Mate choice for genetic compatibility in the house mouse

In house mice, genetic compatibility is influenced by the t haplotype, a driving selfish genetic element with a recessive lethal allele, imposing fundamental costs on mate choice decisions. Here, we evaluate the cost of genetic incompatibility and its implication for mate choice in a wild house mice population. In laboratory reared mice, we detected no fertility (number of embryos) or fecundity (ability to conceive) costs of the t, and yet we found a high cost of genetic incompatibility: heterozygote crosses produced 40% smaller birth litter sizes because of prenatal mortality. Surprisingly, transmission of t in crosses using +/t males was influenced by female genotype, consistent with postcopulatory female choice for + sperm in +/t females. Analysis of paternity patterns in a wild population of house mice showed that +/t females were more likely than +/+ females to have offspring sired by +/+ males, and unlike +/+ females, paternity of their offspring was not influenced by +/t male frequency, further supporting mate choice for genetic compatibility. As the major histocompatibility complex (MHC) is physically linked to the t, we investigated whether females could potentially use variation at the MHC to identify male genotype at the sperm or individual level. A unique MHC haplotype is linked to the t haplotype. This MHC haplotype could allow the recognition of t and enable pre‐ and postcopulatory mate choice for genetic compatibility. Alternatively, the MHC itself could be the target of mate choice for genetic compatibility. We predict that mate choice for genetic compatibility will be difficult to find in many systems, as only weak fertilization biases were found despite an exceptionally high cost of genetic incompatibility.     

Experimental evidence for adaptive personalities in a wild passerine bird

Individuals of the same species differ consistently in risky actions. Such ‘animal personality’ variation is intriguing because behavioural flexibility is often assumed to be the norm. Recent theory predicts that between-individual differences in propensity to take risks should evolve if individuals differ in future fitness expectations: individuals with high long-term fitness expectations (i.e. that have much to lose) should behave consistently more cautious than individuals with lower expectations. Consequently, any manipulation of future fitness expectations should result in within-individual changes in risky behaviour in the direction predicted by this adaptive theory. We tested this prediction and confirmed experimentally that individuals indeed adjust their ‘exploration behaviour’, a proxy for risk-taking behaviour, to their future fitness expectations. We show for wild great tits (Parus major) that individuals with experimentally decreased survival probability become faster explorers (i.e. increase risk-taking behaviour) compared to individuals with increased survival probability. We also show, using quantitative genetics approaches, that non-genetic effects (i.e. permanent environment effects) underpin adaptive personality variation in this species. This study thereby confirms a key prediction of adaptive personality theory based on life-history trade-offs, and implies that selection may indeed favour the evolution of personalities in situations where individuals differ in future fitness expectations.     

Personality‐Dependent Survival in the Marine Isopod Idotea balthica

We studied the fitness effects of animal personality by measuring activity and its relation to survival in the marine isopod Idotea balthica. We asked (1) whether activity could be considered to be a personality trait, (2) whether this trait is connected to survival, and (3) whether personality and survival exhibit sex differences. We found that activity fulfilled the criteria of personality as individuals had consistent between‐individual differences over time and across situations. Consistent individual differences in activity were associated with fitness as the survival probability of active individuals was lower, but this did not depend on sex. Our results demonstrate that personality exists in I. balthica and support recent suggestions that the association between personality and life‐history traits is a central component in mediating animal personality.     

Female house mice avoid fertilization by t haplotype incompatible males in a mate choice experiment

The t haplotype in house mice is a well‐known selfish genetic element with detrimental, nonadditive fitness consequences to its carriers: recessive lethal mutations cause t/t homozygotes to perish in utero. Given the severe genetic incompatibility imposed by the t haplotype, we predict females to avoid fertilization by t haplotype incompatible males. Indeed, some of the strongest evidence for compatibility mate choice is related to the t haplotype in house mice. However, all previous evidence for compatibility mate choice in this system is based on olfactory preference. It is so far unknown how general these preferences are and whether they are relevant in an actual mating context. Here, we assess female compatibility mate choice related to t haplotypes in a setting that – for the first time – allowed females to directly interact and mate with males. This approach enabled us to analyse female behaviour during the testing period, and the resulting paternity success and fitness consequences of a given choice. We show that genetic incompatibilities arising from the t haplotype had severe indirect fitness consequences and t females avoided fertilization by t incompatible males. The results are inconclusive whether this avoidance of t fertilization by t females was caused by pre‐ or post‐copulatory processes.     

