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Animals of many species lay their eggs in nests built to provide their offspring a suitable microhabitat during a critical phase of development. Nest characteristics result from two processes: habitat choice and modification that may impact differently nest suitability for eggs. This field-based study aimed to estimate their independent effects and their interaction effects on the capacity of sea lamprey nests to retain eggs. Physical variables linked to both habitat choice and habitat modification affected nest suitability, but higher effect sizes indicated the prevalence of habitat modification. The most retentive nests were built in habitats with slower current (habitat choice) and had steeper slope between the deepest part of the nest (pit) and the downstream mound (habitat modification); the positive effect of the steep slope increasing with flow velocity in the nest. Our results show that habitat choice and habitat modification must be taken into account in evolutionary or conservation studies that analyze nest-building animals.

Population estimation implies considering the biology of the species, but also the constraints of logistic aspects such as cost. While common methods based on individual counts can provide precise estimates, they require an extensive sampling effort. An alternative to these methods is using cues linked to the species abundance. In that case, producing absolute estimates requires assessing the relationship between the individuals and these cues. In this paper, we propose a model based on data on spawning behaviour and Approximate Bayesian Computation to estimate the number of sea lamprey spawners using nest counts data. By counting the daily number of occupied nests and using parameters from a behavioural study, we set up a model simulating a spawning season and returning a population estimate by comparison with field data. Our model gives realistic estimates and we discuss the parameters on which to prioritize data collection with a sensitivity analysis, and show that halving the sample size provides a still satisfactory accuracy. We made an easily parametrizable application to run the model for any people interested in sea lamprey population estimation, and believe this framework to be a good way to increase data collection for both endangered and invasive sea lamprey. Functioning was funded by Pôle Gestion des Migrateurs Amphihalins dans leur Environnement. M.D. PhD is financed by Univ. Pau & Pays Adour and UPV/EHU.

Egg drift from the nest is clearly an important cause of mortality in lithophilic species, but the effect of substrate composition on this process has been overlooked. Here, we investigated the role of substrate on the spawning preference and egg retention of river lamprey (Lampetra fluviatilis) during a whole breeding season in a two-option experimental setting. Despite no initial preference, the lamprey eventually favoured the most efficient substrate for egg retention. The pebbly substrate hosted 12 times as many matings as the sandy one, while blurting 20% fewer eggs.

Unrelated males sometimes share their nests and their mates, an example of male-male cooperation that calls for an evolutionary explanation. We developed a game-theoretic model of this situation under the assumption that males could be either "aggressors," attempting to drive off any other arriving male, or "tolerators," willing to share a nest and mates with another tolerator male. We modeled nest dynamics by changing the frequency of the two types in the population and determined how this affected their fitness. We use the sea lamprey as a case study to generate a plausible array of behavioral traits and ecological conditions for the model. Under these conditions, only aggressors or only tolerators could persist, not both, but we also show how exceptions can arise. Aggressors predominated for the standard conditions we chose, but tolerators could take over when females favored them through nest choice or increased mating rate. High nesting densities and high fighting costs also tended to favor tolerators. At moderate to low densities of individuals in the nesting area, female behavior, based on their own costs and benefits, should determine the outcome.

International audience; Besides egg fertilization, females of many taxa obtain direct fitness benefits from male mates, such as food, protection or paternal care. But males often increase their own fitness by mating with several females, among which they distribute sperm along with the above-mentioned benefits, reducing the benefits to individual females. These diverging interests lead to a conflict in which each female may try to ensure male fidelity and get exclusive access to male-provided benefits. Here, we use a theoretical model to show how a female of an externally fertilizing species may achieve mate fidelity by soliciting copulations at such a rate that the male has insufficient sperm left to increase his fitness with additional females. We show that three alternative condition-dependent evolutionarily stable mating relationships emerge in this scenario, based on whether one mate’s preference for mating rate dominates, or the conflict is resolved by what amounts to negotiation. We demonstrate how these outcomes depend on some features of physiology, ecology, and behavior. In particular, a greater reproductive benefit to a female from exclusive access to a male partner—or the occasional tendency of females to withhold eggs during mating—can increase male fidelity; and continuous sperm regeneration rather than an initially-set stock of sperm allows for multiple within-pair mating across all three mating pattern

