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Simple Summary Parrondo’s paradox, whereby losing strategies or deleterious effects can combine to provide a winning outcome, has been increasingly applied by biologists to explain complex adaptations in many living systems. Here, we suggest that considering this paradox in oncology, particularly in relation to the phenotypic diversity of malignant cells, could also be a promising approach to understand several puzzling aspects of cancer biology. For example, the high genetic and epigenetic instability of cancer cells, their metastatic behavior and their capacity to enter dormancy could be explained by Parrondo’s theory. We also discuss the relevance of Parrondo’s paradox in a therapeutical framework using different examples. This work provides a compelling argument that the traditional separation between medicine and other disciplines remains a fundamental limitation that needs to be overcome if complex processes, such as oncogenesis, are to be completely understood. Abstract Many aspects of cancer biology remain puzzling, including the proliferative and survival success of malignant cells in spite of their high genetic and epigenetic instability as well as their ability to express migrating phenotypes and/or enter dormancy despite possible fitness loss. Understanding the potential adaptive value of these phenotypic traits is confounded by the fact that, when considered separately, they seem to be rather detrimental at the cell level, at least in the short term. Here, we argue that cancer’s biology and success could frequently be governed by processes underlying Parrondo’s paradox, whereby combinations of intrinsically losing strategies may result in winning outcomes. Oncogenic selection would favor Parrondo’s dynamics because, given the environmental adversity in which malignant cells emerge and evolve, alternating between various less optimal strategies would represent the sole viable option to counteract the changing and deleterious environments cells are exposed to during tumorigenesis. We suggest that malignant processes could be viewed through this lens, and we discuss how Parrondo’s principles are also important when designing therapies against cancer.

In humans, the attitude toward risk is not neutral and is dissimilar between bets involving gains and bets involving losses. The existence and prevalence of these decision features in non-human primates are unclear. In addition, only a few studies have tried to simulate the evolution of agents based on their attitude toward risk. Therefore, we still ignore to what extent Prospect theory’s claims are evolutionarily rooted. To shed light on this issue, we collected data from nine macaques that performed bets involving gains or losses. We confirmed that their overall behaviour is coherent with Prospect theory’s claims. In parallel, we used a genetic algorithm to simulate the evolution of a population of agents across several generations. We showed that the algorithm selects progressively agents that exhibit risk-seeking, and has an inverted S-shape distorted perception of probability. We compared these two results and found that monkeys’ attitude toward risk is only congruent with the simulation when they are facing losses. This result is consistent with the idea that gambling in the loss domain is analogous to deciding in a context of life-threatening challenges where a certain level of risk-seeking behaviour and probability distortion may be adaptive. This article is part of the theme issue ‘Existence and prevalence of economic behaviours among non-human primates’.

Telomere length is correlated positively with longevity at the individual level, but negatively when compared across species. Here, we tested the association between lifespan and telomere length in African annual killifish. We analyzed telomere length in 18 Nothobranchius strains derived from diverse habitats and measured the laboratory lifespan of 14 strains of N. furzeri and N. kadleci. We found that males had shorter telomeres than females. The longest telomeres were recorded in strains derived from dry region where male lifespans were shortest. At the individual level, we detected a weak negative association between rapid juvenile growth and shorter telomeres in early adulthood. Overall, average telomere length was a good descriptor of telomere length distribution. However, within-individual telomere length spread was not related to any pattern. This substantial variation in telomere length between strains from different environments provides killifish as powerful tool to understand the evolutionarily adaptive value of telomere length.

Heterothermy allows organisms to cope with fluctuating environmental conditions. The use of regulated hypometabolism allows seasonal heterothermic species to cope with annual resource shortages and thus to maximize survival during the unfavorable season. This comes with deep physiological remodeling at each seasonal transition to allow the organism to adjust to the changing environment. In the wild, this adaptation is highly beneficial and largely overcomes potential costs. However, researchers recently proposed that it might also generate both ecological and physiological costs for the organism. Here, we propose new perspectives to be considered when analyzing adaptation to seasonality, in particular considering these costs. We propose a list of putative costs, including DNA damage, inflammatory response to fat load, brain and cognitive defects, digestive malfunction and immunodeficiency, that should receive more attention in future research on physiological seasonality. These costs may only be marginal at each transition event but accumulate over time and therefore emerge with age. In this context, studies in captivity, where we have access to aging individuals with limited extrinsic mortality (e.g., predation), could be highly valuable to experimentally assess the costs of physiological flexibility. Finally, we offer new perspectives, which should be included in demographic models, on how the adaptive value of physiological flexibility could be altered in the future in the context of global warming.

