Sexual dimorphism in trait variability and its eco-evolutionary and statistical implications

Biomedical and clinical sciences are experiencing a renewed interest in the fact that males and females differ in many anatomic, physiological, and behavioural traits. Sex differences in trait variability, however, are yet to receive similar recognition. In medical science, mammalian females are assumed to have higher trait variability due to estrous cycles (the ‘estrus-mediated variability hypothesis’); historically in biomedical research, females have been excluded for this reason. Contrastingly, evolutionary theory and associated data support the ‘greater male variability hypothesis’. Here, we test these competing hypotheses in 218 traits measured in >26,900 mice, using meta-analysis methods. Neither hypothesis could universally explain patterns in trait variability. Sex bias in variability was trait-dependent. While greater male variability was found in morphological traits, females were much more variable in immunological traits. Sex-specific variability has eco-evolutionary ramifications, including sex-dependent responses to climate change, as well as statistical implications including power analysis considering sex difference in variance.SRKZ and ML were supported by the Australian (ARC) Discovery Grant (DP180100818) awarded to SN. JM was supported by EMBL core funding and the NIH Common Fund (UM1-H G006370). AMS was supported by an ARC fellowship (DE180101520)

Transgenerational effects of maternal sexual interactions in seed beetles

Mating often bears large costs to females, especially in species with high levels of sexual conflict over mating rates. Given the direct costs to females associated with multiple mating, which include reductions in lifespan and lifetime reproductive success, past research focused on identifying potential indirect benefits (through increases in offspring fitness) that females may accrue. Far less attention has, however, been devoted to understanding how costs of sexual interactions to females may extend across generations. Hence, little is known about the transgenerational implications of variation in mating rates, or the net consequences of maternal sexual activities across generations. Using the seed beetle, Callosobruchus maculatus, a model system for the study of sexual conflict, we investigate the effects of mating with multiple males versus a single male, and tease apart effects due to sexual harassment and those due to mating per se, over three generations. A multigenerational analysis indicated that females that were exposed to ongoing sexual harassment and who also were permitted to mate with multiple males showed no difference in net fitness compared to females that mated just once without ongoing harassment. Intriguingly, however, females that were continually harassed, but permitted to mate just once, suffered a severe decline in net fitness compared to females that were singly (not harassed) or multiply mated (harassed, but potentially gaining benefits via mating with multiple males). Overall, the enhanced fitness in multiply mated compared to harassed females may indicate that multiple mating confers transgenerational benefits. These benefits may counteract, but do not exceed (i.e., we found no difference between singly and multiply mated females), the large transgenerational costs of harassment. Our study highlights the importance of examining transgenerational effects from an inclusive (looking at both indirect benefits but also costs) perspective, and the need to investigate transgenerational effects across several generations if we are to fully understand the consequences of sexual interactions, sexual conflict evolution, and the interplay of sexual conflict and multi-generational costs and benefits

The importance of habitat resistance for movement decisions in the common lizard, Lacerta vivipara

Background: Movement behaviour can be influenced by a multitude of biotic and abiotic factors. Here, we investigate the speed of movement in relation to environmental and individual phenotypic properties in subadult common lizards (Lacerta vivipara). We aim to disentangle the importance of substrate, cover, humidity, basking opportunity and individual phenotype on moving tendencies in 12 treatment combinations, at which each lizard was tested.Results: We find that movement behaviour depends on the starting conditions, the physical properties of the dispersal corridor, and on the individuals' phenotype. Specifically, the presence of cover and substrate providing suitable traction in the corridor had positive effects on individual movement decisions. Additionally, we find high phenotypic variation in the propensity to move dependent on the presence of cover. Individual back patterns also strongly affected movement decisions in interaction with the physical properties of the dispersal corridor.Conclusions: Our results highlight the importance of understanding the habitat resistance for movement patterns, with humid habitats with covering vegetation providing the best conditions to initiate movement in the common lizard. In addition, population effects, differences in back pattern phenotype and individual plasticity were identified as key parameters influencing movement behaviour

