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International audience; Wild and farmed animals are key elements of natural and managed ecosystems that deliver functions such as pollination, pest control and nutrient cycling within the broader roles they play in contributing to biodiversity and to every category of ecosystem services. They are subjected to global changes with a profound impact on the natural range and viability of animal species, the emergence and spatial distribution of pathogens, land use, ecosystem services and farming sustainability. We urgently need to improve our understanding of how animal populations can respond adaptively and therefore sustainably to these new selective pressures. In this context, we explored the common points between animal production science and animal ecology to identify promising avenues of synergy between communities through the transfer of concepts and/or methodologies, focusing on seven concepts that link both disciplines. Animal adaptability, animal diversity (both within and between species), selection, animal management, animal monitoring, agroecology and viability risks were identified as key concepts that should serve the cross-fertilization of both fields to improve ecosystem resilience and farming sustainability. The need for breaking down interdisciplinary barriers is illustrated by two representative examples: i) the circulation and reassortment of pathogens between wild and domestic animals and ii) the role of animals in nutrient cycles, i.e. recycling nitrogen, phosphorus and carbon through, for example, contribution to soil fertility and carbon sequestration. Our synthesis identifies the need for knowledge integration techniques supported by programmes and policy tools that reverse the fragmentation of animal research toward a unification into a single Animal Research Kinship, OneARK, which sets new objectives for future science policy. At the interface of animal ecology and animal production science, our article promotes an effective application of the agroecology concept to animals and the use of functional diversity to increase resilience in both wild and farmed systems. It also promotes the use of novel monitoring technologies to quantify animal welfare and factors affecting fitness. These measures are needed to evaluate viability risk, predict and potentially increase animal adaptability and improve the management of wild and farmed systems, thereby responding to an increasing demand of society for the development of a sustainable management of systems.

Orthoptera are infected by about 60 species of gregarines assigned to the genus Gregarina Dufour, 1828. Among these species, Gregarina garnhami Canning, 1956 from Schistocerca gregaria (Forsskål, 1775) was considered by Lipa et al. in 1996 to be synonymous with Gregarina acridiorum (Léger 1893), a parasite of several orthopteran species including Locusta migratoria (Linné, 1758). Here, a morphological study and molecular analyses of the SSU rDNA marker demonstrate that specimens of S. gregaria and specimens of L. migratoria are infected by two distinct Gregarina species, G. garnhami and G. acridiorum, respectively. Validation of the species confirms that molecular analyses provide useful taxonomical information. Phenotypic plasticity was clearly observed in the case of G. garnhami: the morphology of its trophozoites, gamonts and syzygies varied according to the geographical location of S. gregaria and the subspecies infected.La taxonomie intégrative confirme que Gregarina garnhami et G. acridiorum (Apicomplexa, Gregarinidae), parasites de Schistocerca gregaria et Locusta migratoria (Insecta, Orthoptera), sont des espèces distinctes.Les orthoptères sont parasités par environ soixante espèces de grégarines affiliées au genre Gregarina Dufour, 1828. Parmi ces espèces Gregarina garnhami Canning, 1956 décrite chez Schistocerca gregaria (Forskål, 1775), a été mise en synonymie par Lipa et al. en 1996 avec Gregarina acridiorum (Léger 1893), parasite de plusieurs espèces d’orthoptères dont Locusta migratoria (Linné, 1758). Ici, une étude morphologique et des analyses moléculaires du marqueur SSU rDNA démontrent que les spécimens de S. gregaria et ceux de L. migratoria sont infectés par 2 espèces distinctes de grégarines, Gregarina garnhami et Gregarina acridiorum, respectivement. La validation de ces espèces confirme l’importance des informations fournies par les analyses moléculaires dans les études taxonomiques. Une plasticité phénotypique a été clairement observée dans le cas de G. garnhami : la morphologie de ses trophozoïtes, gamontes et syzygies varie selon la localisation géographique et la sous-espèce de S. gregaria infectée.

