Early social complexity influences social behaviour but not social trajectories in a cooperatively breeding cichlid fish

Social competence-defined as the ability to optimize social behaviour according to available social information-can be influenced by the social environment experienced in early life. In cooperatively breeding vertebrates, the current group size influences behavioural phenotypes, but it is not known whether the group size experienced in early life influences behavioural phenotypes generally or social competence specifically. We tested whether being reared in large versus small groups for the first two months of life affects social behaviours, and associated life-history traits, in the cooperatively breeding cichlid Neolamprologus pulcher between the ages of four and twelve months. As we predicted, fish raised in larger and more complex groups showed higher social competence later in life. This was shown in several ways: they exhibited more, and earlier, submissive behaviour in response to aggression from a dominant conspecific, and-in comparison to fish raised in small groups-they exhibited more flexibility in the expression of submissive behaviour. By contrast, there was no evidence that early social complexity, as captured by the group size, affects aggression or exploration behaviour nor did it influence the propensity to disperse or show helping behaviour. Our results emphasize the importance of early-life social complexity for the development of social competence.

Misalignment of plastic and evolutionary responses of lifespan to novel carbohydrate diets

Diet elicits varied effects on longevity across a wide range of animal species where dietary discordance between an organisms' evolutionary and developmental dietary history is increasingly recognized to play a critical role in shaping lifespan. However, whether such changes, predominantly assessed in a single generation, lead to evolutionary shifts in lifespan remains unclear. In this study, we used an experimental evolution approach to test whether changes in an organisms' evolutionary and developmental dietary history, specifically carbohydrate content, causes lifespan evolution in Drosophila serrata. After 30 generations, we investigated the evolutionary potential of lifespan in response to four novel diets that varied systematically in their ratio of carbohydrate-protein content. We also examined developmental plasticity effects using a set of control populations that were raised on the four novel environments allowing us to assess the extent to which plastic responses of lifespan mirrored adaptive responses observed following experimental evolution. Both high- and low-carbohydrate diets elicited plastic effects on lifespan; however, the plastic responses for lifespan to developmental diets bore little resemblance to the evolved responses on evolutionary diets. Understanding the dietary conditions regulating the match/mismatch of plastic and evolved responses will be important in determining whether a particular match/mismatch combination is adaptive for lifespan. While the differences in evolutionary diet by developmental diet interactions are only beginning to be elucidated, this study lays the foundation for future investigations of carbohydrate contributions to evolved and plastic effects on health and lifespan.

Genetic and context-specific effects on individual inhibitory control performance in the guppy (Poecilia reticulata)

Among-individual variation in cognitive traits, widely assumed to have evolved under adaptive processes, is increasingly being demonstrated across animal taxa. As variation among individuals is required for natural selection, characterizing individual differences and their heritability is important to understand how cognitive traits evolve. Here, we use a quantitative genetic study of wild-type guppies repeatedly exposed to a 'detour task' to test for genetic variance in the cognitive trait of inhibitory control. We also test for genotype-by-environment interactions (GxE) by testing related fish under alternative experimental treatments (transparent vs. semi-transparent barrier in the detour-task). We find among-individual variation in detour task performance, consistent with differences in inhibitory control. However, analysis of GxE reveals that heritable factors only contribute to performance variation in one treatment. This suggests that the adaptive evolutionary potential of inhibitory control (and/or other latent variables contributing to task performance) may be highly sensitive to environmental conditions. The presence of GxE also implies that the plastic response of detour task performance to treatment environment is genetically variable. Our results are consistent with a scenario where variation in individual inhibitory control stems from complex interactions between heritable and plastic components.

Mothers in a cooperatively breeding bird increase investment per offspring at the pre-natal stage when they will have more help with post-natal care

In many cooperative societies, including our own, helpers assist with the post-natal care of breeders' young and may thereby benefit the post-natal development of offspring. Here, we present evidence of a novel mechanism by which such post-natal helping could also have beneficial effects on pre-natal development: By lightening post-natal maternal workloads, helpers may allow mothers to increase their pre-natal investment per offspring. We present the findings of a decade-long study of cooperatively breeding white-browed sparrow-weaver, Plocepasser mahali, societies. Within each social group, reproduction is monopolized by a dominant breeding pair, and non-breeding helpers assist with nestling feeding. Using a within-mother reaction norm approach to formally identify maternal plasticity, we demonstrate that when mothers have more female helpers, they decrease their own post-natal investment per offspring (feed their nestlings at lower rates) but increase their pre-natal investment per offspring (lay larger eggs, which yield heavier hatchlings). That these plastic maternal responses are predicted by female helper number, and not male helper number, implicates the availability of post-natal helping per se as the likely driver (rather than correlated effects of group size), because female helpers feed nestlings at substantially higher rates than males. We term this novel maternal strategy "maternal front-loading" and hypothesize that the expected availability of post-natal help either allows or incentivizes helped mothers to focus maternal investment on the pre-natal phase, to which helpers cannot contribute directly. The potential for post-natal helping to promote pre-natal development further complicates attempts to identify and quantify the fitness consequences of helping.

Advanced Systemic Mastocytosis with associated haematological neoplasm: Treatment with avapritinib can facilitate successful bridge to allogeneic haematopoietic cell transplant

Advanced systemic mastocytosis (AdvSM) is a rare, life-limiting mast cell (MC) neoplasm, with approximately 70% patients having an associated haematological neoplasm (AHN). Avapritinib, a selective tyrosine kinase inhibitor targeting KIT D816V, has shown potent activity translating clinically into durable responses in the phase 1 EXPLORER (NCT02561988) and phase 2 PATHFINDER (NCT03580655) studies. We report three patients with AdvSM-AHN on avapritinib who achieved complete remission (CR) of SM and were successfully bridged to allogeneic haematopoietic cell transplant (allo-HCT). Two cases additionally highlight the risk of clonal evolution within the AHN component and requirement for close monitoring while on targeted therapy.

Genetic improvement of speed across distance categories in thoroughbred racehorses in Great Britain

Several studies over recent decades have reported a lack of contemporary improvement in thoroughbred racehorse speed, despite apparent additive genetic variance and putatively strong selection. More recently, it has been shown that some phenotypic improvement is ongoing, but rates are low in general and particularly so over longer distances. Here we used pedigree-based analysis of 692,534 records from 76,960 animals to determine whether these phenotypic trends are underpinned by genetic selection responses, and to evaluate the potential for more rapid improvement. We show that thoroughbred speed in Great Britain is only weakly heritable across sprint (h² = 0.124), middle-distance (h² = 0.122) and long-distance races (h² = 0.074), but that mean predicted breeding values are nonetheless increasing across cohorts born between 1995 and 2012 (and racing from 1997 to 2014). For all three race distance categories, estimated rates of genetic improvement are statistically significant and also greater than can be explained by drift. Taken together our results show genetic improvement for thoroughbred speed is ongoing but slow, likely due to a combination of long generation times and low heritabilities. Additionally, estimates of realised selection intensities raises the possibility that the contemporary selection emerging from the collective actions of horse breeders is weaker than previously assumed, particularly over long distances. We suggest that unmodelled common environment effects may have upwardly biased estimates of heritability, and thus expected selection response, previously.