2009a. Sexual dimorphism in life history: age, survival, c© 2012 The Authors. Published by Blackwell Publishing

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. ABSTRACT: Males and females differ in their reproductive strategies. Accordingly, sexually dimorphic optima in the allocation of resources to reproduction should select for sex-specific life histories, including sex-specific resolution of the key trade-off between reproduction and longevity. While males are expected to increase reproductive effort with increasing age under sexual selection theory, female reproductive effort should rather decrease after maturity, due to waning selection pressure at older ages. Sex differences in reproductive trade-offs and in the external mortality hazards experienced during the population's evolutionary history are both likely to shape sex differences in re productive and actuarial (age-specific mortality) aging. Despite the importance of small-bodied, short-lived animals as laboratory mod els for life-history and aging studies, very little is known about sex differences in life-history patterns under natural conditions. Here, we tested for sex-specific patterns of reproductive and actuarial aging in field crickets under near-natural conditions. Both males and fe males showed actuarial senescence, with females exhibiting more rapid aging than males but with a later onset. Female and male reproductive effort showed a senescent decrease, with the peaks at different ages. Our findings provide the first demonstration of sexual dimorphism in age-dependent patterns of both survival and repro duction in an insect under near-natural conditions. The University of Chicago Press an

Data from: Short term variation in sperm competition causes sperm mediated epigenetic effects on early offspring performance in the zebrafish

The inheritance of non-genetic factors is increasingly seen to play a major role in ecology and evolution. While the causes and consequences of epigenetic effects transmitted from the mother to the offspring have received ample attention, much less is known about how variation in the condition of the father affects the offspring. Here, we manipulated the intensity of sperm competition experienced by male zebrafish Danio rerio to investigate the potential for sperm-mediated epigenetic effects over a relatively short period of time. We found that the rapid responses of males to varying intensity of sperm competition not only affected sperm traits as shown previously, but also the performance of the resulting offspring. We observed that males exposed to high intensity of sperm competition produced faster swimming and more motile sperm, and sired offspring that hatched over a narrower time frame but exhibited a lower survival rate than males exposed to low intensity of sperm competition. Our results provide striking evidence for short-term paternal effects and the possible fitness consequences of such sperm-mediated non-genetic factors not only for the resulting offspring but also for the female

The effect of coloration and temperature on sprint performance in male and female wall lizards

Phenotypic coloration in animals is often expected to have a signalling function, but it may also evolve as a correlated trait that reflects life-history strategy, social strategy, or ecological divergence. Wall lizards (Podarcis muralis) exhibit substantial colour variation, with both males and females being red, white, yellow, or a mixture of these colours. However, the biological significance of these colour morphs remains unknown. Here we investigate the relationship between coloration and temperature-dependent locomotor performance in an attempt to identify the adaptive significance of colour variation in this species. We investigate the maximum sprint speed of males and females of each of these colour morphs across seven different temperatures, using general additive mixed models (GAMMs). We predicted that the different sexes and colour phenotypes would exhibit differences in sprint speed performance, potentially indicating a correlation between coloration and adaptation into different ecological niches. We found no difference in performance of the discrete colour morphs, but amongst individuals that exhibited red coloration, those with a greater percentage of red were slower than those with less red coloration. This suggests a trade-off between red coloration and high sprint performance in this species. Furthermore, larger animals performed better, independent of colour and sex. Finally, we found no relative or absolute difference between males and females in their sprint performance. Taken together, our results suggest that there is no sex-specific or colou

Hatching

Numbers of offspring hatched / unhatched within any given clutch, measured in 2 hr time intervalsfrom 48 hours post fertilisation until 80 hours post fertilisation (or less, if all offspring had hatched prior to this point in time). File also contains information in MaleID, FemaleID, Treatment and experimental Block

LarvalSurvival

Survival at 4 points (from 3h post fertilisation to 1 week of age). Reported are numbers of offspring alive / dead for each clutch

SpermVelocity

Sperm swimming speed parameters recorded (VCL, VAP, VSL) at 4 time points (10 / 20/30/40 seconds post activation)