Evolutionary quantitative genetics of behavioral responses to handling in a wild passerine

Behavioral differences between individuals that are consistent over time characterize animal personality. The existence of such consistency contrasts to the expectation based on classical behavioral theory that facultative behavior maximizes individual fitness. Here, we study two personality traits (aggression and breath rate during handling) in a wild population of blue tits during 2007–2012. Handling aggression and breath rate were moderately heritable (h² = 0.35 and 0.20, respectively) and not genetically correlated (r_A = 0.06) in adult blue tits, which permits them to evolve independently. Reciprocal cross‐fostering (2007–2010) showed that offspring reared by more aggressive males have a higher probability to recruit. In addition, offspring reared by pairs mated assortatively for handling aggression had a higher recruitment probability, which is the first evidence that both parents' personalities influence their reproductive success in the wild in a manner independent of their genetic effects. Handling aggression was not subjected to survival selection in either sex, but slow‐breathing females had a higher annual probability of survival as revealed by capture–mark–recapture analysis. We find no evidence for temporal fluctuations in selection, and thus conclude that directional selection (via different fitness components) acts on these two heritable personality traits. Our findings show that blue tit personality has predictable fitness consequences, but that facultative adjustment of an individual's personality to match the fitness maximum is likely constrained by the genetic architecture of personality. In the face of directional selection, the presence of heritable variation in personality suggests the existence of a trade‐off that we have not identified yet.     

Genetic Basis of Mating Preferences in Wild House Mice

This paper reviews work conducted over the last several yearson the effect of genetic differences within the t-complex ofwild house mice on female mating preference. Wild mice are polymorphicfor a mutation within the t complex on chromosome 17. About25% of wild mice are heterozygous (+/t) for a t-haplotype andthe remainder are +/+. These t-haplotypes have a number of deleteriouseffects when homozygous and hence t/t individuals are rarelyfound in wild populations. We have examined preferences of +/+and +/t females for males of both genotypes. We have found that+/t, but not +/+ females have strong preferences for +/+ males.These preferences can be modified by a variety of factors includingestrous condition of the female (the preferences are strongeramong estrous than diestrous females) and the dominance statusof the male (when forced to choose, females give priority tomale dominance status over t complex genotype in choosing males).The restiction of preference to +/t females indicates that geneson t haplotypes modulate these preferences. Because t haplotypesinclude the major histocompatibility complex (MHC) of the mousewe designed a study to ascertain whether the preferences of+/t females were associated with the MHC. Results of the studyindicate that the preferences are independent of the MHC. Furtherwork testing females carrying a partial t-haplotype (t^w18) indicatesthat the genes for mating preference are localized in the regionof the t complex distal to the MHC. A large number of t haplotypesare found in wild mouse populations. Females that are themselves+/t when forced to choose between 2 +/t males (one carryinga haplotype that is the same as their own and one carrying ahaplotype that is different) prefer males carrying t-haplotypesthat differ from their own. Finally, we conclude that matingpreference may only be a weak force regulating the frequencyof t-mutations in wild mouse populations. The impact of matingpreference on population genetics of genes within this regionis muted because of the great importance of male dominance rankin determining mating patterns within interacting social groups.     