During the reproductive season, animals have to manage both their energetic budget and gamete stock. In particular, for semelparous capital breeders with determinate fecundity and no parental care other than gametic investment, the depletion of energetic stock must match the depletion of gametic stock, so that individuals get exhausted just after their last egg is laid and fertilized. Although these budgets are managed continuously, monitoring the dynamics of mating acts and energy expenditure at a fine temporal scale in the wild is challenging.This study aimed to quantify the individual dynamics of spawning acts and the concomitant energy expenditure of female Allis shad (Alosa alosa) throughout their mating season.Using eight individual-borne accelerometers for one month, we collected tri-axial acceleration, temperature, and pressure data that we analysed to i) detect the timing of spawning acts, ii) estimate energy expenditure from tail beat frequency and water temperature, and iii) monitor changes in body roundness from the position of the dorsally-mounted tag relative to the vertical plane.Female shad had a higher probability to spawn during warmer nights, and their spawning acts were synchronized (both individually and inter-individually) within each active night. They experienced warmer temperature, remained deeper, swan more slowly and spent less energy during daytime than night time. Over one month of spawning, they performed on average 15.75 spawning acts, spent on average 6 277 kJ and died with a significant portion of residual oocytes. The acceleration-based indicator of body roundness was correlated to condition coefficient measured at capture, and globally decreased through the spawning season, although the indicator was noisy and was not correlated to changes in estimated energy expenditure.Despite significant individual variability, our results indicate that female shad exhausted their energetic stock faster than their egg stock. Water warming will increase the rate of energy expenditure, which might increase the risk that shad die with a large stock of unspent eggs. Although perfectible, the three complementary analyses of acceleration data are promising for in situ monitoring of energy expenditure related to specific behaviour.

Nest building relates to reproductive effort, sexual selection, intersexual conflict and cooperation and may be linked to individual phenotype and interindividual interactions. In particular, larger individuals having more energy reserves are expected to build more, larger nests, without having to trade intrasexual competition for cooperative nest building. Capture-mark-recapture and nest survey of sea lamprey (Petromyzon marinus L. 1758) were combined to assess the relationship between individuals and nesting activity on a spawning ground, throughout a breeding season, during which 202 nests were observed and 114 individuals were captured. On average, males and females stayed 8.33 ± 1.02 and 3.57 ± 1.04 days on the spawning ground, visited 2.26 ± 1.72 and 1.67 ± 1.17 nests and encountered 2.33 ± 2.13 mates for males and 2.29 ± 1.32 mates for females, respectively, and the number of mates encountered increased with the number of nests visited. Body size had no effect on the duration of presence on spawning ground, number of nests visited, number of individuals per nest and sex ratio on nest or nest volume. Bigger nests were found at the end of the season and were not necessarily built by more individuals. This work brings insights on the mating system and cooperative nest building in sea lamprey and may inform managers who want to estimate sea lamprey populations via nest surveys.

This study assesses whether the effective number of breeders (Nb ) can be estimated using a time and cost-effective protocol using genetic sibship reconstruction from a single sample of young-of-the-year (YOY) for the purposes of Atlantic salmon Salmo salar population monitoring. Nb was estimated for 10 consecutive reproductive seasons for S. salar in the River Nivelle, a small population located at the rear-edge of the species distribution area in France, chronically under its conservation limit and subjected to anthropogenic and environmental changes. Subsampling of real and simulated data showed that accurate estimates of Nb can be obtained from YOY genotypes, collected at moderate random sampling intensity, achievable using routine juvenile electrofishing protocols. Spatial bias and time elapsed since spawning were found to affect estimates, which must be accounted for in sampling designs. Nb estimated in autumn for S. salar in the River Nivelle was low and variable across years from 23 (95% C.I. 14-41) to 75 (53-101) and was not statistically correlated with the estimated number of returning adults, but it was positively correlated with the estimated number of YOY at age 9 months. Nb was found to be lower for intermediate levels of redd aggregation, suggesting that the strength of the competition between males to access females affects reproductive success variance depending on redd spatial configuration. Thus, environmental factors such as habitat availability and quality for spawning and YOY development predominate over demographic ones (number of returning adults) in driving long-term population viability for S. salar in the River Nivelle. This study showcases Nb as an integrated parameter, encompassing demographic and ecological information about a reproductive event, relevant to the assessment of both short-term effects of management practices and long-term population conservation status.

International audience; We assessed the effects of sexual maturity on space use in Atlantic salmon (Salmo salar) parr as facultative early maturation enables us to work on individuals belonging to the same cohort. We monitored the space use of 40 1-year-old males in natura throughout a breeding season. First, mature individuals covered longer distances (absolute and upstream) and located within broader home ranges than immature parr. Second, sexual maturity also generated a higher interindividual variability in space use. Finally, mature individuals exhibited a higher probability of association with likely breeding sites on average. However, some mature individuals experienced a lower probability than immature individuals, suggesting that the space use of some mature individuals may not be optimal. Moreover, mature parr exploiting a broader home range or covering longer upstream distances had a higher probability of association with likely breeding sites. Covering longer upstream distances may therefore increase the reproductive success of mature parr, while involving higher energetic costs and a greater risk of predation