Le criquet pèlerin, Schistocerca gregaria Forskål, 1775, est un ravageur majeur pour l'agriculture. Affiner les connaissances sur sa distribution spatiale est essentiel pour sa gestion préventive. Dans ce but, nous avons utilisé au Tchad une technique de lissage spatial de densités sur 7014 observations du criquet pèlerin (1965-1971 et 1986-2017) afin d'élaborer des cartes saisonnières de répartition pour les périodes d'invasion et de rémission. Trois zones correspondant à des aires de reproduction et foyers de grégarisation ont été identifiées : (1) Kanem/lac Tchad, (2) Batha, (3) Ennedi. La première pourrait être un nouveau foyer de grégarisation. Ces zones se rajoutent à celle du massif du Tibesti, où les signalements sont plus rares que par le passé à cause de l'insécurité. Des prospections plus régulières devraient permettre de confirmer que la distribution du criquet pèlerin a récemment évolué. Mots clés : Schistocerca gregaria / reproduction / prévention des risques / distribution spatiale / plasticité phénotypique Abstract-Mapping of the breeding and gregarization areas of the desert locust in Chad. The desert locust, Schistocerca gregaria Forskål, 1775, is a major threat to agriculture. Refining our knowledge on its spatial distribution is a key point for its preventive management. To do so, we used in Chad a method of spatial smoothing of densities upon 7014 survey points (1965-1971 and 1986-2017) of the desert locust to develop seasonal distribution maps for invasion and remission periods. Three zones corresponding to breeding and gregarization areas have been identified: (1) Kanem/lake Chad, (2) Batha, (3) Ennedi. The first one may be a new gregarization area. These zones add to the Tibesti mountains where locust reports are less frequent than in the past, due to insecurity. More regular surveys should confirm that the distribution of the desert locust has recently changed.

Phenotypic plasticity has been repeatedly suggested to facilitate adaptation to new environmental conditions, as in invasions. Here, we investigate this possibility by focusing on the worldwide invasion of Drosophila suzukii : an invasive species that has rapidly colonized all continents over the last decade. This species is characterized by a highly developed ovipositor, allowing females to lay eggs through the skin of ripe fruits. Using a novel approach based on the combined use of scanning electron microscopy and photogrammetry, we quantified the ovipositor size and three-dimensional shape, contrasting invasive and native populations raised at three different developmental temperatures. We found a small but significant effect of temperature and geographical origin on the ovipositor shape, showing the occurrence of both geographical differentiation and plasticity to temperature. The shape reaction norms are in turn strikingly similar among populations, suggesting very little difference in shape plasticity among invasive and native populations, and therefore rejecting the hypothesis of a particular role for the plasticity of the ovipositor in the invasion success. Overall, the ovipositor shape seems to be a fairly robust trait, indicative of stabilizing selection. The large performance spectrum rather than the flexibility of the ovipositor would thus contribute to the success of D. suzukii worldwide invasion.

[Notes_IRSTEA]revue en libre accès ; lien vers le texte intégral donné dans la notice [Departement_IRSTEA]Territoires [ADD1_IRSTEA]Dynamique et fonctionnement des écosystèmes; International audience; The link between phenotypic plasticity and heterosis is a broad fundamental question, with stakes in breeding. We report a case-study evaluating temporal series of wood ring traits of hybrid larch (Larix decidua x L. kaempferi and reciprocal) in relation to soil water availability. Growth rings record the tree plastic responses to past environmental conditions, and we used random regressions to estimate the reaction norms of ring width and wood density with respect to water availability. We investigated the role of phenotypic plasticity on the construction of hybrid larch heterosis and on the expression of its quantitative genetic parameters. The data came from an intra-/interspecific diallel mating design between both parental species. Progenies were grown in two environmentally contrasted sites, in France. Ring width plasticity with respect to water availability was confirmed, as all three taxa produced narrower rings under the lowest water availability. Hybrid larch appeared to be the most plastic taxon as its superiority over its parental species increased with increasing water availability. Despite the low heritabilities of the investigated traits, we found that the expression of a reliable negative correlation between them was conditional to the water availability environment. Finally, by means of a complementary simulation, we demonstrated that random regression can be applied to model the reaction norms of non-repeated records of phenotypic plasticity bound by a family structure. Random regression is a powerful tool for the modeling of reaction norms in various contexts, especially perennial species.