International audience; Social influences on vocal development of young birds have been widely studied in oscine songbirds who learn to sing by vocal imitation of conspecifics, mainly male adults. In contrast, vocal development of non-vocal learners such as Galliformes is considered as being under strong genetic influence and independent of the social environment. In this study, we investigated the role of the mother on the vocal development of young Japanese quail (Coturnix coturnix japonica). We compared the vocal development of mothered and non-mothered chicks during the first 21 days of life. We analysed the structural changes of two vocalisations: a) the rally call, emitted during long-distance communication and in stressful situations, b) the contact call, emitted during short-distance communication when chicks are in visual and/or auditory contact with congeners. We showed that temporal and spectral structures of the two types of calls changed during development and differed between mothered and nonmothered chicks. These results demonstrate that maternal presence influences the vocal development of the young in the Japanese quail. Even if the adaptive value of such changes was not assessed, these results highlight that plasticity of vocalisations in species considered as non-vocal learners has been underestimated.

International audience; The adaptive value of correlations among phenotypic traits depends on the prevailing environmental conditions. Differences in selection pressures during species range expansions may therefore shape phenotypic integration. In this study, we assessed variation in behavioral and morphological traits, as well as their covariations, in replicated southern and northern European populations of the northward expanding dragonfly Crocothemis erythraea. Larvae from northern populations were, on average, darker in color, and therefore, better camouflaged than larvae from southern populations. However, there was no difference in activity level. Darkness and activity were positively correlated in larvae from northern populations, whereas this trait covariation was missing in southern populations. These findings indicate the emergence of alternative strategies in time-limited northern populations, a higher activity level that required better camouflage through darker coloration, while less active larvae benefited from an energy-saving strategy by reducing the investment in costly traits, such as body darkness. We further found that larger larvae emerged into larger adults, with a higher investment in flight morphology. Our findings imply that phenotypic integration is associated with the northward range shift, potentially differentially shaping fitness consequences, and ecological interactions in southern versus northern populations.

Understanding the evolution of complex traits is among the major challenges in biology. One such trait is the cuticular hydrocarbon (CHC) layer in insects. It protects against desiccation and provides communication signals, especially in social insects. CHC composition is highly diverse within and across species. To understand the adaptive value of this chemical diversity, we must understand how it affects biological functionality. So far, CHCs received ample research attention, but their physical properties were little studied. We argue that these properties determine their biological functionality, and are vital to understand how CHC composition affects their adaptive value. We investigated melting behaviour and viscosity of CHCs from eleven ant species using differential scanning calorimetry and a novel microrheological technique. Cuticular hydrocarbons began melting below -45°C, and often were entirely liquid only above 30°C. Thus, they formed a solid-liquid mixture at ambient conditions, which contrasts to previous assumptions of entirely solid layers in many species. This may be adaptive since only biphasic CHC layers ensure uniform coating of the insect body, which is necessary for waterproofing. CHC viscosity was mostly between 0.1 and 0.2 Pa.s, thus similar to motor oils. Surprisingly, chemically different CHC profiles had similar viscosities, suggesting that a certain viscosity level is adaptive and ensures that communication signals can be perceived. With this study, we draw attention to the importance of studying the physics of CHC layers. Only by understanding how chemical and physical mechanisms enable CHC functionality can we understand the causes and consequences of CHC diversification.

Color patterns provide easy access to phenotypic diversity and allow the questioning of the adaptive value of traits or the constraints acting on phenotypic evolution. Reef fish offer a unique opportunity to address such questions because they are ecologically and phylogenetically diverse and have the largest variety of pigment cell types known in vertebrates. In addition to recent development of their genetic resources, reef fish also constitute experimental models that allow the discrimination of ecological, developmental, and evolutionary processes at work. Here, we emphasize how the study of color patterns in reef fish can be integrated in an Eco/Evo/Devo (ecological evolutionary developmental) perspective and we illustrate that such an approach can bring new insights on the evolution of complex phenotypes.