This study aimed to test mate choice and selection during early life stages on major histocompatibility (MH) genotype in natural families of Atlantic salmon Salmo salar spawners and juveniles, using nine microsatellites to reconstruct families, one microsatellite linked to an MH class I gene and one minisatellite linked to an MH class II gene. MH-based mate choice was only detected for the class I locus on the first year, with lower expected heterozygosity in the offspring of actually mated pairs than predicted under random mating. The genotype frequencies of MH-linked loci observed in the juveniles were compared with frequencies expected from Mendelian inheritance of parental alleles to detect selection during early life stages. No selection was detected on the locus linked to class I gene. For the locus linked to class II gene, observed heterozygosity was higher than expected in the first year and lower in the second year, suggesting overdominance and underdominance, respectively. Within family, juveniles' body size was linked to heterozygosity at the same locus, with longer heterozygotes in the first year and longer homozygotes in the second year. Selection therefore seems to differ from one locus to the other and from year to year.

International audience; Individual interactions are crucial to many ecological processes but are difficult to quantify for long periods in aquatic animals. In this study, we applied a digital proximity logging device recently developed for terrestrial animals to a freshwater fish, the brown trout (Salmo trutta L.). After preliminary calibration and quantification of detection errors, we recorded the interactions occurring between five male and four female brown trout in an artificial channel during one week of the spawning season. The 55,637 logs recorded allowed us to describe the encounter network and its fine scale evolution. In particular, the time spent with females varied a lot across males, from two to 24 h in a five-day period, and the males, which spent the most time with females tended to mate more. At the individual level, the temporal distribution of encounters reflected shifts in dominance status, with males sequentially taking over exclusive proximity with females before spawning. Beyond sexual encounters, the method presented here could be applied to many processes interesting to fish ecologists, such as predator-prey interactions, intra and interspecific competition or disease transmission

International audience; Salmonid females invest heavily in reproduction, through gamete production, habitat selection and maternal care. Habitat selection and maternal care are expected to provide shelter for eggs against scouring and predators. However, females also tend to produce variable egg sizes, and this trait may interact with habitat quality to influence the survival of offspring. In this study, we aimed at evaluating the role of female habitat selection on egg survival conditional on individual egg size and female body size. We monitored female reproductive activity in two natural rivers for 3 years, in order to relate nest characteristics to female body size. Bigger females dug deeper nests at lower shear stress force. Right after the end of nest construction, we sampled a part of the eggs laid by each female, measured them individually, and placed them back using capsules within their original position in the nest. At time of hatching, the capsules within the nest were collected and individual egg mortality was assessed. Our results indicate that scouring was the main driver for mortality (75%) and that nest burial depth and shear stress force above the nest both influenced scouring. However, subsequent survival was influenced by neither nest characteristics, individual egg size, nor the interaction between both. It is therefore expected that traits or tactics that reduce nest scouring probability should be under strong selection

International audience; Spatial aggregation within a population is a widespread phenomenon which may both exacerbate local competition and the stochastic effect of local environmental perturbations. In particular, the spatial aggregation of nests may strongly affect recruitment and hence population dynamics. Although the negative effect of local density on local recruitment has often been theoretically extended to population dynamics, very few studies have demonstrated the effect of local aggregation on the whole population recruitment. Using a long-term survey of a small Atlantic salmon population, we tested the effect of spatial aggregation on the whole population recruitment and whether accounting for population stock is important or not when explaining the population recruitment. We found that accounting for population stock is necessary and that spatial aggregation of nests improved estimates of population recruitment. The spatial aggregation of nests did not impact the average population recruitment; however, a stronger aggregationdiminished the variability of population recruitment. Our findings suggest that the aggregation of nests among some breeding areas does not necessarily impair the whole population recruitment and significantly reduces the stochasticity of the recruitment. In addition, the aggregation of nests seems to be the result of an ideal distribution of females, selecting the best-breeding sites. Our results also indicate that females select breeding sites on environmental risk to spawn within the safest sites. This study warns against the extrapolation of local density dependence observations to the population level, and advocates for investigating the effect of aggregation on the demographic and evolutionary population dynamics, a clear contribution of aggregation on population dynamic processes being found in the Nivelle population.