Exploiting animal personality to reduce chronic stress in captive fish populations

Chronic stress is a major source of welfare problems in many captive populations, including fishes. While we have long known that chronic stress effects arise from maladaptive expression of acute stress response pathways, predicting where and when problems will arise is difficult. Here we highlight how insights from animal personality research could be useful in this regard. Since behavior is the first line of organismal defense when challenged by a stressor, assays of shy-bold type personality variation can provide information about individual stress response that is expected to predict susceptibility to chronic stress. Moreover, recent demonstrations that among-individual differences in stress-related physiology and behaviors are underpinned by genetic factors means that selection on behavioral biomarkers could offer a route to genetic improvement of welfare outcomes in captive fish stocks. Here we review the evidence in support of this proposition, identify remaining empirical gaps in our understanding, and set out appropriate criteria to guide development of biomarkers. The article is largely prospective: fundamental research into fish personality shows how behavioral biomarkers could be used to achieve welfare gains in captive fish populations. However, translating potential to actual gains will require an interdisciplinary approach that integrates the expertise and viewpoints of researchers working across animal behavior, genetics, and welfare science.

Evidence of maternal and paternal age effects on speed in thoroughbred racehorses

Effects of parental age on offspring viability have been reported in a wide range of species. However, to what extent parental age influences offspring traits beyond viability remains unclear. Moreover, previous research has primarily focused on maternal age effects. The purpose of this study was to test for paternal and maternal age effects on offspring speed in thoroughbred racehorses. We analysed over 900 000 race performances by over 100 000 horses on British racecourses between 1996 and 2019. With knowledge of the age of all 41 107 dams and 2 887 sires at offspring conception, we jointly modelled maternal and paternal age effects using a 'within-individual centring' approach. Within-parents, we identified a significant effect of maternal age on offspring speed of -0.017 yards s^-1 yr^-1 and a corresponding paternal age effect of -0.011 yards s^-1 yr^-1. Although maternal age effects were stronger (more negative), the existence and magnitude of paternal effects is particularly noteworthy, given thoroughbred sires have no involvement in parental care. Our results also suggest that the selective disappearance of both sires and dams is ongoing. These findings could potentially be used to optimize thoroughbred racehorse breeding decisions, and more generally, add to the increasing body of evidence that both maternal and paternal age affect a range of offspring characteristics.

Evidence of maternal and paternal age effects on speed in thoroughbred racehorses

Effects of parental age on offspring viability have been reported in a wide range of species. However, to what extent parental age influences offspring traits beyond viability remains unclear. Moreover, previous research has primarily focused on maternal age effects. The purpose of this study was to test for paternal and maternal age effects on offspring speed in thoroughbred racehorses. We analysed over 900 000 race performances by over 100 000 horses on British racecourses between 1996 and 2019. With knowledge of the age of all 41 107 dams and 2 887 sires at offspring conception, we jointly modelled maternal and paternal age effects using a 'within-individual centring' approach. Within-parents, we identified a significant effect of maternal age on offspring speed of -0.017 yards s^-1 yr^-1 and a corresponding paternal age effect of -0.011 yards s^-1 yr^-1. Although maternal age effects were stronger (more negative), the existence and magnitude of paternal effects is particularly noteworthy, given thoroughbred sires have no involvement in parental care. Our results also suggest that the selective disappearance of both sires and dams is ongoing. These findings could potentially be used to optimize thoroughbred racehorse breeding decisions, and more generally, add to the increasing body of evidence that both maternal and paternal age affect a range of offspring characteristics.

Evidence of maternal and paternal age effects on speed in thoroughbred racehorses

Effects of parental age on offspring viability have been reported in a wide range of species. However, to what extent parental age influences offspring traits beyond viability remains unclear. Moreover, previous research has primarily focused on maternal age effects. The purpose of this study was to test for paternal and maternal age effects on offspring speed in thoroughbred racehorses. We analysed over 900 000 race performances by over 100 000 horses on British racecourses between 1996 and 2019. With knowledge of the age of all 41 107 dams and 2 887 sires at offspring conception, we jointly modelled maternal and paternal age effects using a 'within-individual centring' approach. Within-parents, we identified a significant effect of maternal age on offspring speed of -0.017 yards s^-1 yr^-1 and a corresponding paternal age effect of -0.011 yards s^-1 yr^-1. Although maternal age effects were stronger (more negative), the existence and magnitude of paternal effects is particularly noteworthy, given thoroughbred sires have no involvement in parental care. Our results also suggest that the selective disappearance of both sires and dams is ongoing. These findings could potentially be used to optimize thoroughbred racehorse breeding decisions, and more generally, add to the increasing body of evidence that both maternal and paternal age affect a range of offspring characteristics.

Genetic and social contributions to sex differences in lifespan in Drosophila serrata

Sex differences in lifespan remain an intriguing puzzle in evolutionary biology. While explanations range from sex differences in selection to sex differences in the expression of recessive lifespan‐altering mutations (via X‐linkage), little consensus has been reached. One unresolved issue is the extent to which genetic influences on lifespan dimorphism are modulated by the environment. For example, studies have shown that sex differences in lifespan can either increase or decrease depending upon the social environment. Here, we took an experimental approach, manipulating multiple axes of the social environment across inbred long‐ and short‐lived genotypes and their reciprocal F1s in the fly Drosophila serrata. Our results reveal strong genetic effects and subtle yet significant genotype‐by‐environment interactions for male and female lifespan, specifically due to both population density and mating status. Further, our data do not support the idea that unconditional expression of deleterious X‐linked recessive alleles in heterogametic males accounts for lower male lifespan.

Differences in the temporal scale of reproductive investment across the slow-fast continuum in a passerine

Life-history strategies differ with respect to investment in current versus 'future' reproduction, but when is this future? Under the novel 'temporality in reproductive investment hypothesis', we postulate variation should exist in the time frame over which reproductive costs are paid. Slow-paced individuals should pay reproductive costs over short (e.g. inter-annual) time scales to prevent reproductive costs accumulating, whereas fast-paced individuals should allow costs to accumulate (i.e. senescence). Using Fourier transforms, we quantify adjustments in clutch size with age, across four populations of blue tits (Cyanistes caeruleus). Fast populations had more prevalent and stronger long-term changes in reproductive investment, whereas slower populations had more prevalent short-term adjustments. Inter-annual environmental variation partly accounted for short-, but not long-term changes in reproductive investment. Our study reveals individuals differ in when they pay the cost of reproduction and that failure to partition this variation across different temporal scales and environments could underestimate reproductive trade-offs.