International audience; When, how often and for how long organisms mate can have strong consequences for individual fitness and are crucial aspects of evolutionary ecology. Such determinants are likely to be of even greater importance in monandrous species and species with short adult life stages. Previous work suggests that mobility, a key dispersal-related trait, may affect the dynamics of copulations, but few studies have investigated the impact of individual mobility on mating latency, copulation duration and oviposition latency simultaneously. In this paper, we monitored the copulation dynamics of 40 males and 40 females, as well as the oviposition dynamics of the females of the Large White butterfly Pieris brassicae, a facultative long-distance disperser butterfly. Individuals from a breeding were selected to create a uniform distribution of mobility and we recorded the timing, number and duration of all copulations in a semiexperimental system. We showed that mobility, measured as the time spent in flight under stressful conditions (a proxy of dispersal tendency), correlates with all aspects of copulation dynamics: mobile males and females mated earlier and for shorter periods than less mobile individuals. In turn, late mating females increased the time between copulation and oviposition. These results feed the previously described mobility syndrome of P. brassicae, involving morphological and physiological characters, with life-history traits. We suggest that the reduction of mating latency and copulation duration has an adaptive value in dispersing individuals, as their life expectancy might be shorter than that of sedentary individuals.

The evolution of cooperation and social behaviour is often studied in isolation from the ecology of organisms. Yet, the selective environment under which individuals evolve is much more complex in nature, consisting of ecological and abiotic interactions in addition to social ones. Here, we measured the life-history costs of cooperative chemical defence in a gregarious social herbivore, Diprion pini pine sawfly larvae, and how these costs vary under different ecological conditions. We ran a rearing experiment where we manipulated diet (resin content) and attack intensity by repeatedly harassing larvae to produce a chemical defence. We show that forcing individuals to allocate more to cooperative defence (high attack intensity) incurred a clear cost by decreasing individual survival and potency of chemical defence. Cooperative behaviour and the magnitude of its costs were further shaped by host plant quality. The number of individuals participating in group defence, immune responses and female growth decreased on a high resin diet under high attack intensity. We also found some benefits of cheating: non-defending males had higher growth rates across treatments. Taken together, these results suggest that ecological interactions can shape the adaptive value of cooperative behaviour and maintain variation in the frequency of cooperation and cheating.

International audience; Why has the use of insects as biological models in behavioural ecology been so successful? The first reason is, without question, their diversity. Class Insecta contains the largest number of species in Animalia [1]. They have colonized all terrestrial ecosystems and present a huge diversity of life history traits and behaviours that makes them fascinating organisms to answer the key historical question in behavioural ecology, that is, what is the adaptive value of observed behaviours in different environments? The second reason is their size. Thanks to their small size, and thus to our ability to rear them easily in many cases, insects always were — and still are — wonderful biological models for running laboratory experiments. Over the years, this has enabled us to address important questions related to animal behavioural ecology, leading us both to verify experimentally existing model predictions and to foster further theoretical developments. Such a strong dialogue between theoretical and experimental work on insects has greatly contributed to the development of our current knowledge of behavioural ecology in general. Since the 70s, studies on the behavioural ecology of insects have tried to understand the adaptive value of decision-making processes adopted by individuals in different environmental contexts. One striking example concerns the optimal decisions adopted by reproductive animals. This is the case, for example, for the optimal clutch size and the optimal sex ratio females should lay, or the optimal time foraging animals should remain on patches of resources. In this respect, insect parasitoids are one the most studied guilds of insects, leading to a large number of important findings (see e.g. [2–4]). This classical approach is always fruitful, and determining the adaptive value of behaviour is always at the core of this scientific field [5]. In the Special Issue, three papers illustrate such a classical approach, and develop new ideas and concepts on nutritional ecology, mate choice and polyem-bryony. Raubenheimer and Simpson present an integrative approach — nutritional geometry — that brings together two historical disciplines: foraging and feeding. Nutritional geometry allows us to model graphically and elegantly the interactions between different diet components and their effects across several levels, including physiology and ecology, on individual behaviour and reproductive success. Such a promising approach, which has yet to be used in the field in insects, should allow us to integrate all facets of nutritional activity in animals. Another classical question in behavioural ecology is sexual selection and particularly mate choice. Kelly presents recent research on the identification of factors — both intrinsic and extrinsic — of the females explaining variation in their mate preference for sexually selected traits in males. Eric Wajnberg is a population biologist, specialized in population genetics, behavioural ecology, statistical modelling and biological control. For over thirty years, he developed several scientific programmes leading to better understand what are the most important behavioural traits involved in the efficacy of insect parasitoids to control crop pests in biological control programmes. Theoretical approaches are developed — mainly using Monte Carlo simulations and Genetic Algorithms — and experiments are conducted in order to verify the predictions obtained. The main traits studied are (1) those involved in progeny and sex allocation (sex ratio), (2) locomotory mechanisms involved in discovering hosts (video tracking), (3) patch exploitation strategies, etc. He is the editor-in-chief of the international journal BioControl and has published more than 10 books on insect ecology and biological control.