International audience; Melanins are the most widespread pigments in animals but their adaptive significance remains elusive. Recent studies suggest that intraspecific variation in melanin-based coloration reflects individual genetic-based alternative strategies to cope with environment variability, which could be crucial for their responses to climate changes. However, empirical evidence is still scarce. In this study, we tested how skin coloration in natural populations of brown trout Salmo trutta fario would reflect alternative reproductive strategies in different environments. We experimentally manipulated the flow regime (constant vs. variable) in artificial streams and compared the reproductive investment (body mass and plasma triglyceride variations), innate immunity (variations in plasma peroxidase and lysozyme activity) and reproductive success (number of mates and offspring) of differently colored brown trout over 2 reproductive seasons. Results show that darker males had a higher reproductive investment, but similar immune variations during reproduction compared to paler males. In addition, this reproductive investment was higher in variable environments. However, this did not translate into a higher reproductive success in variable environments, as darker males had a similar number of mates and offspring compared to their paler counterparts under a variable water flow. Since climate change will likely lead to an increased flow variability in the next decades, this suggests that darker brown trout could incur a higher energetic cost of reproduction and could be more impacted by climate changes than their paler counterparts. This highlights the need to take into account intraspecific variability to better forecast the response of natural populations to climate changes.

International audience; Methodologies enabling the monitoring of animal movement and behavior in 3-dimensions (3D; x, y, z, the latter accounting for the vertical dimension) are becoming increasingly accessible and can be deployed on entire groups of animals inhabiting 3D habitats. When 2-dimensional (2D; x, y) space-use analyses are used on such groups, their spatial organization is represented as a planar projection of individuals’ space-use. Movement on the vertical dimension is ignored and could biased ecological inference made from the spatial structure of the group. We used a digital imaging technique to track movements and feeding behavior of individual animals within a free-range aggregation of juvenile drift-feeding fish (Galaxias anomalus) in 3D and at fine spatiotemporal scales. We estimated spatiotemporal overlap of space-use and feeding territories between group-members using 2D (x, y) and 3D spatial analysis to: (1) describe the spatial structure of the group, (2) identify patterns of resource partitioning, and (3) investigate the relationship between space-use overlap and feeding behavior. We found that overlapping ratios of space-use and feeding territories were over-estimated in 2D, while 3D analysis of space-use provided evidence of spatial partitioning between group-members. We also found that, regardless of the computation used, the overlapping ratios of space-use were positively correlated with overlapping ratios of feeding territories while no effect was found on feeding activity. In conclusion, whilst 3D analysis provided valuable information on the spatial structure of a group, inferences on the ecological function of space-use can also be obtained from 2D analysis

The evolution of parental care depends on the sex-dependent resolution of a trade-off between present and future reproduction. In salmonids, the mating systems are often characterised by fierce male-male competition, and the absence of paternal care is widely admitted in these species. However, the fact that brown trout eggs can be cannibalised by peripheral individuals just after spawning suggests that dominant males would benefit from protecting their offspring by keeping cannibals away from the nest. We used 77 field observations of brown trout spawning to document the defensive behaviour of dominant males towards peripheral individuals before and after spawning, and test whether this behaviour was related to the probability of the clutch being cannibalised. We showed that dominant males stayed on the nest and chased peripherals even after the eggs were laid and fertilised. The number of chases performed by dominant males during the 2 min following spawning was negatively correlated to the probability of egg cannibalism. This result indicates that brown trout males can provide direct benefits to females through protection against egg cannibalism by peripheral individuals.

– Programmes of habitat restoration usually assume that the targeted populations will readily colonise the newly provided habitat. However, this assumption may not always hold, and the success of restoration may be impaired if the individuals are driven to aggregate in areas of the habitat already available instead of spreading to new ones. We investigated how weirs situated along a river could drive Atlantic salmon (Salmo salar) to aggregate their redds and tested whether aggregation intensified at low fish density. For this, we applied spatial point pattern analysis to a data set consisting on the distribution of salmon redds in a small river over 15 years (1992–2006). Within the habitat suitable for spawning, redds were significantly aggregated, especially in the first 15 morphodynamic units below weirs. Our results suggest that the constraint imposed by obstacles on redd distribution should be considered when conducting habitat restoration.

Habitat selection by dispersers is the focus of much theoretical models, most of which are based on the assumption of negative density dependence. The archetype of these models is the ideal free distribution, characterized by an evolutionary stable state where more competitors aggregate in better habitats, so that the fitness benefit of resource abundance is equally offset by the cost of competition in all habitats. In this study, we used parentage analysis on microsatellite genotypes to test the ideal free distribution in a natural population of aphid parasitoids. Parentage analysis was conducted on parasitoids emerging from aphid colonies. We inferred the number of foundress females which had reproduced in each colony, as well as the number of offspring for each foundress. As predicted by the ideal free distribution, the number of offspring per foundress per colony did not depend on the number of hosts per colony. However, contrary to ideal free distribution predictions, it was affected by the number of foundresses per colony. In surprising contrast with the basic assumption of negative density dependence, individual fitness increased with the number of foundresses. Moreover, parentage analysis revealed a very low number of offspring per foundress per colony (mean = 1.8). This observed distribution questions the validity of classical models of habitat choice based on competition. Indeed, our results provide a new illustration reinforcing a growing body of theory and data on positive density dependence. Our results also suggest that the avoidance of hyperparasitism and predation, although generally neglected, may shape the distribution of parasitoids in the field.