Altruistic bet-hedging and the evolution of cooperation in a Kalahari bird

Altruism is globally associated with unpredictable environments, but we do not understand why. New theory has highlighted that unpredictable environments could favor the evolution of altruism if altruistic acts reduce environmentally induced variance in the reproductive success of relatives (“altruistic bet-hedging”). Here, we show that altruism does indeed reduce environmentally induced reproductive variance in a wild cooperative bird. Our decade-long field study reveals that altruistic helping actually has no overall effect on the mean reproductive success of relatives but instead reduces their reproductive variance. This remarkable pattern arises because helpers improve reproductive performance in dry conditions but reduce it in wet conditions. Helpers thereby specifically reduce rainfall-induced reproductive variance, the very mechanism required for altruistic bet-hedging to explain the enigmatic global association between avian altruism and unpredictable rainfall.

Sensory-based quantification of male colour patterns in Trinidadian guppies reveals no support for parallel phenotypic evolution in multivariate trait space

Parallel evolution, in which independent populations evolve along similar phenotypic trajectories, offers insights into the repeatability of adaptive evolution. Here, we revisit a classic example of parallelism, that of repeated evolution of brighter males in the Trinidadian guppy (Poecilia reticulata). In guppies, colonisation of low predation habitats is associated with emergence of 'more colourful' phenotypes since predator-induced viability selection for crypsis weakens while sexual selection by female preference for conspicuousness remains strong. Our study differs from previous investigations in three respects. First, we adopted a multivariate phenotyping approach to characterise parallelism in multitrait space. Second, we used ecologically-relevant colour traits defined by the visual systems of the two selective agents (i.e., guppy, predatory cichlid). Third, we estimated population genetic structure to test for adaptive (parallel) evolution against a model of neutral phenotypic divergence. We find strong phenotypic differentiation that is inconsistent with a neutral model but very limited support for the predicted pattern of greater conspicuousness at low predation. Effects of predation regime on each trait were in the expected direction, but weak, largely nonsignificant, and explained little among-population variation. In multitrait space, phenotypic trajectories of lineages colonising low from high predation regimes were not parallel. Our results are consistent with reduced predation risk facilitating adaptive differentiation, potentially by female choice, but suggest that this proceeds in independent directions of multitrait space across lineages. Pool-sequencing data also revealed SNPs showing greater differentiation than expected under neutrality, among which some are found in genes contributing to colour pattern variation, presenting opportunities for future genetic study.

Social competition as a driver of phenotype-environment correlations: implications for ecology and evolution

While it is universally recognised that environmental factors can cause phenotypic trait variation via phenotypic plasticity, the extent to which causal processes operate in the reverse direction has received less consideration. In fact individuals are often active agents in determining the environments, and hence the selective regimes, they experience. There are several important mechanisms by which this can occur, including habitat selection and niche construction, that are expected to result in phenotype–environment correlations (i.e. non‐random assortment of phenotypes across heterogeneous environments). Here we highlight an additional mechanism – intraspecific competition for preferred environments – that may be widespread, and has implications for phenotypic evolution that are currently underappreciated. Under this mechanism, variation among individuals in traits determining their competitive ability leads to phenotype–environment correlation; more competitive phenotypes are able to acquire better patches. Based on a concise review of the empirical evidence we argue that competition‐induced phenotype–environment correlations are likely to be common in natural populations before highlighting the major implications of this for studies of natural selection and microevolution. We focus particularly on two central issues. First, competition‐induced phenotype–environment correlation leads to the expectation that positive feedback loops will amplify phenotypic and fitness variation among competing individuals. As a result of being able to acquire a better environment, winners gain more resources and even better phenotypes – at the expense of losers. The distinction between individual quality and environmental quality that is commonly made by researchers in evolutionary ecology thus becomes untenable. Second, if differences among individuals in competitive ability are underpinned by heritable traits, competition results in both genotype–environment correlations and an expectation of indirect genetic effects (IGEs) on resource‐dependent life‐history traits. Theory tells us that these IGEs will act as (partial) constraints, reducing the amount of genetic variance available to facilitate evolutionary adaptation. Failure to recognise this will lead to systematic overestimation of the adaptive potential of populations. To understand the importance of these issues for ecological and evolutionary processes in natural populations we therefore need to identify and quantify competition‐induced phenotype–environment correlations in our study systems. We conclude that both fundamental and applied research will benefit from an improved understanding of when and how social competition causes non‐random distribution of phenotypes, and genotypes, across heterogeneous environments.

Genetic, social and maternal contributions to Mycobacterium bovis infection status in European badgers (Meles meles)

Within host populations, individuals can vary in their susceptibility to infections and in the severity and progression of disease once infected. Though mediated through differences in behaviour, resistance or tolerance, variation in disease outcomes ultimately stems from genetic and environmental (including social) factors. Despite obvious implications for the evolutionary, ecological and epidemiological dynamics of disease traits, the relative importance of these factors has rarely been quantified in naturally infected wild animal hosts. Here, we use a long-term capture-mark-recapture study of group-living European badgers (Meles meles) to characterize genetic and environmental sources of variation in host infection status by Mycobacterium bovis, the causative agent of bovine tuberculosis (bTB). We find that genetic factors contribute to M. bovis infection status, whether measured over a lifetime or across repeated captures. In the latter case, the heritability (h² ) of infection status is close to zero in cubs and yearlings but increases in adulthood. Overall, environmental influences arising from a combination of social group membership (defined in time and space) and maternal effects appear to be more important than genetic factors. Thus, while genes do contribute to among-individual variation, they play a comparatively minor role, meaning that rapid evolution of host defences under parasite-mediated selection is unlikely (especially if selection is on young animals where h² is lowest). Conversely, our results lend further support to the view that social and early-life environments are important drivers of the dynamics of bTB infection in badger populations specifically, and of disease traits in wild hosts more generally.