International audience; Behavioural ecologists have for decades investigated the adaptive value of extra‐pair copulation (EPC) for females of socially monogamous species. Despite extensive effort testing for genetic benefits, there now seems to be a consensus that the so‐called ‘good genes’ effects are at most weak. In parallel the search for direct benefits has mostly focused on the period surrounding egg laying, thus neglecting potential correlates of EPC that might be expressed at later stages in the breeding cycle. Here we used Bayesian methods to analyse data collected over four years in a population of blue tits Cyanistes caeruleus, where no support was previously found for ‘good genes’ effects. We found that broods with mixed paternity experienced less brood failure at the nestling stage than broods with single paternity, and that females having experienced complete brood failure in their previous breeding attempt had higher rates of mixed paternity than either yearling or previously successful females. To better understand these observations we also explored relationships between extra‐pair mating, male and female phenotype, and local breeding density. We found that in almost all cases the sires of extra‐pair offspring were close neighbours, and that within those close neighbourhoods extra‐pair sires were older than other males not siring extra‐pair offspring. Also, females did not display consistent EPC status across years. Taken together our results suggest that multiple mating might be a flexible female behaviour influenced by previous breeding experience, and motivate further experimental tests of causal links between extra‐pair copulation and predation.

International audience; Most studies on avian olfactory communication have focused on mate choice, and the importance of olfaction in subsequent nesting stages has been poorly explored. In particular, the role of olfactory cues in egg recognition has received little attention, despite eggs potentially being spread with parental odorous secretions known to elicit individual discrimination. Here we used behavioral choice tests to determine whether female blue petrels (Halobaena caerulea) can discriminate the odor of their own egg from the odor of a conspecific egg. Females preferentially approached the odor of their own egg, suggesting that blue petrels can recognize their own egg using odor cues. This finding raises the question of the adaptive value of this mechanism, and may inspire further research on odor-based egg discrimination in species suffering brood parasitism.

International audience; Synchronized behaviours are found in various species, among all taxa of live beings. Being synchronized with other individuals is defined by doing the same thing, at the same time and at the same place as others. It is observed within intraspecific groups and dyads. We aim to provide a synthetic overview of what is behavioural synchronization and focus on the adaptive value of such a phenomenon among individuals. Then, as it is observed that some stable groups or dyads consist of individuals from different species, we finally propose to investigate the existence of interspecific behavioural synchronization.

International audience; Recent years have seen a growth of interest in the consistent differences in individual behaviour over time and contexts constituting so-called “individual coping styles”. An understanding of this inter-individual variation is essential to improve our knowledge of the adaptive value of behaviour. Coping styles may have implications in diverse fields, so the development of appropriate screening methods for each species appears to be the most effective way to extend our knowledge and to incorporate behavioural responses into selection-based breeding programmes, to improve the domestication and welfare of farmed fish. We tested 30 juvenile seabass (Dicentrarchus labrax) at least twice in individual-based tests (feeding recovery in isolation, aggressiveness, exploration in a T-maze and net restraint) and group-based tests (risk-taking and hypoxia sorting), to assess coping style consistency in the short and long term and between tests. The results of individual-based tests were inconsistent over time and between tests in our set-up: the time between repeat tests, learning and species-specific behavioural responses appeared to have a major impact. By contrast, the results of group-based tests, such as risk-taking and hypoxia sorting, appeared to be consistent (both in the short and long term). These tests therefore appeared to be the most relevant for the characterisation of coping style in European seabass. Furthermore, the results of these tests were also predictive of cortisol stress response. These tests are simple to perform and can be used to screen large numbers of fish, the first step in selection programmes including behavioural profiles

International audience; It is now widely acknowledged that mothers can transfer their own immune experience to their progeny through the allocation of specific maternal antibodies (hereafter referred as MatAb) that can shape offspring phenotype and affect their fitness. However, the importance of environmental variability in modulating the effects of MatAb on offspring traits is still elusive. Using an experimental approach, we investigated how food availability interacted with MatAb to solve the trade-off between humoral immunity and growth in young feral pigeons Columba livia. Results show that the inhibitory effect of MatAb on the humoral response of chicks was detected regardless of the food treatment. In addition, body mass growth was higher in chicks receiving lower amounts of maternal antibodies but only in chicks of the ad libitum food treatment. This contradicts previous studies and suggests that the transfer of MatAb could entail some costs for chicks and reduce their growth. Taken together these results reinforce the idea that the maternal antibodies play a central role in shaping offspring life-history traits but that their adaptive value is highly dependent on the environmental context in which they are transmitted by the mother.