International audience; We combined habitat mapping, radio tracking of adults, redd mapping, and genetic parentage analysis on juveniles for 2 consecutive years to test eight predictions on the reproductive payoffs and individual features associated with space use tactics of anadromous Atlantic salmon (Salmo salar) in a natural population. Regarding payoffs, we found that (1) males settled in better habitat, visited more redds, and tended to get more mates than males settled in poorer habitat; (2) they also sired more offspring; (3) the latter effect was stronger in the first year, when redds were more aggregated; and (4) female reproductive success increased with habitat quality in their home range, especially in the first year. For individual features, (5) individuals that settled earlier in their home range had better habitat for juvenile production, but only in the first year; (6) females were less mobile than males, especially in the second year; (7) larger males did not settle in better habitats than smaller males; and (8) smaller males were not more mobile than larger males.

Ajouter pagination et wos; International audience; Assortative mating is thought to play a key role in reproductive isolation. However, most experimental studies of assortative mating do not take place in multiple natural environments, and hence, they ignore its potential context dependence. We implemented an experiment in which two populations of brown trout (Salmo trutta) with different natural flow regimes were placed into semi-natural stream channels under two different artificial flow regimes. Natural reproduction was allowed, and reproductive isolation was measured by means of parentage assignment to compare within-population vs. between-population male–female mating and relative offspring production. For both metrics, reproductive isolation was highly context dependent: no isolation was evident under one flow regime, but strong isolation was evident under the other flow regime. These patterns were fully driven by variance in the mating success of males from one of the two populations. Our results highlight how reproductive isolation through assortative mating can be strongly context dependent, which could have dramatic consequences for patterns of gene flow and speciation under environmental change.

International audience; The precocious maturation of some male Atlantic salmon (Salmo salar L.) has become a textbook example of alternative mating tactics, but the only estimates of reproductive success available so far are either the collective contribution of precocious males to reproduction in the wild or individual reproductive success in oversimplified experimental conditions. Using genetic parentage analysis on anadromous and precocious potential spawners and their offspring, we quantified components of individual reproductive success of both tactics in a natural population. On average, precocious males produced 2.24 (variance 67.62) offspring, against 27.17 (3080) for anadromous males. For both tactics, most of the variance in reproductive success was due to mating success, with 83 % of precocious males having no mate, against 50 % for anadromous males. Body size increased reproductive success of anadromous males and tended to decrease precocious males’ reproductive success. Although these results do not solve the coexistence of alternative reproductive tactics (ARTs) in Atlantic salmon, their inclusion in comprehensive models of lifetime reproductive success should shed light on the evolution of precocious maturation in Atlantic salmon and its effect on the selection of phenotypic traits.

International audience; Environmental stochasticity is expected to shape life histories of species, wherein organisms subjected to strong environmental variation should display adaptive response by being able to tune their reproductive investment. For riverine ecosystems, climate models forecast an increase in the frequency and intensity of extreme events such as floods and droughts. The speed and the mechanisms by which organisms may adapt their reproductive investment are therefore of primary importance to understand how species will cope with such radical environmental changes. In the present study, we sampled spawners fromtwo different populations of wild brown trout, originating from two environments with contrasting levels of flow stochasticity. We placed them in sympatry within an experimental channel during reproductive season. In one modality, water flow was maintained constant, whereas in another modality, water flow was highly variable. Reproductive investment of all individuals was monitored usingweight and energetic plasma metabolite variation throughout the reproductive season. Only the populations originating fromthe most variable environment showed a plastic response to experimental manipulation of water flow, the females being able to reduce their weight variation (from 19.2% to 13.1%) and metabolites variations (from 84.2% to 18.6% for triglycerides for instance) under variable flow conditions. These results imply that mechanisms to cope with environmental stochasticity can differ between populations of the same species, where some populations can be plastic whereas other cannot

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Animals foraging for patchily distributed resources may optimize their foraging decisions concerning the patches they encounter, provided that they base these decisions on reliable information about the profitability of the habitat as a whole. Females of the parasitoid Lysiphlebus testaceipes exploit aphid hosts, which typically aggregate in discrete colonies. We show here how betweencolony travel time and the number of aphids in previously visited colonies affect parasitoid foraging behavior. We first assumed that parasitoids use travel time and previous colony size to estimate a mean rate of fitness gain in the habitat and derived quantitative predictions concerning the effect of these two variables on patch residence time and patch-leaving rate of attack. We then tested these theoretical predictions in laboratory experiments in which female parasitoids were allowed to visit two successive colonies. As predicted, the observed residence time in the second colony increased with increasing travel time and decreasing size of the first colony. Patch-leaving rate of attack decreased with increasing travel time but was not affected by previous colony size. These results suggest that parasitoids use these two variables to assess habitat quality. However, discrepancies between the data obtained and quantitative predictions show that the effect of travel time on patch use may be more complex than assumed in our model. Key words: learning, Lysiphlebus testaceipes, marginal value theorem, optimal foraging theory, patch size, travel time. [Behav Ecol]