Bacterial dispersal and drift drive microbiome diversity patterns within a population of feral hindgut fermenters

Studies of microbiome variation in wildlife often emphasize host physiology and diet as proximate selective pressures acting on host-associated microbiota. In contrast, microbial dispersal and ecological drift are more rarely considered. Using amplicon sequencing, we characterized the bacterial microbiome of adult female (n = 86) Sable Island horses (Nova Scotia, Canada) as part of a detailed individual-based study of this feral population. Using data on sampling date, horse location, age, parental status, and local habitat variables, we contrasted the ability of spatiotemporal, life history, and environmental factors to explain microbiome diversity among Sable Island horses. We extended inferences made from these analyses with both phylogeny-informed and phylogeny-independent null modelling approaches to identify deviations from stochastic expectations. Phylogeny-informed diversity measures were correlated with spatial and local habitat variables, but null modelling results suggested that heterogeneity in ecological drift, rather than differential selective pressures acting on the microbiome, was responsible for these correlations. Conversely, phylogeny-independent diversity measures were best explained by host spatial and social structure, suggesting that taxonomic composition of the microbiome was shaped most strongly by bacterial dispersal. Parental status was important but correlated with measures of β-dispersion rather than β-diversity (mares without foals had lower alpha diversity and more variable microbiomes than mares with foals). Our results suggest that between host microbiome variation within the Sable Island horse population is driven more strongly by bacterial dispersal and ecological drift than by differential selective pressures. These results emphasize the need to consider alternative ecological processes in the study of microbiomes.

Quantifying selection on standard metabolic rate and body mass in Drosophila melanogaster

Standard metabolic rate (SMR), defined as the minimal energy expenditure required for self-maintenance, is a key physiological trait. Few studies have estimated its relationship with fitness, most notably in insects. This is presumably due to the difficulty of measuring SMR in a large number of very small individuals. Using high-throughput flow-through respirometry and a Drosophila melanogaster laboratory population adapted to a life cycle that facilitates fitness measures, we quantified SMR, body mass, and fitness in 515 female and 522 male adults. We used a novel multivariate approach to estimate linear and nonlinear selection differentials and gradients from the variance-covariance matrix of fitness, SMR, and body mass, allowing traits specific covariates to be accommodated within a single model. In males, linear selection differentials for mass and SMR were positive and individually significant. Selection gradients were also positive but, despite substantial sample sizes, were nonsignificant due to increased uncertainty given strong SMR-mass collinearity. In females, only nonlinear selection was detected and it appeared to act primarily on body size, although the individual gradients were again nonsignificant. Selection did not differ significantly between sexes although differences in the fitness surfaces suggest sex-specific selection as an important topic for further study.

Experimental evidence for stabilizing selection on virulence in a bacterial pathogen

The virulence‐transmission trade‐off hypothesis has provided a dominant theoretical basis for predicting pathogen virulence evolution, but empirical tests are rare, particularly at pathogen emergence. The central prediction of this hypothesis is that pathogen fitness is maximized at intermediate virulence due to a trade‐off between infection duration and transmission rate. However, obtaining sufficient numbers of pathogen isolates of contrasting virulence to test the shape of relationships between key pathogen traits, and doing so without the confounds of evolved host protective immunity (as expected at emergence), is challenging. Here, we inoculated 55 isolates of the bacterial pathogen, Mycoplasma gallisepticum, into non‐resistant house finches (Haemorhous mexicanus) from populations that have never been exposed to the disease. Isolates were collected over a 20‐year period from outbreak in disease‐exposed populations of house finches and vary markedly in virulence. We found a positive linear relationship between pathogen virulence and transmission rate to an uninfected sentinel, supporting the core assumption of the trade‐off hypothesis. Further, in support of the key prediction, there was no evidence for directional selection on a quantitative proxy of pathogen virulence and, instead, isolates of intermediate virulence were fittest. Surprisingly, however, the positive relationship between virulence and transmission rate was not underpinned by variation in pathogen load or replication rate as is commonly assumed. Our results indicate that selection favors pathogens of intermediate virulence at disease emergence in a novel host species, even when virulence and transmission are not linked to pathogen load.

Heritability and correlations among learning and inhibitory control traits

To understand the evolution of cognitive abilities, we need to understand both how selection acts upon them and their genetic (co)variance structure. Recent work suggests that there are fitness consequences for free-living individuals with particular cognitive abilities. However, our current understanding of the heritability of these abilities is restricted to domesticated species subjected to artificial selection. We investigated genetic variance for, and genetic correlations among four cognitive abilities: inhibitory control, visual and spatial discrimination, and spatial ability, measured on >450 pheasants, Phasianus colchicus, over four generations. Pheasants were reared in captivity but bred from adults that lived in the wild and hence, were subject to selection on survival. Pheasant chicks are precocial and were reared without parents, enabling us to standardize environmental and parental care effects. We constructed a pedigree based on 15 microsatellite loci and implemented animal models to estimate heritability. We found moderate heritabilities for discrimination learning and inhibitory control (h2 = 0.17-0.23) but heritability for spatial ability was low (h2 = 0.09). Genetic correlations among-traits were largely positive but characterized by high uncertainty and were not statistically significant. Principle component analysis of the genetic correlation matrix estimate revealed a leading component that explained 69% of the variation, broadly in line with expectations under a general intelligence model of cognition. However, this pattern was not apparent in the phenotypic correlation structure which was more consistent with a modular view of animal cognition. Our findings highlight that the expression of cognitive traits is influenced by environmental factors which masks the underlying genetic structure.

Choice consequences: salinity preferences and hatchling survival in the mangrove rivulus (Kryptolebias marmoratus)

In heterogeneous environments, mobile species should occupy habitats in which their fitness is maximized. Mangrove rivulus fish inhabit mangrove ecosystems where salinities range from 0 to 65 ppt, but are most often collected from areas with salinities of ∼25 ppt. We examined the salinity preference of mangrove rivulus in a lateral salinity gradient, in the absence of predators and competitors. Fish could swim freely for 8 h throughout the gradient with chambers containing salinities ranging from 5 to 45 ppt (or 25 ppt throughout in the control). We defined preference as the salinity in which the fish spent most of their time, and also measured preference strength, latency to begin exploring the arena, and number of transitions between chambers. To determine whether these traits were repeatable, each fish experienced three trials. Mangrove rivulus spent a greater proportion of time in salinities lower (5-15 ppt) than they occupy in the wild. Significant among-individual variation in the (multivariate) behavioral phenotype emerged when animals experienced the gradient, indicating strong potential for selection to drive behavioral evolution in areas with diverse salinity microhabitats. We also showed that mangrove rivulus had a significantly greater probability of laying eggs in low salinities compared with control or high salinities. Eggs laid in lower salinities also had higher hatching success compared with those laid in higher salinities. Thus, although mangrove rivulus can tolerate a wide range of salinities, they prefer low salinities. These results raise questions about factors that prevent mangrove rivulus from occupying lower salinities in the wild, whether higher salinities impose energetic costs, and whether fitness changes as a function of salinity.