It is expected that natural selection has endowed our auditory apparatus with the ability to adaptively prioritize information that is crucial for survival and reproduction, such as vocal emotional signals emitted by our conspecifics, even in a noisy and dynamic natural environment (signals progressively emerge or fade away in noise as conspecifics move toward or away from us). Here, we tested the hypothesis that emotional signals are detected more easily (i.e., at lower signal-to-noise levels) and retained for a longer time (i.e., persisting in your sensory system at greater distance from the physical source) than signals bearing no emotional content, using a perceptual hysteresis protocol. Trials consisted of emotional signals (i.e., laughter and screams) or neutral signals (spectrally-rotated versions of the emotional stimuli) progressively emerging from white noise (ascending sequences) or progressively fading away in white noise (descending sequences). We demonstrated that vocal emotional signals were significantly detected at lower signal-to-noise levels than emotionally neutral signals in both ascending and descending sequences, suggesting that the human auditory system prioritizes signals bearing adaptive value.

In the Neotropics, the genus Hydrangea of the popular ornamental hortensia family is represented by climbing species that strongly cling to their support surface by means of adhesive roots closely positioned along specialized anchoring stems. These root-climbing hortensia species belong to the nearly exclusive American Hydrangea section Cornidia and generally are long lianescent climbers that mostly flower and fructify high in the host tree canopy. The Mexican species Hydrangea seemannii , however, encompasses not only long lianescent climbers of large vertical rock walls and coniferous trees, but also short ‘shrub-like’ climbers on small rounded boulders. To investigate growth form plasticity in root-climbing hortensia species, we tested the hypothesis that support variability (e.g. differences in size and shape) promotes plastic responses observable at the mechanical, structural and anatomical level. Stem bending properties, architectural axis categorization, tissue organization and wood density were compared between boulder and long-vertical tree-climbers of H. seemannii . For comparison, the mechanical patterns of a closely related, strictly long-vertical tree-climbing species were investigated. Hydrangea seemannii has fine-tuned morphological, mechanical and anatomical responses to support variability suggesting the presence of two alternative root-climbing strategies that are optimized for their particular environmental conditions. Our results suggest that variation of some stem anatomical traits provides a buffering effect that regulates the mechanical and hydraulic demands of two distinct plant architectures. The adaptive value of observed plastic responses and the importance of considering growth form plasticity in evolutionary and conservation studies are discussed.

International audience; Increasing levels of anthropogenic noise represent a challenge for animals living in urban areas and birds, especially, may suffer from noisy conditions as they use singing to attract mates. Most anthropogenic noise is low in frequency and singing at high frequencies under noisy urban conditions may avoid masking and thus be a good strategy for breeding success in cities. Despite comparative, correlational and some experimental studies supporting this hypothesis, empirical studies on the impact of noise on sexual behaviour are largely lacking. Domestic canaries, Serinus canaria, provide an excellent model system to test unequivocal sexual responsiveness as receptive females perform copulation solicitation displays (CSD) to male song. We have previously shown that CSD rate was higher for low- than for high-frequency songs. In the current study, we tested whether a typical urban noise spectrum, with a bias towards low frequencies, could undermine sexual preferences. Using overlapping and alternating noise exposure regimes while broadcasting male songs we found that masking by urban noise reduced female responsiveness to low-frequency attractive songs. Under the same conditions the responsiveness to high-frequency songs remained unaffected and, consequently, the sexual preference for low- over high-frequency songs had faded because of the urban noise. We discuss to what extent our results can be extrapolated to other wild bird species and speculate about the adaptive value of the typical upward shift in frequency found in many city birds.

International audience; Local competitive interactions strongly influence plant community dynamics. To maintain their performance under competition, clonal plants may plastically modify their network architecture to grow in the direction of least interference. The adaptive value of this plastic avoidance response may depend, however, on traits linked with the plant's structural blueprint and ontogeny. We tested this hypothesis using virtual populations. We used an Individual Based Model to simulate competitive interactions among clones within a plant population. Clonal growth was studied under three competition intensities in plastic and non-plastic individuals. Plasticity buffered the negative impacts of competition at intermediate densities of competitors by promoting clone clumping. Success despite competition was promoted by traits linked with (1) the plant's structural blueprint (weak apical dominance and sympodial growth) and (2) ontogenetic processes, with an increasing or a decreasing dependence of the elongation process on the branch generation level or length along the competition intensity gradient respectively. The adaptive value of the plastic avoidance response depended on the same traits. This response only modulated their importance for clone success. Our results show that structural blueprint and ontogeny can be primary filters of plasticity and can have strong implications for evolutionary ecology, as they may explain why clonal plants have developed many species-specific plastic avoidance behaviours.