Resource availability modulates the effect of body size on reproductive development

Within-species variation in animal body size predicts major differences in life history, for example, in reproductive development, fecundity, and even longevity. Purely from an energetic perspective, large size could entail larger energy reserves, fuelling different life functions, such as reproduction and survival (the “energy reserve” hypothesis). Conversely, larger body size could demand more energy for maintenance, and larger individuals might do worse in reproduction and survival under resource shortage (the “energy demand” hypothesis). Disentangling these alternative hypotheses is difficult because large size often correlates with better resource availability during growth, which could mask direct effects of body size on fitness traits. Here, we used experimental body size manipulation in the freshwater cnidarian Hydra oligactis, coupled with manipulation of resource (food) availability to separate direct effects of body size from resource availability on fitness traits (sexual development time, fecundity, and survival). We found significant interaction between body size and food availability in sexual development time in both males and females, such that large individuals responded less strongly to variation in resource availability. These results are consistent with an energy reserve effect of large size in Hydra. Surprisingly, the response was different in males and females: small and starved females delayed their reproduction, while small and starved males developed reproductive organs faster. In case of fecundity and survival, both size and food availability had significant effects, but we detected no interaction between them. Our observations suggest that in Hydra, small individuals are sensitive to fluctuations in resource availability, but these small individuals are able to adjust their reproductive development to maintain fitness.     

Exploration Behavior and Morphology are Correlated in Captive Gray Mouse Lemurs (<Emphasis Type="Italic">Microcebus murinus</Emphasis>)

Behavior varies among individuals and is flexible within individuals. However, studies of behavioral syndromes and animal personality have demonstrated that animals can show consistency in their behavior and as such may be restricted in their behavioral responses. Like any other trait, including morphology, performance, or physiology, personality is now considered an important component of ecology and may have fitness consequences. Moreover, in some species personality correlates with other traits, as predicted in the context of a recent theoretical framework postulating that individual differences in growth and body size can affect behavior through effects on growth–mortality tradeoffs. This “pace of life” hypothesis predicts that animals that explore more should be larger and have higher growth rates than those that explore less. We tested for associations between morphology and a behavioral trait in a captive colony of gray mouse lemurs (Microcebus murinus). We used open-field tests to evaluate exploration behavior and measured a series of morphological traits in 72 individuals (32 males and 40 females). Our results show that the latency to start exploring correlates positively with adult body size and body weight at birth. These data provide evidence for a link between morphology and behavior in this species, thus supporting predictions of dispersal models but diverging from the predictions of the “pace of life” model.     

Personality, habitat use, and their consequences for survival in North American red squirrels Tamiasciurus hudsonicus

Personality affects many aspects of an individual's behaviour, life history and fitness, and has been shown to be moderately heritable in wild populations. Correlations between personality and risk‐taking that lead to life history tradeoffs could act to maintain variation in personality within a population, but this has not yet been tested. In this study, we used females from a marked population of North American red squirrels in Kluane, Yukon, to determine whether personality predicts risk‐taking in the wild, and whether these risk‐taking behaviours result in life history tradeoffs. We measured personality in open field and mirror image stimulation tests and extracted two traits, activity and aggressiveness, using principal component analysis and mixed model techniques. Using trapping records for individuals from February to September 2005, we obtained three measures of risk‐taking: the number of trapping events, the number of different trapping locations, and the maximum distance between the home territory and a trapping event. We used GLMs to determine whether the activity and aggressiveness of individuals are related to these risk‐taking behaviours, and found that active squirrels were trapped significantly more frequently and at a greater number of locations. There was also a significant interaction between activity and aggressiveness to affect the maximum capture distance. To determine if there are fitness tradeoffs associated with these risk‐taking behaviours, we examined female bequeathal behaviour and survival. Bequeathing a territory increases offspring probability of overwinter survival, and we found that an increasing number of trapping locations was associated with an increasing tendency to bequeath. Active females were less likely to survive until the following spring. Risk‐taking is therefore predicted by personality in this population, and they affect both survival and territorial bequeathal. These fitness tradeoffs may therefore lead to the maintenance of variation in personality.     