Analysis of direct and indirect genetic effects in fighting sea anemones

Theoretical models of animal contests such as the Hawk-Dove game predict that variation in fighting behavior will persist due to mixed evolutionarily stable strategies (ESS) under certain conditions. However, the genetic basis for this variation is poorly understood and a mixed ESS for fighting can be interpreted in more than one way. Specifically, we do not know whether variation in aggression within a population arises from among-individual differences in fixed strategy (determined by an individual's genotype-direct genetic effects [DGEs]), or from within-individual variation in strategy across contests. Furthermore, as suggested by developments of the original Hawk-Dove model, within-individual variation in strategy may be dependent on the phenotype and thus genotype of the opponent (indirect genetic effects-IGEs). Here we test for the effect of DGEs and IGEs during fights in the beadlet sea anemone Actinia equina. By exploiting the unusual reproductive system of sea anemones, combined with new molecular data, we investigate the role of both additive (DGE + IGE) and non-additive (DGE × IGE) genetic effects on fighting parameters, the latter of which have been hypothesized but never tested for explicitly. We find evidence for heritable variation in fighting ability and that fight duration increases with relatedness. Fighting success is influenced additively by DGEs and IGEs but we found no evidence for non-additive IGEs. These results indicate that variation in fighting behavior is driven by additive indirect genetic effects (DGE + IGE), and support a core assumption of contest theory that strategies are fixed by DGEs.

Genetic variance for behavioural 'predictability' of stress response

Genetic factors underpinning phenotypic variation are required if natural selection is to result in adaptive evolution. However, evolutionary and behavioural ecologists typically focus on variation among individuals in their average trait values and seek to characterize genetic contributions to this. As a result, less attention has been paid to if and how genes could contribute towards within-individual variance or trait 'predictability'. In fact, phenotypic 'predictability' can vary among individuals, and emerging evidence from livestock genetics suggests this can be due to genetic factors. Here, we test this empirically using repeated measures of a behavioural stress response trait in a pedigreed population of wild-type guppies. We ask (a) whether individuals differ in behavioural predictability and (b) whether this variation is heritable and so evolvable under selection. Using statistical methodology from the field of quantitative genetics, we find support for both hypotheses and also show evidence of a genetic correlation structure between the behavioural trait mean and individual predictability. We show that investigating sources of variability in trait predictability is statistically tractable and can yield useful biological interpretation. We conclude that, if widespread, genetic variance for 'predictability' will have major implications for the evolutionary causes and consequences of phenotypic variation.

The problem of measuring trait-preference correlations without disrupting them

A key element at the heart of the Fisher–Lande–Kirkpatrick model of the sexual selection process is the genetic correlation between (male) trait and (female) preference. The strength of this association is critical in determining a population’s evolutionary trajectory, which is why estimating its magnitude is so important. In the Lande model, the trait-preference correlation is solely established and maintained by mate choice, and although it is unclear how exclusively mate choice does this in nature, the experimental designs typically employed to measure trait-preference genetic correlations could be systematically weakening estimates by not allowing free mate choice (similarly with husbandry practices). The precise impact of the problem is unknown, and possibly unknowable, but simple solutions can be applied to ensure the accuracy of trait-preference correlation estimates is maximized.

Ejaculate-mediated paternal effects: evidence, mechanisms and evolutionary implications

Despite serving the primary objective of ensuring that at least one sperm cell reaches and fertilises an ovum, the male ejaculate (i.e. spermatozoa and seminal fluid) is a compositionally complex 'trait' that can respond phenotypically to subtle changes in conditions. In particular, recent research has shown that environmentally and genetically induced changes to ejaculates can have implications for offspring traits that are independent of the DNA sequence encoded into the sperm's haploid genome. In this review, we compile evidence from several disciplines and numerous taxonomic systems to reveal the extent of such ejaculate-mediated paternal effects (EMPEs). We consider a number of environmental and genetic factors that have been shown to impact offspring phenotypes via ejaculates, and where possible, we highlight the putative mechanistic pathways by which ejaculates can act as conduits for paternal effects. We also highlight how females themselves can influence EMPEs, and in some cases, how maternally derived sources of variance may confound attempts to test for EMPEs. Finally, we consider a range of putative evolutionary implications of EMPEs and suggest a number of potentially useful approaches for exploring these further. Overall, our review confirms that EMPEs are both widespread and varied in their effects, although studies reporting their evolutionary effects are still in their infancy.

Quantitative genetics of gastrointestinal strongyle burden and associated body condition in feral horses

Variability in host resistance or tolerance to parasites is nearly ubiquitous, and is of key significance in understanding the evolutionary processes shaping host-parasite interactions. While ample research has been conducted on the genetics of parasite burden in livestock, relatively little has been done in free-living populations. Here, we investigate the sources of (co)variation in strongyle nematode faecal egg count (FEC) and body condition in Sable Island horses, a feral population in which parasite burden has previously been shown to negatively correlate with body condition. We used the quantitative genetic "animal model" to understand the sources of (co)variation in these traits, and tested for impacts of an important spatial gradient in habitat quality on the parameter estimates. Although FEC is significantly heritable (h ² = 0.43 ± 0.11), there was no evidence for significant additive genetic variation in body condition (h ² = 0.04 ± 0.07), and therefore there was also no significant genetic covariance between the two traits. The negative phenotypic covariance between these traits therefore does not derive principally from additive genetic effects. We also found that both FEC and body condition increase from east to west across the island, which indicates that the longitudinal environmental gradient is not responsible for the negative phenotypic association observed between these traits. There was also little evidence to suggest that quantitative genetic parameters were biased when an individual's location along the island's environmental gradient was not incorporated into the analysis. This research provides new and important insights into the genetic basis and adaptive potential of parasite resistance in free-living animals, and highlights the importance of environmental heterogeneity in modulating host-parasite interactions in wild vertebrate systems.

Individual variation and the source-sink group dynamics of extra-group paternity in a social mammal

Movement of individuals, or their genes, can influence eco-evolutionary processes in structured populations. We have limited understanding of the extent to which spatial behavior varies among groups and individuals within populations. Here, we use genetic pedigree reconstruction in a long-term study of European badgers (Meles meles) to characterize the extent of extra-group paternity, occurring as a consequence of breeding excursions, and to test hypothesized drivers of variation at multiple levels. We jointly estimate parentage and paternity distance (PD; distance between a cub's natal and its father's social group), and test whether population density and sex ratio influence mean annual PD. We also model cub-level PD and extra-group paternity (EGP) to test for variation among social groups and parental individuals. Mean PD varied among years but was not explained by population density or sex ratio. However, cub-level analysis shows strong effects of social group, and parental identities, with some parental individuals being consistently more likely to produce cubs with extra-group partners. Group effects were partially explained by local sex ratio. There was also a strong negative correlation between maternal and paternal social group effects on cub paternity distance, indicating source-sink dynamics. Our analyses of paternity distance and EGP indicate variation in extra-group mating at multiple levels-among years, social groups and individuals. The latter in particular is a phenomenon seldom documented and suggests that gene flow among groups may be disproportionately mediated by a nonrandom subset of adults, emphasizing the importance of the individual in driving eco-evolutionary dynamics.