International audience; We report evidence that 29-month-old toddlers and 10-month-old preverbal infants discriminate between two agents: a pro-social agent, who performs a positive (comforting) action on a human patient and a negative (harmful) action on an inanimate object, and an anti-social agent, who does the converse. The evidence shows that they prefer the former to the latter even though the agents perform the same bodily movements. Given that humans can cause physical harm to their conspecifics, we discuss this finding in light of the likely adaptive value of the ability to detect harmful human agents.

Summary Prospecting allows individuals to gather information on the local quality of potential future breeding sites. In a variable and heterogeneous environment, it plays a major role in breeding habitat selection and potentially helps individuals make optimal dispersal decisions. Although prospecting movements, involving visits to other breeding sites, have been observed in many species at relatively fine spatial scales, little is known about their occurrence at larger scales. Furthermore, the adaptive value of dispersal strategies in response to environmental changes remains poorly investigated. Here, our main objective is to highlight in what ways tracking devices could constitute powerful tools to study prospecting behaviour at various spatial scales. First, we stress the importance of considering prospecting movements involved in breeding habitat selection and we detail the type of data that can be collected. Then, we review the advantages and constraints associated with the use of tracking devices in this context, and we suggest new perspectives to investigate the behavioural strategies adopted by individuals during breeding habitat selection processes and dispersal decisions. The rapid development of new powerful electronic tools for tracking individual behaviour thus opens a wide range of opportunities. More specifically, it may allow a more thorough understanding of the role of scale-dependent dispersal behaviour in population responses to environmental changes.

Multimale–multifemale primate groups are ideal models to study the impact of kinship on the evolution of sociality. Indeed, the frequent combination of female philopatry and male reproductive skew produces social systems where both maternal and paternal kin are co-resident. Several primates are known to bias their behavior toward both maternal and paternal kin. Moreover, allocation of affiliation toward paternal kin has been shown to depend on the availability in maternal kin: Female baboons invest more in paternal kin after the loss of preferred maternal kin. Here, we examined how affiliation co-varies across kin classes in juvenile mandrills (Mandrillus sphinx), an Old World primate living in a multimale–multifemale society. While affiliation levels observed with the mother and with maternal half-sibs co-varied positively, especially in young females, we found that levels of affiliation among paternal half-sibs correlated negatively with levels of affiliation among individuals from the same matriline (distant kin), possibly as a result of kin availability. In addition, in social species, social bonds between individuals have been linked to differentiated fitness consequences: More socially integrated individuals generally enjoy higher fitness. We therefore also tested whether affiliation during early life impacts fitness. We showed that the global amount of affiliation during juvenescence translated into possible reproductive benefits: Females who were more socially integrated gave birth on average a year before females that were less socially integrated. However, age at first reproduction was not predicted by the amount of affiliation exchanged with any particular kin class. These results add to the growing body of evidence demonstrating differential investment in bonding and possible social adjustments among different kin categories and emphasizing once more the adaptive value of sociality.

International audience; Analogical reasoning is considered the hallmark of human reasoning, but some studies have demonstrated that language-and symbol-trained chimpanzees can also reason analogically. Despite the potential adaptive value of this ability, evidence from other studies strongly suggests that other nonhuman primates do not have this capacity for analogical reasoning. In our three experiments, 6 of 29 baboons acquired the ability to perform a relational matching-to-sample (RMTS) task in which pairs of shapes composed relational displays. Five of these 6 monkeys then transferred this ability to RMTS tasks using novel exemplars of identity (elements in a pair are the same) and nonidentity (elements in a pair are different) relations. This transfer occurred even on trials in which the incorrect pair shared an element with the sample pair with which it was being compared. The baboons retained this ability 12 months later. The findings from our study of symbol-naive monkeys indicate that although language and symbol training facilitate conceptual thinking in nonhuman primates, such training is not a prerequisite for analogical reasoning.