Detrimental effects of an autosomal selfish genetic element on sperm competitiveness in house mice

Female multiple mating (polyandry) is widespread across many animal taxa and indirect genetic benefits are a major evolutionary force favouring polyandry. An incentive for polyandry arises when multiple mating leads to sperm competition that disadvantages sperm from genetically inferior mates. A reduction in genetic quality is associated with costly selfish genetic elements (SGEs), and studies in invertebrates have shown that males bearing sex ratio distorting SGEs are worse sperm competitors than wild-type males. We used a vertebrate model species to test whether females can avoid an autosomal SGE, the t haplotype, through polyandry. The t haplotype in house mice exhibits strong drive in t heterozygous males by affecting spermatogenesis and is associated with homozygous in utero lethality. We used controlled matings to test the effect of the t haplotype on sperm competitiveness. Regardless of mating order, t heterozygous males sired only 11% of zygotes when competing against wild-type males, suggesting a very strong effect of the t haplotype on sperm quality. We provide, to our knowledge, the first substantial evidence that polyandry ameliorates the harmful effects of an autosomal SGE arising through genetic incompatibility. We discuss potential mechanisms in our study species and the broader implications for the benefits of polyandry.     

Social personality trait and fitness

Several recent studies have explored various aspects of animal personality and their ecological consequences. However, the processes responsible for the maintenance of personality variability within a population are still largely unknown. We have recently demonstrated that social personality traits exist in the common lizard (Lacerta vivipara) and that the variation in sociability provides an explanation for variable dispersal responses within a given species. However, we need to know the fitness consequences of variation in sociability across environmental contexts in order to better understand the maintenance of such variation. In order to achieve this, we investigated the relationship between sociability and survival, body growth and fecundity, in one-year-old individuals in semi-natural populations with varying density. 'Asocial' and 'social' lizards displayed different fitness outcomes in populations of different densities. Asocial lizards survived better in low-density populations, while social females reproduced better. Spatiotemporal variation in environmental conditions might thus be the process underlying the maintenance of these personality traits within a population. Finally, we also discuss the position of sociability in a more general individual behavioural pattern including boldness, exploration and aggressiveness.     

Reproductive competition promotes the evolution of female weaponry

Secondary sexual traits in females are a relatively rare phenomenon. Empirical studies have focused on the role of male mate choice in their evolution; however, recently it has been suggested that secondary sexual traits in females are more likely to be under selection via reproductive competition. We investigated female competition and the influence of female phenotype on fitness in Onthophagus sagittarius, a species of dung beetle that exhibits female-specific horns. We compared reproductive fitness when females were breeding in competition versus breeding alone and found that competition for breeding resources reduced fitness for all females, but that smaller individuals suffered a greater fitness reduction than larger individuals. When females were matched for body size, those with the longest horns gained higher reproductive fitness. The fitness function was positive and linear, favouring increased horn expression. Thus, we present evidence that female body size and horn size in O. sagittarius are under directional selection via competition for reproductive resources. Our study is a rare example of female contest competition selecting for female weaponry.     

Are shy individuals less behaviorally variable? Insights from a captive population of mouse lemurs

Increasingly, individual variation in personality has become a focus of behavioral research in animal systems. Boldness and shyness, often quantified as the tendency to explore novel situations, are seen as personality traits important to the fitness landscape of individuals. Here we tested for individual differences within and across contexts in behavioral responses of captive mouse lemurs (Microcebus murinus) to novel objects, novel foods, and handling. We report consistent differences in behavioral responses for objects and handling. We also found that the responses to handling and novel objects were correlated and repeatable. Lastly, we show that shyer individuals may show less variability in their behavioral responses. This study provides new information on the potential for behavioral syndromes in this species and highlights differences in the degree to which behavioral types (e.g., shy/bold) vary in their behavioral responses.     