The role of indirect genetic effects in the evolution of interacting reproductive behaviors in the burying beetle, Nicrophorus vespilloides

Social interactions can give rise to indirect genetic effects (IGEs), which occur when genes expressed in one individual affect the phenotype of another individual. The evolutionary dynamics of traits can be altered when there are IGEs. Sex often involves indirect effects arising from first-order (current) or second-order (prior) social interactions, yet IGEs are infrequently quantified for reproductive behaviors. Here, we use experimental populations of burying beetles that have experienced bidirectional selection on mating rate to test for social plasticity and IGEs associated with focal males mating with a female either without (first-order effect) or with (second-order effect) prior exposure to a competitor, and resource defense behavior (first-order effect). Additive IGEs were detected for mating rate arising from (first-order) interactions with females. For resource defense behavior, a standard variance partitioning analysis provided no evidence of additive genetic variance-either direct or indirect. However, behavior was predicted by focal size relative to that of the competitor, and size is also heritable. Assuming that behavior is causally dependent on relative size, this implies that both DGEs and IGEs do occur (and may potentially interact). The relative contribution of IGEs may differ among social behaviors related to mating which has consequences for the evolutionary trajectories of multivariate traits.

Habituation and individual variation in the endocrine stress response in the Trinidadian guppy (Poecilia reticulata)

The vertebrate stress response enables individuals to react to and cope with environmental challenges. A crucial aspect of the stress response is the elevation of circulating glucocorticoids. However, continued activation of the stress response under repeated exposure to stressors can be damaging to fitness. Under certain circumstances it may therefore be adaptive to habituate to repeated exposures to a particular stressor by reducing the magnitude of any associated release of glucocorticoids. Here, we investigate whether Trinidadian guppies (Poecilia reticulata) habituate to repeated exposure to a mild stressor, using a waterborne hormone sampling approach that has previously been shown to elicit a stress response in small fish. We also test for individual variation in the extent of habituation to this stressor. Concentrating on freely circulating cortisol, we found that the first exposure to the assay induced high cortisol release rates but that guppies tended to habituate quickly to subsequent exposures. There were consistent differences among individuals in their average cortisol release rate (after accounting for effects of variables such as body size) over repeated exposures. Our analyses did not find evidence of individual differences in habituation rate, although limitations in statistical power could account for this finding. We repeated the analysis for free 11-ketotestosterone, which can also respond to stressors, but found no obvious habituation pattern and no among-individual variation. We also present data on conjugated forms of both hormones, which were repeatable but did not show the expected time-lagged habituation effect. We discuss consistent individual differences around the general pattern of habituation in the flexible stress response, and highlight the potential for individual variation in habituation to facilitate selection against the deleterious effects of chronic stress.

Genotype-by-sex-by-diet interactions for nutritional preference, dietary consumption, and lipid deposition in a field cricket

Changes in feeding behaviour, especially the overconsumption of calories, has led to a rise in the rates of obesity, diabetes, and other associated disorders in humans and a range of animals inhabiting human-influenced environments. However, understanding the relative contribution of genes, the nutritional environment, and their interaction to dietary intake and lipid deposition in the sexes still remains a major challenge. By combining nutritional geometry with quantitative genetics, we determined the effect of genes, the nutritional environment, and their interaction on the total nutritional preference (TP), total diet eaten (TE), and lipid mass (LM) of male and female black field crickets (Teleogryllus commodus) fed one of four diet pairs (DPs) differing in the ratio of protein to carbohydrate and total nutritional content. We found abundant additive genetic variance for TP, TE, and LM in both sexes and across all four DPs, with significant genetic correlations between TE and TP and between TP and LM in males. We also found significant genotype-by-DP and genotype-by-sex-by-DP interactions for each trait and significant genotype-by-sex interactions for TE and LM. Complex interactions between genes, sex, and the nutritional environment, therefore, play an important role in nutrient regulation and lipid deposition in T. commodus. This finding may also help explain the increasing rate of obesity and the maintenance of sex differences in obesity observed across many animal species, including humans.

Towards using a focussed phased array of millimetre length scale elements for ultrasound imaging

Sparse phased array ultrasound transducers with millimetre length scale elements have previously been proposed for generating hyperthermia but not for imaging. Numerical simulation with a pseudospectral solver was used to investigate: (a) how the position of the maximum pressure in the focal region changed with element diameter and frequency; (b) how the size and position of the focal region changed with focal distance under steering; and (c) the imaging performance of 15 element random arrays. These analyses were performed for both piston-like and non piston-like millimetre diameter elements since previous work has shown a shift in the distance to the maximum pressure in the focal region with the latter. The results for these elements were compared with elements where the diameter was  <λ/2. The distance from the array to the position of maximum pressure in the focal region diverged from the value with element diameter  <λ/2; values for piston-like elements increased positively whilst values for non piston-like elements increased negatively. With distances expressed in λ, no difference was found for arrays at 1 MHz and 2.5 MHz. For piston-like elements, but not for non piston-like elements, two peaks were found in the focal region which were in-line with the direction of propagation for a focus on the central axis but which rotated to become parallel with the direction of propagation when steering exceeded 20°. The size and position of the focal region under steering was similar for the non piston-like elements and elements with diameter  <λ/2. Little difference was found in image quality or the size of the point spread function (PSF) between images at 2.5 MHz with piston-like and non piston-like behaviour for steering angles less than 20° when compared with a linear array of similar size. These results suggest that imaging with random arrays of millimetre length scale elements is possible.

Behavioural mediators of genetic life-history trade-offs: a test of the pace-of-life syndrome hypothesis in field crickets

The pace-of-life syndrome (POLS) hypothesis predicts associations between life history and 'risky' behaviours. Individuals with 'fast' lifestyles should develop faster, reproduce earlier, exhibit more risk-prone behaviours, and die sooner than those with 'slow' lifestyles. While support for POLS has been equivocal to date, studies have relied on individual-level (phenotypic) patterns in which genetic trade-offs may be masked by environmental effects on phenotypes. We estimated genetic correlations between life history (development, lifespan, size) and risky behaviours (exploration, aggression) in a pedigreed population of Mediterranean field crickets (Gryllus bimaculatus). Path analyses showed that behaviours mediated some genetic relationships between life history traits, though not those involved in trade-offs. Thus, while specific predictions of POLS theory were not supported, genetic integration of behaviour and life history was present. This implies a major role for risky behaviours in life history evolution.