[Departement_IRSTEA]Eaux [ADD1_IRSTEA]Systèmes aquatiques soumis à des pressions multiples; International audience; Phenotypic plasticity is a ubiquitous process found in all living organisms. Polyphenism is an extreme case of phenotypic plasticity which shares a common scheme in insects such as honeybees, locusts or aphids: an initial perception of environmental stimuli, a neuroendocrine transmission of these signals to the target tissues, the activation of epigenetic mechanisms allowing the setup of alternative transcriptional programs responsible for the establishment of discrete phenotypes. Climate change can modulate the environmental stimuli triggering polyphenisms, and/or some epigenetics marks, thus modifying on the short and long terms the discrete phenotype proportions within populations. This might result in critical ecosystem changes.

Wood density, considered a heritable trait, is often associated with drought tolerance and can be a useful trait for tree breeders to select drought-tolerant provenances. Provenance trials are a useful tool to disentangle genetic variation from plasticity of adaptive traits among populations within the same species. If wood density is a strongly heritable trait selected by climatic conditions, we hypothesize that its variation in provenance trials should be shaped by the provenance climatic variables. To test our hypothesis we collected wood density data of provenance trials from the literature. We used thirty publications published between 1966 and 2015 including 25 species (13 angiosperms and 12 gymnosperms). At the intraspecific level, eight species showed significant positive correlations between wood density and drought conditions of the provenance, two species showed the opposite trend and the remaining 15 species showed no correlation with the climatic conditions of the provenances. For the 10 species with wood density strongly linked to the climatic conditions of the provenance, such relationship reflects a strong genetic determinism and a theoretical fitness optimum. For the other 15 species, wood density does not seem to be the main selection target of drought. This information is critical in the frame of breeding programs for selecting provenances more adaptable to different climate change scenarios.

{debut du text] Phenotypic plasticity is the ability of an organism to change its phenotype in response to changes in the environment. Such an ability varies with genotypes (Pigliucci, 2005; El-Soda et al., 2014) and thus the environment and genotypes can interact to shape phenotypic traits (Via et al., 1995; Pigliucci and Hayden, 2001; Nussey et al., 2007). These interactions are at the basis of evolutionary processes that can, for example, drive natural populations to maladaptive evolution, when the environment is altered by anthropogenic pressures, or select for phenotypic plasticity, when the environment is unstable (Gotthard and Nylin, 1995; Pigliucci, 2005; Postma and van Noordwijk, 2005; Dunlop et al., 2009; Ingleby et al., 2010; Kuparinen and Hutchings, 2012). Genotype by environment interactions (GEI) can also alter community structures and dynamics (Miner et al., 2005). For instance, roots forming a symbiosis with different genotypes of arbuscular mycorrhizal fungi are not affected in the same way by phosphorus availability (Ehinger et al., 2009). On the other hand, the stability of ectomycorrhizal fungal communities can be altered as a consequence of the interactions of plant genotypes with drought conditions (Gehring et al., 2014).

The molecular mechanisms that allow generalist parasitoids to exploit many, often very distinct hosts are practically unknown. The waspAphidius ervi,a generalist koinobiont parasitoid of aphids, was introduced from Europe into Chile in the late 1970s to control agriculturally important aphid species. A recent study showed significant differences in host preference and host acceptance (infectivity) depending on the hostA. erviwere reared on. In contrast, no genetic differentiation betweenA. ervipopulations parasitizing different aphid species and aphids of the same species reared on different host plants was found in Chile. Additionally, the same study did not find any fitness effects inA. erviif offspring were reared on a different host as their mothers. Here, we determined the effect of aphid host species (Sitobion avenaeversusAcyrthosiphon pisumreared on two different host plants alfalfa and pea) on the transcriptome of adultA. ervifemales. We found a large number of differentially expressed genes (between host species: head: 2,765; body: 1,216; within the same aphid host species reared on different host plants: alfalfa versus pea: head 593; body 222). As expected, the transcriptomes from parasitoids reared on the same host species (pea aphid) but originating from different host plants (pea versus alfalfa) were more similar to each other than the transcriptomes of parasitoids reared on a different aphid host and host plant (head: 648 and 1,524 transcripts; body: 566 and 428 transcripts). We found several differentially expressed odorant binding proteins and olfactory receptor proteins in particular, when we compared parasitoids from different host species. Additionally, we found differentially expressed genes involved in neuronal growth and development as well as signaling pathways. These results point towards a significant rewiring of the transcriptome ofA. ervidepending on aphid-plant complex where parasitoids develop, even if different biotypes of a certain aphid host species (A. pisum) are reared on the same host plant. This difference seems to persist even after the different wasp populations were reared on the same aphid host in the laboratory for more than 50 generations. This indicates that either the imprinting process is very persistent or there is enough genetic/allelic variation betweenA. ervipopulations. The role of distinct molecular mechanisms is discussed in terms of the formation of host fidelity.