International audience; In wild populations, measuring energy invested in the reproduction and disentangling investment in gametes versus investment in reproductive behavior (such as intrasexual competition or intersexual preference) remain challenging.In this study,we investigated the energy expenditure in brown trout reproductive behavior by using two proxies: variation in weight and variation of plasma metabolites involved in energy production, over the course of reproductive season in a semi natural experimental river. We estimated overall reproductive success using genetic assignment at the end of the reproductive season. Results show that triglycerides and free fatty acid concentrations vary negatively during reproduction, while amino-acids and glucose concentrations remain stable.Decrease in triglyceride and free fatty acid concentrations during reproduction is not related to initial con- centration levels or to weight variation. Both metabolite concentration variations and weight variations are correlated to the number of offspring produced, which could indicate that gametic and behavioral reproductive investments substantially contribute to reproductive success in wild brown trout. This study opens a path to further investigate variations in reproductive investment in wild populations

International audience; The emergence of an animal’s personality is the result of interactions between genetics, environment and experience. It is known that individuals are able to modulate their behaviour according to the context or the social environment. Many studies have shown for example, that familiarity among conspecifics diminishes aggressiveness, although little is known about the underlying processes. Nevertheless, personality traits have long been determined while ignoring the social context, especially in lower vertebrates such as fish. In the present experiment, we hypothesize that group connections (network density) may be positively correlated to consistency of aggressiveness by avoiding over-aggressive acts in further encounters. To test this hypothesis, we used eels (Anguilla anguilla) as a model species and monitored both aggressiveness and sociability in 64 individuals over their first 7 months of growth from the glass eel stage. As expected, social fish were less aggressive than their non-social counterparts at all times, highlighting the existence of a behavioural syndrome in eels. Additionally, rank-order consistency of aggressiveness was higher in groups of fish with high social connectivity, compared to those in less-connected fish groups. While aggressiveness must be consistent to be considered a personality trait, our results suggest that both aggressiveness and its consistency are influenced by initial social context

International audience; Microsatellite loci were isolated from the aphid parasitoid Lysiphlebus testaceipes (Hymenoptera: Braconidae). Ten loci were obtained from an enriched partial genomic library. Genetic diversity was analysed at seven of these loci and two natural populations, one on oleander and one on citrus. The observed number of alleles ranged from one to 17, and the observed heterozygosity ranged from 0.37 to 0.82. In both populations, no departure from Hardy-Weinberg equilibrium was detected except for one locus. The differentiation between the two populations was characterized by an F-ST Of 0-09.

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Egg cannibalism is a common behavior among fish taxa and is largely studied in species with parental care. Heterocannibalism and filial cannibalism have both been reported in salmonids, a group with no extended parental care, but the topic remained somewhat under-documented, especially in brown trout (Salmo trutta). In the present study, 83 spawning events were recorded finely with high-resolution video in three natural populations. Redd covering dynamics by females and the timing of cannibalism showed that eggs were vulnerable mainly during the first 120 s after spawning. Cannibalism occurred in 25% of spawnings and was principally perpetrated by peripherals but the sires also cannibalized their brood, especially after multiple mating. The probability of cannibalism increased with operational sex ratio but did not correlate with the date in spawning season. Occurrence of cannibalism also differed between populations. Our results suggest that such behavior is frequent and may reduce the fitness of parents. Its evolutionary implications for population ecology should be considered, since it appeared to be controlled by environmental and spatial factors.

Bayesian updating is a form of learning by which individuals can adapt their behaviour to uncertain environments. In the particular situation of optimal foraging in a patchy habitat, animals may estimate the profitability of the patches they encounter to update their estimate of the profitability of the habitat as a whole, and adjust their foraging decisions accordingly. Recent studies have suggested that parasitoid insects may have such abilities, but were based on too few patches for clear conclusions on Bayesian updating. We studied how females of an aphid parasitoid update their estimate of habitat profitability, by recording their behaviour on a series of seven consecutive host patches, each serving both as a potential cue for habitat profitability and as a means to measure the behavioural response to previously collected information. The experiment was designed to test specific predictions based on Bayesian updating with different memory dynamics. The parasitoids clearly perceived the profitability of the patches, but the effect of previous experience on current patch use was different from our predictions. The reinterpretation of previous studies in the light of our results suggests that foraging parasitoids give more weight to early experience.