Shy birds play it safe: personality in captivity predicts risk responsiveness during reproduction in the wild

Despite a growing body of evidence linking personality to life-history variation and fitness, the behavioural mechanisms underlying these relationships remain poorly understood. One mechanism thought to play a key role is how individuals respond to risk. Relatively reactive and proactive (or shy and bold) personality types are expected to differ in how they manage the inherent trade-off between productivity and survival, with bold individuals being more risk-prone with lower survival probability, and shy individuals adopting a more risk-averse strategy. In the great tit (Parus major), the shy–bold personality axis has been well characterized in captivity and linked to fitness. Here, we tested whether ‘exploration behaviour’, a captive assay of the shy–bold axis, can predict risk responsiveness during reproduction in wild great tits. Relatively slow-exploring (shy) females took longer than fast-exploring (bold) birds to resume incubation after a novel object, representing an unknown threat, was attached to their nest-box, with some shy individuals not returning within the 40 min trial period. Risk responsiveness was consistent within individuals over days. These findings provide rare, field-based experimental evidence that shy individuals prioritize survival over reproductive investment, supporting the hypothesis that personality reflects life-history variation through links with risk responsiveness.     

圈养马麝(Moschus sifanicus)个性特征及与麝香分泌的关系

采用焦点取样和扫描取样方法,对甘肃兴隆山麝场圈养马麝(Moschus sifanicus)交配季节及非交配季节进行行为取样。通过行为样本,对个体个性特征(活跃性、领域性、刻板性、探索性、行为冗余性)进行标准化处理,分析了年龄及性别对个性特征的效应,以及交配季节与非交配季节之间个性特征的差异,同时分析了马麝个性特征与泌香量的相互关系。结果表明:年龄增加对活跃性具有降低的效应(P0.05),并对非交配季节领域性具有降低效应(P0.05);非交配季节里雌性活跃性高于雄性(P0.05);不同季节间个性特征存在差异,交配季节活跃性与领域性均有高于非交配季节的趋势,并且活跃性与领域性在两季节间呈正相关关系(P0.05);雄麝泌香量与活跃性存在正相关关系(交配季节:r=0.518,P0.05;非交配季节:r=0.397,P0.05),与交配季节领域性同样具有正相关关系(r=0.406,P0.05)。本研究通过行为取样方法首次对马麝个性特征进行定量分析,探讨了将个性特征,特别是活跃性和领域性,作为泌香量预测指标的方法,对圈养动物个性研究的理论创新具有指导作用,同时对麝香及麝类资源的发展具有实践意义。     

Ectoparasites and fitness of female Columbian ground squirrels

Parasites play an important role in the evolution of host traits via natural selection, coevolution and sexually selected ornaments used in mate choice. These evolutionary scenarios assume fitness costs for hosts. To test this assumption, we conducted an ectoparasite removal experiment in free-living Columbian ground squirrels (Urocittelus columbianus) in four populations over three years. Adult females were randomly chosen to be either experimentally treated with anti-parasite treatments (spot-on solution and flea powder, N = 61) or a sham treatment (control, N = 44). We expected that experimental females would show better body condition, increased reproductive success and enhanced survival. Contrary to our expectations, body mass was not significantly different between treatments at mating, birth of litter or weaning of young. Further, neither number nor size of young at weaning differed significantly between the two treatments. Survival to the next spring for adult females and juveniles was not significantly different between experimental and control treatments. Finally, annual fitness was not affected by the treatments. We concluded that females and their offspring were able compensate for the presence of ectoparasites, suggesting little or no fitness costs of parasites for females in the different colonies and during the years of our experiments.     

An experimental approach to the formation of diet preferences and individual specialisation in European mink

Individual dietary specialisation can occur within populations even when average diets suggest that the population has a generalist feeding strategy. Individual specialisation may impact fitness and has been related to demographic traits, ecological opportunity, competition, learning and animal personality. However, the causation and formation of individual specialisation are not fully understood. Experiments on animals raised in controlled environments provide an opportunity to examine dietary preferences and learning largely independent from variation in lifetime experiences and ecological opportunity. Here, we use a feeding experiment to examine individual specialisation and learning in captive bred European mink (Mustela lutreola) in an Estonian conservation programme. In a series of cafeteria experiments, animals could choose between one familiar food item (Baltic herring Clupea harengus membras) and two initially novel ones (noble crayfish Astacus astacus and house mouse Mus musculus). In general, mice were rarely eaten whilst crayfish consumption increased over time and fish decreased. At the individual level, there was a mix of generalists and crayfish or fish specialists, and the individuals differed in learning time in relation to novel prey. Our results indicate that individual variation in innate preferences and learning both contributes to individual diet specialisation. The differences in learning indicate individual variation in behavioural plasticity, which in turn can be related to personality. This could be of concern in conservation, as personality has been shown to affect survival in translocations.     