International audience; Key message Silver fir transplantations along elevational gradients revealed a high diversity but no local adaptation. Populations displayed similar abilities to adapt to new environments including those due to climate change. Context The sustainability of forest stands depends on the ability of species and communities to adapt by combining plasticity and genetic evolution. Although well-documented at the scale of species distributions, the variability and adaptation of forest tree genetic resources are less understood at the short-distance scale. Aims We analysed the effects of genetic and environmental factors on the local-scale phenotypic diversity of traits related to adaptation in Abies alba. We also sought to highlight local adaptation, revealing past selection. Methods Six adaptive traits related to growth, phenology and survival were measured on seedlings from 57 half-sib families collected from 15 provenances and planted in a nine-site reciprocal transplant experiment distributed along three elevational gradients. Results Most part of the phenotypic variability was attributed to the environmental factors. Provenances and families had also significant effects on seedling performances, but the genetic variability was mostly attributed to the families. No pattern of local adaptation was observed, except in the presence of lateral branches in the driest garden. Conclusion The absence of local adaptation suggests a similar ability of all silver fir populations to develop in the various environments. This result provides favourable conditions for coping with the ongoing climate change without exotic resources enrichment.

Tree height-diameter allometry, the link between tree height and trunk diameter, reflects the evolutionary response of a particular species’ allocation patterns to above and belowground resources. As a result, it differs among and within species due to both local adaptation and phenotypic plasticity. These phenotypic variations in tree height-diameter allometry determine tree productivity, resistance and resilience to climate variation and, ultimately, the success of plant material used in restoration projects. We tested the effect of climate change and population origin on the phenotypic variation of tree allometry in four pine species at an early stage of development (ca. 11 years old) based upon data originated from multi-site provenance tests and planted along a wide climatic range in south-western Europe. For a representative sample of populations from each species, we used already-developed species-specific height-diameter allometric models to assess changes in allometry between present and future climatic conditions. We found that Pinus halepensis and Pinus pinaster were the most plastic species, while Pinus sylvestris and Pinus nigra showed negligible plastic responses. In addition, our models stressed that pine tree height-diameter allometry will change and phenotypic variation could increase, except in P. sylvestris, under future environmental conditions. For some of the species, this might allow the selection of phenotypes better suited to novel climatic conditions. These foreseeable changes in tree height-diameter allometry (among and within-species) could entail eco-evolutionary effects on the early forest plantation dynamics. Therefore, restoration and reforestation plans should consider these effects, as they may interfere with production and/or environmental goals. © 2016, Springer Science+Business Media Dordrecht.

Front. Plant Sci. ISI Document Delivery No.: DN3IR Times Cited: 0 Cited Reference Count: 71 Lopez, Rosana Cano, Francisco J. Choat, Brendan Cochard, Herve Gil, Luis Marie Curie fellowship-People Program (Marie Curie Actions) of the European Union's Seventh Framework Program FP7 under REA grant [624473]; Spanish Ministry of Science [AGL2009-10606]; National Parks Authority [SPIP2014-01093] We are grateful to the Canary Islands Government and the Cabildos of Tenerife and Gran Canaria for longstanding support in the study of Canary Island pine. We thank all people involved in the plantation and measurements of the provenance trials and to Christian Bodet and Pierre Conchon for their assistance with the Cavitron in France and Martin Venturas with the centrifuge in Spain. RI, was supported by a Gonzalez Esparcia fellowship during her stay in Clermont-Ferrand and currently holds a Marie Curie fellowship-People Program (Marie Curie Actions) of the European Union's Seventh Framework Program FP7/2007-2013/ under REA grant agreement [624473]. This work was supported by the Spanish Ministry of Science in the Project AGL2009-10606 (VULCAN) and by the National Parks Authority through the project SPIP2014-01093 (PersPiCan). The inspiring discussions during the meetings of the COST action STReESS (COST-FP1106) helped to improve the manuscript. Frontiers media sa Lausanne; International audience; Water availability has been considered one of the crucial drivers of species distribution. However, the increasing of temperatures and more frequent water shortages could overcome the ability of long-lived species to cope with rapidly changing conditions. Growth and survival of natural populations adapted to a given site, transferred and tested in other environments as part of provenance trials, can be interpreted as a simulation of ambient changes at the original location. We compare the intraspecific variation and the relative contribution of plasticity to adaptation of key functional traits related to drought resistance: vulnerability to cavitation, efficiency of the xylem to conduct water and biomass allocation. We use six populations of Canary Island pine growing in three provenance trials (wet, dry, and xeric). We found that the variability for hydraulic traits was largely due to phenotypic plasticity, whereas, genetic variation was limited and almost restricted to hydraulic safety traits and survival. Trees responded to an increase in climate dryness by lowering growth, and increasing leaf-specific hydraulic conductivity by means of increasing the Huber value. Vulnerability to cavitation only showed a plastic response in the driest provenance trial located in the ecological limit of the species. This trait was more tightly correlated with annual precipitation, drought length, and temperature oscillation at the origin of the populations than hydraulic efficiency or the Huber value. Vulnerability to cavitation was directly related to survival in the dry and the xeric provenance trials, illustrating its importance in determining drought resistance. In a new climatic scenario where more frequent and intense droughts are predicted, the magnitude of extreme events together with the fact that plasticity of cavitation resistance is only shown in the very dry limit of the species could hamper the capacity to adapt and buffer against environmental changes of some populations growing in dry locations.