Habitat selection by dispersers is the focus of much theoretical models, most of which are based on the assumption of negative density dependence. The archetype of these models is the ideal free distribution, characterized by an evolutionary stable state where more competitors aggregate in better habitats, so that the fitness benefit of resource abundance is equally offset by the cost of competition in all habitats. In this study, we used parentage analysis on microsatellite genotypes to test the ideal free distribution in a natural population of aphid parasitoids. Parentage analysis was conducted on parasitoids emerging from aphid colonies. We inferred the number of foundress females which had reproduced in each colony, as well as the number of offspring for each foundress. As predicted by the ideal free distribution, the number of offspring per foundress per colony did not depend on the number of hosts per colony. However, contrary to ideal free distribution predictions, it was affected by the number of foundresses per colony. In surprising contrast with the basic assumption of negative density dependence, individual fitness increased with the number of foundresses. Moreover, parentage analysis revealed a very low number of offspring per foundress per colony (mean = 1.8). This observed distribution questions the validity of classical models of habitat choice based on competition. Indeed, our results provide a new illustration reinforcing a growing body of theory and data on positive density dependence. Our results also suggest that the avoidance of hyperparasitism and predation, although generally neglected, may shape the distribution of parasitoids in the field.

1. Animals usually require information about the current state of their habitat to optimize their behaviour. For this, they can use a learning process through which their estimate is continually updated according to the cues they perceive. Identifying these cues is a long-standing but still inveterate challenge for ecologists. 2. The use of plant cues by aphid parasitoids for the assessment of habitat profitability and the adaptation of patch exploitation was studied. Grounding on predictions from optimal foraging theory, we tested whether parasitoids exploited host patches less intensively after visiting heavily infested plants than after visiting plants bearing fewer aphids. 3. As predicted, after visiting heavily infested plants parasitoids reduced their residence time and attacked fewer hosts in the next patch. This was the case regardless of whether the aphids were actually present on the first plant, indicating that the cue came from the plant. Moreover, the level of infestation of a plant at some distance from the first plant visited affected parasitoid patch exploitation on the second plant in a similar manner, indicating that the cue was volatile. 4. These results highlight a novel role of herbivore-induced volatiles in parasitoid foraging behaviour, different from the widely studied attraction at a distance.

International audience; 1. Optimal foraging models ultimately predict that female parasitoids should exploit rich host patches for longer than poorer ones. At the proximate level, mechanistic models and experimental studies show that parasitoids use both chemicals produced by their hosts and direct encounters with their hosts to estimate patch quality. Although it has been extensively studied in the context of host location, the use of herbivore-induced plant response by insect parasitoids has never been considered in the context of patch time allocation. 2. In this study, the respective roles of herbivore-induced plant response and direct contact with hosts on the foraging behaviour of Lisiphlebus testaceipes females on an aphid patch were quantified. For this, the level of herbivore-induced plant response and the number of aphids on the leaf bearing the patch were manipulated independently. Different levels of plant response were obtained by varying the duration of infestation on another leaf. 3. Parasitoid residence time and number of attacks increased with both the level of plant response and the number of aphids. 4. These results suggest that L. testaceipes females use the combination of herbivore-induced response of plants and direct encounters with hosts to assess patch quality and adjust their patch use behaviour