Blood cortisol concentrations predict boldness in juvenile mulloway (Argyosomus japonicus)

There is a growing interest in animal personality because individual variation is the substrate of the evolutionary process. Despite revelations that personality traits affect key fitness variables, little is known about the proximate mechanisms generating consistent behavioural differences between individuals. Boldness, the propensity to take risks, is one of the most widely studied aspects of personality in fishes. We assessed the position of juvenile Argyosomus japonicus on the ??boldness?Cshyness?? continuum by repeatedly recording the time taken to exit a refuge and explore a novel environment. Stress-related hormone concentrations after exposure to a mild stressor were analysed 1?month before behavioural assays and found to be significantly linked to boldness scores. Shy fish had significantly higher plasma cortisol concentrations in response to handling stress than bold fish. Spontaneous switching between personality categories occurred between trials, highlighting the importance of repeated testing of personality traits over time to correctly attribute personality.     

Polyandry and the decrease of a selfish genetic element in a wild house mouse population

Despite deleterious effects on individuals, the t haplotype is a selfish genetic element present in many house mouse populations. By distorting the transmission ratio, +/t males transmit the t haplotype to up to 90% of their offspring. However, t/t individuals perish in utero. Theoretical models based on these properties predict a much higher t frequency than observed, leading to the t paradox. Here, we use empirical field data and theoretical approaches to investigate whether polyandry is a female counterstrategy against the negative fitness consequences of such distorters. We found a significant decrease of the t frequency over a period of 5.5 years that cannot be explained by the effect of transmission ratio distortion and recessive lethals, despite significantly higher life expectancy of +/t females compared to +/+ females. We quantified life-history data and homozygous and heterozygous fitness effects. Population subdivision and inbreeding were excluded as evolutionary forces influencing the t system. The possible influence of polyandry on the t system was then investigated by applying a stochastic model to this situation. Simulations show that polyandry can explain the observed t dynamics, making it a biologically plausible explanation for low t frequencies in natural populations in general.     

You eat what you are: personality‐dependent filial cannibalism in a fish with paternal care

Many animal parents invest heavily to ensure offspring survival, yet some eventually consume some or all of their very own young. This so‐called filial cannibalism is known from a wide range of taxa, but its adaptive benefit remains largely unclear. The extent to which parents cannibalize their broods varies substantially not only between species, but also between individuals, indicating that intrinsic behavioral differences, or animal personalities, might constitute a relevant proximate trigger for filial cannibalism. Using a marine fish with extensive paternal care, the common goby (Pomatoschistus microps), we investigated the influence of animal personality on filial cannibalism by assessing (1) behavioral consistency across a breeding and a nonbreeding context; (2) correlations between different breeding (egg fanning; filial cannibalism) and nonbreeding (activity) behaviors, and, in a separate experiment; (3) whether previously established personality scores affect filial cannibalism levels. We found consistent individual differences in activity across contexts. Partial filial cannibalism was independent of egg fanning but correlated strongly with activity, where active males cannibalized more eggs than less active males. This pattern was strong initially but vanished as the breeding season progressed. The incidence of whole clutch filial cannibalism increased with activity and clutch size. Our findings indicate that filial cannibalism cannot generally be adjusted independently of male personality and is thus phenotypically less plastic than typically assumed. The present work stresses the multidimensional interaction between animal personality, individual plasticity and the environment in shaping filial cannibalism.