International audience; Introduction Relationships between wood density and hydraulic efficiency and safety (hydraulic specific conductivity and vulnerability to cavitation, respectively) could clarify the physiological process explaining the impact of density on fitness. We have used new, relatively high-throughput phenotyping methods to estimate genetic variation of wood hydraulic specific conductivity (k (s)) and vulnerability to cavitation (VC) as an important step toward demonstrating the adaptive value of wood density. Objective The first aim of this study is to test if, in Douglas-fir, there is a relationship between wood hydraulic properties (k (s) and VC) and wood density. The second objective is to estimate genetic variation of wood k (s) and VC. These results could aid understanding of the role of wood density in the hydraulic properties of xylem and may clarify the role of wood density in adaptation to drought. Results Many significant relationships were found between wood density and wood hydraulic properties at clone and tree level, as well as significant genetic variation for k (s) and VC. We have also found positive correlations between tree height, specific conductivity and vulnerability to cavitation, but no relation was found between radial growth and hydraulic variables. Conclusions Our results suggest that wood density has an adaptive value and that microdensity can be used to study adaptation to drought in Douglas-fir. The novel methods used to measure k (s) and VC proved to be interesting alternatives for localized measurement of wood hydraulic properties and were compatible with a robust estimation of genetic variation.

International audience; Individual decision-making and behavioral plasticity, and hence reproductive success, depend on nutritional state. Despite the importance of food for lifehistory functions, when and how often parasitoids encounter and consume food in natural settings remain largely unknown. In this study, we aimed at determining the food intake history of the Venturia canescens parasitoids in field conditions. To fulfill this objective, we compared the nutritional state of lab individuals of known feeding history and of field-released individuals allowed to freely forage under natural conditions. Nutritional state and feeding history were determined by using a combination of physiological parameters based on sugar assays. Field-released wasps were caught during periods starting either 5 or 24 h after release. Our results show that in the field, the wasps search actively for carbohydrate food sources. Our work also indicates that feeding activity of wasps in the field can be better understood by using the combination of key physiological parameters. The adaptive value of the feeding pattern and the relevance of the approach used are discussed.

International audience; Vocal structure should reflect vocal function. While much attention has focused on quantifying attributes of harmonic vocalizations, the vocalizations of many species also may contain non-linear phenomena such as warbles, subharmonics, biphonation, and deterministic chaos or noise. The function of these non-linearities remains enigmatic. In some species, harmonic vocalizations abruptly become ‘noisy’ when individuals are physiologically aroused and the sudden onset of these non-linearities could signal arousal or fear to receivers. One untested functional hypothesis is that vocalizations containing non-linearities are more variable from one rendition to the next, and thus are harder to habituate to. In some situations, reducing the likelihood of habituation could be important. Signals that are highly evocative are more difficult to habituate to. Thus, we conducted playback experiments to foraging yellow-bellied marmots (Marmota flaviventris) to determine whether the addition of white noise (a non-linear acoustic phenomenon) to alarm calls elicited a greater response than control calls without the non-linearity or control calls with silence, rather than noise, added to them. Marmots spent less time foraging after hearing calls that included noise than after normal or control calls. This result is consistent with the unpredictability hypothesis and suggests that the adaptive value of non-linearities is to prevent habituation.

International audience; Infections are often followed by a change in body odours. For a long time, these changes were considered as non-specific (with no adaptive value) but recent evidences suggest that this may not always be true. Odour modifications due to an infection may either be of adaptive value for the parasite or the host. Here, we describe the observations in support of this idea, discuss the potential roles these modifications may play for the parasite and the host and propose a set of future directions that we think should allow to better understand the mechanisms at the origin of these modifications and how they may be used by both parasites and their human hosts.

International audience; High corticosterone levels can have deleterious effects in developing avian embryos and chicks. Therefore, it may be adaptive for avian mothers to reduce corticosterone transfer to their eggs. However, until now, data about the active or/and passive role of mothers in corticosterone transfer to eggs are inconclusive. Here, we study maternal investment into A- and B-eggs of southern rockhopper penguins (Eudyptes chrysocome chrysocome). This species exhibits reversed hatching asynchrony and provides a unique model to test whether there is a strategic investment in corticosterone favoring the B-chick, which is most likely to survive. We found that rockhopper penguins had the highest yolk concentrations of any wild bird species studied so far. Contrary to our expectations, B-eggs had more yolk corticosterone both in concentration and in quantity than A-eggs, independently of the laying period and the level of human disturbance. Additionally, females deposited more yolk corticosterone in their eggs when they were disturbed. However, this disturbance effect was particularly strong for A-eggs and for late-laid eggs. The present data support neither the predictions for an active regulation nor for a passive deposition, and hormone deposition mechanisms still need to be explored. The adaptive value, if any, of high yolk corticosterone is presently unknown.