Ontogeny of the morphology-performance axis in an amphibious fish (Kryptolebias marmoratus)

Establishing links between morphology and performance is important for understanding the functional, ecological, and evolutionary implications of morphological diversity. Relationships between morphology and performance are expected to be age dependent if, at different points during ontogeny, animals must perform in different capacities to achieve high fitness returns. Few studies have examined how the relationship between form and function changes across ontogeny. Here, we assess this relationship in the amphibious mangrove rivulus (Kryptolebias marmoratus) fish, a species that is both capable of and reliant on "tail-flip jumping" for terrestrial locomotion. Tail-flip jumping entails an individual transferring its weight to the caudal region of the body, launching itself from the substrate to navigate to new aquatic or semi-aquatic habitats. By combining repeated trials of jumping performance in 237 individuals from distinct age classes with a clearing and staining procedure to visualize bones in the caudal region, we test the hypotheses that as age increases (i) average jumping performance (body lengths jumped) will increase, (ii) the amount of variation for each trait will change, and (iii) the patterns of covariation/correlation among traits, which tell us about the integration of form with function, will also change. We find a significant increase in size-adjusted jumping performance with age, and modification to the correlation structure among traits across ontogeny. However, we also find that significant links between form and function evident in young animals disappear at later ontogenetic stages. Our study suggests that different functional mechanisms may be associated with high performance at different stages of development.

Early Experience of Intraoperative Autotransfusion

Intraoperative autotransfusion of whole blood was performed using the Solcotrans device in 45 patients undergoing major vascular surgery or other procedures in which there was a clean operative field. Overall, 60% of the blood shed during these operations was reinfused. Approximately 50% of patients avoided the potential complications of homologous transfusion. There were no complications attributable to the use of this device although in a sample of 13 patients, 30% of the erythrocytes were haemolysed and there were other minor haematological abnormalities. In conclusion this device provides a simple method of autotransfusing 2 or 3 litres of blood aspirated from an uncontaminated operative field.

Testing the stability of behavioural coping style across stress contexts in the Trinidadian guppy

Within populations, individuals can vary in stress response, a multivariate phenomenon comprising neuroendocrine, physiological and behavioural traits.Verbal models of individual stress "coping style" have proposed that the behavioural component of this variation can be described as a single axis, with each individual's coping style being consistent across time and stress contexts.Focusing on this behavioural component of stress response and combining repeated measures of multiple traits with a novel multivariate modelling framework, we test for the existence of coping style variation and assess its stability across contexts in the Trinidadian guppy (Poecilia reticulata).Specifically, we test the following hypotheses: (1) there exists repeatable among-individual behavioural (co)variation ("personality") within a mild stress context consistent with a risk-averse-risk-prone continuum of behavioural coping style, (2) there is population-level plasticity in behaviour as a function of stressor severity, (3) there is among-individual variation in plasticity (i.e. IxE), and (4) the presence of IxE reduces cross-context stability of behavioural coping style.We found significant repeatable among-individual behavioural (co)variation in the mild stress context (open field trial), represented as an I matrix. However, I was not readily described by a simple risk-averse-risk-prone continuum as posited by the original coping style model. We also found strong evidence for population-level changes in mean behaviour with increasing stressor severity (simulated avian and piscine predation risks).Single-trait analyses did show the presence of individual-by-environment interactions (IxE), as among-individual cross-context correlations were significantly less than +1. However, multitrait analysis revealed the consequences of this plasticity variation were minimal. Specifically, we found little evidence for changes in the structure of I between mild and moderate stress contexts overall, and only minor changes between the two moderate contexts (avian vs. piscine predator).We show that a multivariate approach to assessing changes in among-individual (co)variance across contexts can prevent the over-interpretation of statistically significant, but small, individual-by-environment effects. While behavioural flexibility enables populations (and individuals) to respond rapidly to changes in the environment, multivariate personality structure can be conserved strongly across such contexts. A plain language summary is available for this article.

How should we interpret estimates of individual repeatability?

Individual repeatability (R), defined as the proportion of observed variance attributable to among-individual differences, is a widely used summary statistic in evolutionarily motivated studies of morphology, life history, physiology and, especially, behaviour. Although statistical methods to estimate R are well known and widely available, there is a growing tendency for researchers to interpret R in ways that are subtly, but importantly, different. Some view R as a property of a dataset and a statistic to be interpreted agnostically with respect to mechanism. Others wish to isolate the contributions of 'intrinsic' and/or 'permanent' individual differences, and draw a distinction between true (intrinsic) and pseudo-repeatability arising from uncontrolled extrinsic effects. This latter view proposes a narrower, more mechanistic interpretation, than the traditional concept of repeatability, but perhaps one that allows stronger evolutionary inference as a consequence (provided analytical pitfalls are successfully avoided). Neither perspective is incorrect, but if we are to avoid confusion and fruitless debate, there is a need for researchers to recognise this dichotomy, and to ensure clarity in relation to how, and why, a particular estimate of R is appropriate in any case.

Evidence for Selection-by-Environment but Not Genotype-by-Environment Interactions for Fitness-Related Traits in a Wild Mammal Population

How do environmental conditions influence selection and genetic variation in wild populations? There is widespread evidence for selection-by-environment interactions (S*E), but we reviewed studies of natural populations estimating the extent of genotype-by-environment interactions (G*E) in response to natural variation in environmental conditions and found that evidence for G*E appears to be rare within single populations in the wild. Studies estimating the simultaneous impact of environmental variation on both selection and genetic variation are especially scarce. Here, we used 24 years of data collected from a wild Soay sheep population to quantify how an important environmental variable, population density, impacts upon (1) selection through annual contribution to fitness and (2) expression of genetic variation, in six morphological and life history traits: body weight, hind leg length, parasite burden, horn length, horn growth, and testicular circumference. Our results supported the existence of S*E: selection was stronger in years of higher population density for all traits apart from horn growth, with directional selection being stronger under more adverse conditions. Quantitative genetic models revealed significant additive genetic variance for body weight, leg length, parasite burden, horn length, and testes size, but not for horn growth or our measure of annual fitness. However, random regression models found variation between individuals in their responses to the environment in only three traits, and did not support the presence of G*E for any trait. Our analyses of St Kilda Soay sheep data thus concurs with our cross-study review that, while natural environmental variation within a population can profoundly alter the strength of selection on phenotypic traits, there is less evidence for its effect on the expression of genetic variance in the wild.

Paediatric physeal sparing posterior cruciate ligament (PCL) reconstruction with parental donation allograft: Rationale and operative approach

BACKGROUND

Paediatric PCL injuries are rare but constitute a significant management challenge. We describe a novel approach to the surgical management of an 11-year-old boy who presented with persisting symptomatic instability following 18months of failed conservative therapy.

METHODS

PCL reconstruction was performed using a physeal sparing, all-inside technique under fluoroscopic control. This avoids the potential for iatrogenic growth injury. A parentally donated hamstrings allograft was used to ensure adequate graft size, and reinforced using a non-elastic two millimetre braided suture. Graft reinforcement safeguards against stretching during the early healing phase, but must be removed thereafter to avoid creating a physeal tether.

