
Publisher: The Royal Society
Date: 14-06-2017
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 in idual 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.
Publisher: Wiley
Date: 04-02-2013
DOI: 10.1111/BRV.12022
Abstract: There are two reasons why researchers are interested in the phenotypic relationship between the expression of male secondary sexual characters (SSCs) and 'ejaculate quality' (defined as sperm/ejaculate traits that are widely assumed to increase female fertility and/or sperm competitiveness). First, if the relationship is positive then females could gain a direct benefit by choosing more attractive males for fertility assurance reasons ('the phenotype-linked fertility' hypothesis). Second, there is much interest in the direction of the correlation between traits favoured by pre-copulatory sexual selection (i.e. affecting mating success) and those favoured by post-copulatory sexual selection (i.e. increasing sperm competitiveness). If the relationship is negative this could lead to the two forms of selection counteracting each other. Theory predicts that the direction of the relationship could be either positive or negative depending on the underlying genetic variance and covariance in each trait, the extent of variation among males in condition (resources available to allocate to reproductive traits), and variation among males in the cost or rate of mating. We conducted a meta-analysis to determine the average relationship between the expression of behavioural and morphological male secondary sexual characters and four assays of ejaculate quality (sperm number, viability, swimming speed and size). Regardless of how the data were partitioned the mean relationship was consistently positive, but always statistically non-significant. The only exception was that secondary sexual character expression was weakly but significantly positively correlated with sperm viability (r = 0.07, P < 0.05). There was no significant difference in the strength or direction of the relationship between behavioural and morphological SSCs, nor among relationships using the four ejaculate quality assays. The implications of our findings are discussed.
Publisher: Wiley
Date: 09-2008
DOI: 10.1111/J.1420-9101.2008.01560.X
Abstract: Female crickets can exert post-copulatory mating preferences by prematurely removing a male's spermatophore after copulation, which terminates sperm transfer. Although most models of sexual selection assume that female mating preferences are heritable, there has been little work addressing genetic variation underlying post-copulatory mate choice. We used a paternal half-sib design, in which different males were randomly assigned as mates to several females to create half-sib families, to determine the heritability of spermatophore retention time in female house crickets, Acheta domesticus. There was significant additive genetic variance in the timing of spermatophore removal by females [h(2) = 0.50 +/- 0.19 (+/- SE)], suggesting that the timing of spermatophore removal is determined, in part, by the female's own genotype independent of the quality of her mate. The relatively high heritability of spermatophore retention time may be reflective of the absence of strong selection on this trait, consistent with previous work showing no difference in the fitness of females permitted to freely remove the spermatophore of their mates and those forced to accept complete ejaculates.
Publisher: Wiley
Date: 25-09-2015
DOI: 10.1111/BRV.12220
Abstract: Females can benefit from mate choice for male traits (e.g. sexual ornaments or body condition) that reliably signal the effect that mating will have on mean offspring fitness. These male-derived benefits can be due to material and/or genetic effects. The latter include an increase in the attractiveness, hence likely mating success, of sons. Females can potentially enhance any sex-biased benefits of mating with certain males by adjusting the offspring sex ratio depending on their mate's phenotype. One hypothesis is that females should produce mainly sons when mating with more attractive or higher quality males. Here we perform a meta-analysis of the empirical literature that has accumulated to test this hypothesis. The mean effect size was small (r = 0.064-0.095 i.e. explaining <1% of variation in offspring sex ratios) but statistically significant in the predicted direction. It was, however, not robust to correction for an apparent publication bias towards significantly positive results. We also examined the strength of the relationship using different indices of male attractiveness/quality that have been invoked by researchers (ornaments, behavioural displays, female preference scores, body condition, male age, body size, and whether a male is a within-pair or extra-pair mate). Only ornamentation and body size significantly predicted the proportion of sons produced. We obtained similar results regardless of whether we ran a standard random-effects meta-analysis, or a multi-level, Bayesian model that included a correction for phylogenetic non-independence. A moderate proportion of the variance in effect sizes (51.6-56.2%) was due to variation that was not attributable to s ling error (i.e. s le size). Much of this non-s ling error variance was not attributable to phylogenetic effects or high repeatability of effect sizes among species. It was approximately equally attributable to differences (occurring for unknown reasons) in effect sizes among and within studies (25.3, 22.9% of the total variance). There were no significant effects of year of publication or two aspects of study design (experimental/observational or field/laboratory) on reported effect sizes. We discuss various practical reasons and theoretical arguments as to why small effect sizes should be expected, and why there might be relatively high variation among studies. Currently, there are no species where replicated, experimental studies show that mothers adjust the offspring sex ratio in response to a generally preferred male phenotype. Ultimately, we need more experimental studies that test directly whether females produce more sons when mated to relatively more attractive males, and that provide the requisite evidence that their sons have higher mean fitness than their daughters.
Publisher: Oxford University Press (OUP)
Date: 2011
Location: United States of America
Location: United States of America
No related grants have been discovered for Brian Mautz.