International audience; The daily hatching rhythm of Rhodnius prolixus eggs is established under an LD 12 : 12 h photoperiod. The endogenous nature of this rhythm is demonstrated under continuous darkness. Hatching takes place during the last half of the night, when the maximum environmental relative humidity (RH) and minimum temperature (i.e. the combination that yields the lower water vapour saturation deficits) occur in wild habitats. This temporal window of approximately 7 h recurs at 24-h intervals, producing a hatching rhythm in the population. The effects of the RH upon egg-hatching are analysed. In agreement with previous studies, hatching success is strongly affected by environmental RH. Although 88% of eggs hatch at 75% RH, only 4% and 10% hatch at 0% or 100% RH, respectively. These results support the hypothesis that temporal synchronization is related to the avoidance of low environmental RHs, high environmental temperatures, or high water vapour saturation deficit during hatching, thus minimizing their deleterious effects. Given that eggs cannot choose optimum microclimatic conditions, selective pressures appear to have originated from an adaptive temporal rather than spatial hygropreference.

International audience; Fundamental plant traits such as support, anchorage, and protection against environmental stress depend substantially on biomechanical design. The costs, subsequent trade-offs, and effects on plant performance of mechanical traits are not well understood, but it appears that many of these traits have evolved in response to abiotic and biotic mechanical forces and resource deficits. The relationships between environmental stresses and mechanical traits can be specific and direct, as in responses to strong winds, with structural reinforcement related to plant survival. Some traits such as leaf toughness might provide protection from multiple forms of stress. In both cases, the adaptive value of mechanical traits may vary between habitats, so is best considered in the context of the broader growth environment, not just of the proximate stress. Plants can also show considerable phenotypic plasticity in mechanical traits, allowing adjustment to changing environments across a range of spatial and temporal scales. However, it is not always clear whether a mechanical property is adaptive or a consequence of the physiology associated with stress. Mechanical traits do not only affect plant survival; evidence suggests they have downstream effects on ecosystem organization and functioning (e.g., diversity, trophic relationships, and productivity), but these remain poorly explored.

International audience; Host acceptance decision in parasitic wasps strongly depends on the parasitism status of the encountered host. In solitary species, a host only allows the development of a single parasitic larva and then, any oviposition in an already parasitised host leads to larval competition and loss of offspring. Females of many parasitoid species are able to discriminate between parasitised hosts and healthy ones. However, the host discrimination process may require more time than oviposition, exposing the wasp to high risks when the host has efficient defences. Consequently, depending on the degree of success of the host defence, the cost of host inspection for discrimination can outweigh the benefit of superparasitism avoidance. In the present paper, a theoretical approach was developed for determining how host defences may affect optimal host acceptance behaviour in parasitoids. The present model compares the lifetime reproductive success over the strategy used, discrimination and n! o-discrimination: a discriminating wasp sets a relatively greater value in its current oviposition, while a non-discriminating female sets a greater value in its own survival and future reproduction. The model predicts that depending on physiological state variables and environmental state variables, the optimal policy is not discriminating. Our results suggest that the low discriminating ability observed in some parasitic wasps could probably be an evolutionary response to host defences pressure

Coprophagy occurred during major periods of feeding on fruits of Dialium spp. (Caesalpiniaceae) in a group of orphaned chimpanzees released in Conkouati Douli National Park, Republic of Congo. Since stress, boredom or food scarcity could not explain coprophagy according to our daily behavioral and veterinary control observations, we suggest that Dialium seeds were the item of interest in the feces. Two types of Dialium seeds were commonly found in the feces after chimpanzees swallowed the mesocarp and whole seeds together. These seeds were either whole and hard or whole/broken and soft imbibed. A mechanical and/or chemical effect of the gut passage may enable the chimpanzees to chew and ingest the seeds, thus providing nutritional intake.

A copepod in a seasonal environment continuously faces the trade-offs among allocating surplus growth to a storage compartment (lipids), to somatic growth or to reproduction. By building up lipids, it can survive periods with low food, and gain reproductive success the following season by transforming fat to eggs. Also, copepods face a trade-off between survival and growth, as surface waters generally are more risky and productive than the dark refuges at greater depths, both in the diel and annual temporal scale. Implicit in these trade-offs are the numbers of generations, population dynamics and productive potential of the copepod. The authors develop a model which is used to investigate (1) how optimal diel arid ontogenetic vertical migration might vary with season, individual state (size and lipid reserves) and growth conditions; (2) whether fat is mainly used for overwintering or for fueling reproduction in early spring; and (3) the adaptive value of behavioural flexibility in migration patt...