RESULTS

At three months, clinical examination under anaesthesia showed equivalent PCL laxity in the operated knee compared to the normal contralateral knee. The graft reinforcement tape was incised as planned with no change in laxity assessment. Arthroscopic evaluation demonstrated a quiet joint with a well healed graft and no synovitis. Postoperative long leg radiographs showed no growth deformity against preoperative status.

CONCLUSION

In paediatric patients with persisting symptomatic instability despite appropriate conservative management, surgical reconstruction of the PCL should be considered. Standard treatment has higher complication rates and poorer graft survival than in an adult cohort. Specific problems include iatrogenic growth plate injury causing growth arrest or angular deformity, inadequate graft size if using hamstrings autograft, and the additional technical challenge of small patient size. Early results from extra-physeal, all-inside PCL reconstruction using a parentally donated allograft are promising and may provide an alternative solution to traditional surgical management.

Phenotypic and genetic integration of personality and growth under competition in the sheepshead swordtail, Xiphophorus birchmanni

Competition for resources including food, physical space, and potential mates is a fundamental ecological process shaping variation in individual phenotype and fitness. The evolution of competitive ability, in particular social dominance, depends on genetic (co)variation among traits causal (e.g., behavior) or consequent (e.g., growth) to competitive outcomes. If dominance is heritable, it will generate both direct and indirect genetic effects (IGE) on resource‐dependent traits. The latter are expected to impose evolutionary constraint because winners necessarily gain resources at the expense of losers. We varied competition in a population of sheepshead swordtails, Xiphophorus birchmanni, to investigate effects on behavior, size, growth, and survival. We then applied quantitative genetic analyses to determine (i) whether competition leads to phenotypic and/or genetic integration of behavior with life history and (ii) the potential for IGE to constrain life history evolution. Size, growth, and survival were reduced at high competition. Male dominance was repeatable and dominant individuals show higher growth and survival. Additive genetic contributions to phenotypic covariance were significant, with the G matrix largely recapitulating phenotypic relationships. Social dominance has a low but significant heritability and is strongly genetically correlated with size and growth. Assuming causal dependence of growth on dominance, hidden IGE will therefore reduce evolutionary potential.

Island tameness and the repeatability of flight initiation distance in a large herbivore

Antipredator behaviours can be lost relatively quickly in populations that are relieved of predation, as is known for several species inhabiting islands. Flight initiation distance (FID) is often studied in the context of island tameness; however, little is known about the factors that influence and maintain FID variation in predation-free populations. Here, we studied FID in foals of an isolated predator-free population of feral horses (Equus caballus L., 1758) on Sable Island, Canada, to determine if FID could be used for research on consistent individual differences in risk aversion and island tameness. In addition to testing for temporal, spatial, and sex effects on FID, we compared repeatability estimates at two temporal scales (within and among days). Similar FID for measurements obtained on the same day and for males and females indicated an absence of short-term desensitization and sex effects. In contrast, FID decreased for measurements made on subsequent days and from east to west, which could reflect habituation to human presence and (or) other temporal and spatial processes. Repeatability was high (0.42 ± 0.06), but tended to decrease with increasing time intervals. This study highlights the potential of FID for individual-based research on the ecology and evolutionary dynamics of risk aversion in predation-free populations.

Little evidence for intralocus sexual conflict over the optimal intake of nutrients for life span and reproduction in the black field cricket Teleogryllus commodus

There is often large divergence in the effects of key nutrients on life span (LS) and reproduction in the sexes, yet nutrient intake is regulated in the same way in males and females given dietary choice. This suggests that the sexes are constrained from feeding to their sex‐specific nutritional optima for these traits. Here, we examine the potential for intralocus sexual conflict (IASC) over optimal protein and carbohydrate intake for LS and reproduction to constrain the evolution of sex‐specific nutrient regulation in the field cricket, Teleogryllus commodus. We show clear sex differences in the effects of protein and carbohydrate intake on LS and reproduction and strong positive genetic correlations between the sexes for the regulated intake of these nutrients. However, the between‐sex additive genetic covariance matrix had very little effect on the predicted evolutionary response of nutrient regulation in the sexes. Thus, IASC appears unlikely to act as an evolutionary constraint on sex‐specific nutrient regulation in T. commodus. This finding is supported by clear sexual dimorphism in the regulated intake of these nutrients under dietary choice. However, nutrient regulation did not coincide with the nutritional optima for LS or reproduction in either sex, suggesting that IASC is not completely resolved in T. commodus.

Blood-feeding patterns of native mosquitoes and insights into their potential role as pathogen vectors in the Thames estuary region of the United Kingdom

BACKGROUND

The range of vertebrate hosts on which species of mosquito blood-feed is an important parameter for identifying potential vectors and in assessing the risk of incursion and establishment of vector-borne pathogens. In the United Kingdom, studies of mosquito host range have collected relatively few specimens and used techniques that could only broadly identify host species. This study conducted intensive collection and analysis of mosquitoes from a grazing marsh environment in southeast England. This site provides extensive wetland habitat for resident and migratory birds and has abundant human nuisance biting mosquitoes. The aim was to identify the blood-feeding patterns of mosquito species present at the site which could contribute to the transmission of pathogens.

METHODS

Twice-weekly collections of mosquitoes were made from Elmley Nature Reserve, Kent, between June and October 2014. Mosquitoes were collected using resting boxes, by aspiration from man-made structures and using a Mosquito Magnet Pro baited with 1-octen-3-ol. Blood-fed specimens were classified according to the degree of blood meal digestion using the Sella scale and vertebrate origin determined using sequencing of a fragment of the mitochondrial cytochrome C oxidase subunit I gene. Mosquitoes that were morphologically cryptic were identified to species level using multiplex PCR and sequencing methods.

RESULTS

A total of 20,666 mosquitoes of 11 species were collected, and 2,159 (10.4%) were blood-fed (Sella scale II-VI); of these 1,341 blood-fed specimens were selected for blood meal analysis. Vertebrate origin was successfully identified in 964 specimens (72%). Collections of blood-fed individuals were dominated by Anopheles maculipennis complex (73.5%), Culiseta annulata (21.2%) and Culex pipiens form pipiens (10.4%). Nineteen vertebrate hosts comprising five mammals and 14 birds were identified as hosts for mosquitoes, including two migratory bird species. Feeding on birds by Culex modestus and Anopheles atroparvus populations in England was demonstrated.

CONCLUSIONS

This study expands the vertebrate host range of mosquitoes in the Thames estuary region of the UK. Feeding on both resident and migratory bird species by potential arbovirus vectors including Cx. pipiens f. pipiens and Cx. modestus indicates the potential for enzootic transmission of an introduced arbovirus between migratory and local bird species by native mosquito species.