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Habitat fragmentation and reduction in the availability of suitable habitats are significant threats to ecosystems in particularly for freshwater ones. For instance, accessibility, availability, and quality of breeding sites of Atlantic salmon, \textit{Salmo salar}, can be restricting in some rivers due to human activities and dams. Such threats may affect distribution of potential breeders because after their up-river migration, salmon females distribute within available breeding sites. Spatial distribution of females determines the spatial distribution of breeder males. Dominant males try to monopolise several females, whereas subordinate males adopt a sneaky behaviour. Access to females by males depends on the spatial distribution of females and on males' displacements within a river. The spatial distribution of females generates the spatial distribution of juveniles, aggregating them at some breeding sites. The latter aggregation of juveniles may raise the density-dependent mortality with potential consequences on population dynamics. The thesis aims to assess how space use of potential breeders, namely mature individuals able to spawn or fertilise eggs, influence population dynamics and sexual selection.I combined different approaches and different temporal and spatial scales to potential effects of space use of potential breeders. Time series of stock (deposited eggs) and of recruitment (juveniles) for the salmon population of the Nivelle River were combined with measures of spatial aggregation of nests. The effects of displacements and spatial distribution of potential breeders on their participation in reproduction were tested through inferring the sexual network of the population.I found that spatial aggregation of nests improved the recruitment variability but did not affect the average recruitment. The spatial aggregation of nests resulting from female aggregation was also linked to the number of effective breeders through a U-shaped curve. Such relationships suggested mate monopolization dependent on the spatial aggregation of females. The negative effect of the spatial isolation of females on their number of mates also suggest such mate monopolization. Then, the inferred sexual network enabled me to highlight a local social structure within the population. The latter structure and social competitors impacted the reproductive success of anadromous males. The participation of mature parr was one of the factors diminishing the sexual competition faced by anadromous males. Finally, mature parr were more mobile and moved more upstream than immature parr. Spatial behaviours of mature parr were linked to their participation in reproduction, individuals exhibiting wider home ranges had a higher probability to encounter females.Altogether my results show that space use of potential breeders affect both population dynamics and sexual selection. Then, spatial aggregation of females and of their nests can be beneficial for population dynamics as shown by combining different temporal and spatial scales. Females seemed to aggregate within the best breeding sites with a better environmental stability. The spatial distribution of females affected the ability of males to monopolise several females and participation of sneaky males. The availability of suitable good breeding habitats seemed restricting in the Nivelle, potentially due to the presence of impassable upstream dams. The lack of suitable breeding sites seemed impacting the mating system of the population and the sexual selection operating in. Some management actions to improve the quality of breeding sites and their availability could be planned; La fragmentation des habitats ainsi que la réduction de leur disponibilité sont des menaces importantes pour les écosystèmes, notamment aquatiques. La disponibilité et la qualité des sites de fraie du saumon Atlantique peut donc être limitante dans certaines rivières. Après la migration en rivière, les femelles saumon vont chercher à s'établir dans un des sites de fraie disponibles. La distribution spatiale des femelles va alors influer sur la distribution spatiale des mâles reproducteurs qui vont chercher soit à monopoliser plusieurs femelles (pour les mâles dominants), soit à les approcher en adoptant un comportement "furtif" (pour les mâles satellites). L'accès des mâles aux femelles va donc dépendre de la distribution spatiale des femelles et des déplacements des mâles dans la rivière. La distribution des femelles va également jouer sur la distribution spatiale des juvéniles, les concentrant à certains endroits. Cette concentration peut augmenter la mortalité densité-dépendante qui modifie la dynamique de la population. Cette thèse avait pour but d'évaluer comment l'utilisation de l'espace des potentiels reproducteurs, c'est à dire les individus matures, influence la dynamique de la population et la sélection sexuelle.Des séries temporelles de stock (oeufs déposés) et de recrutement (juvéniles) pour la population de saumon de la Nivelle ont été associées à des mesures de l'agrégation spatiale des nids creusés par les femelles. L'effet des déplacements et de la distribution des reproducteurs sur leur participation à la reproduction a notamment été testé via la reconstruction du réseau d'interactions sexuelles dans la Nivelle.J'ai ainsi démontré que l'agrégation spatiale des nids influa sur la variabilité du recrutement mais pas sur le recrutement moyen. Cette agrégation qui résulte de l'agrégation des femelles a également été liée au nombre de reproducteurs ayant engendrés des juvéniles. Le réseau d'interactions sexuelles a permis de mettre en évidence une structure sociale locale au sein de la population. Cette structure et les compétiteurs présents pouvaient par exemple diminuer le succès reproducteur des mâles. Notamment, les tacons matures qui participent à la reproduction avant de migrer en mer renforçaient la compétition sexuelle dont les mâles dominants faisaient l'objet. Enfin, ces mêmes tacons matures adoptèrent des comportements spatiaux du fait de leur statut de maturité avec des individus bougeant peu et des individus se déplaçant vers l'amont. Ces comportements spatiaux influaient leur participation à la reproduction, l'étendue des domaines de vie et les déplacements vers l'amont augmentaient la probabilité de rencontrer une femelle.Mes résultats m'ont permis de mettre en évidence l'effet de l'utilisation de l'espace des potentiels reproducteurs sur la dynamique de la population et sur la sélection sexuelle. Ainsi, en combinant différentes échelles spatiales et temporelles il a été montré que l'agrégation des femelles pouvait être bénéfique pour la dynamique de la population. Il semble que les femelles tendent à s'agréger d'abord sur les meilleurs sites de fraie avec une plus forte stabilité environnementale. Cette distribution des femelles affecta la capacité des mâles à monopoliser plusieurs femelles, une agrégation modérée permettant une monopolisation. La participation des mâles furtifs anadromes ou tacons matures était également dépendante de l'agrégation des femelles. Il apparait que la disponibilité d'habitats adéquats pour la reproduction semble limitante dans la Nivelle et notamment du fait de la présence de barrages. Ce manque semble affecter le système d'appariement de la population et la sélection sexuelle y opérant. Des mesures visant à améliorer la qualité des sites de fraie déjà disponibles ainsi que leur accessibilité pourraient être envisagées