Les études écologiques actuelles montrent que les populations d’ongulés subissent les effets des oscillations climatiques par le biais combiné de facteurs intrinsèques et extrinsèques. La relation plus ou moins fine liant la taille corporelle et l’environnement est par ailleurs débattue depuis de nombreuses années, tant et si bien qu’il existe des lois à portée générale décrivant le phénomène comme celles bien connues (et discutées) de Bergmann (1847) et d’Allen (1877). En contexte archéologique, différents auteurs ont, par le passé, proposé des modèles explicatifs de la variabilité ostéométrique observée chez le renne au niveau des assemblages osseux. Récemment Weinstock a présenté une synthèse sur l’évolution et la variabilité géographique du renne en Europe centrale et occidentale au Pléistocène supérieur. L’auteur insiste notamment sur le caractère multifactoriel des causes de la variation. Dans cette étude nous reprenons une méthodologie déjà éprouvée (utilisation d’indice de taille : les V.S.I. pour Variability Size Index) et analysons plusieurs sites du Sud-Ouest de la France pour présenter une vision diachronique du Pléistocène supérieur à échelle régionale. Des différences significatives au niveau de l’estimation de la taille du renne ont été trouvées durant l’OIS 4, 3 et 2. Les résultats, en accord avec les données faunistiques, palynologiques et sédimentologiques, suggèrent que le climat joue un rôle indirect primordial dans les variations observées. Celles-ci plaident en faveur d’une plasticité phénotypique notable du renne au Pléistocène supérieur et d’une capacité d’acclimatation des individus. L’impact des détériorations et améliorations climatiques paraît plus prononcé chez les femelles que chez les mâles. Toutefois, il ressort également de l’étude que la structure des populations, et en particulier la sex-ratio et le dimorphisme sexuel, doit elle aussi être finement appréciée. Les échantillons analysés constituent un bon référentiel pour une modélisation de l’évolution climatique régionale. Current ecological studies show that the ungulate populations undergo the effects of climatic oscillations through the combination of intrinsic and extrinsic factors. Furthermore, the close relationship between body size and environment has been discussed for several years. This led to the elaboration of general laws such as that of the well-known and discussed Bergmann (1847) and Allen (1877) laws describing the phenomenon. As far as the archaeological context is concerned, different authors suggested explicative patterns of the osteometrical variability observed on the reindeer. Recently, Weinstock synthesised reindeer body size evolution and its geographical variability in Central and Western Europe during the Late Pleistocene. Theauthor insists on the multivariate character of the causes. In the present study, several South-western French sites are studied in order to obtain a diachronic vision of the Late Pleistocene within a regional scale. A well known methodology is used (apply of size index: V.S.I. for Variability Size Index). Significant differences in reindeer body size estimation were found at OIS 4, 3 and 2. According to faunal, palynological and sedimentological data, it seems that the climate played an important role in body size changes, highlighting great phenotypic plasticity in Late Pleistocene reindeer. Particularly, female body size showed greater variation than males. However, our study also shows that data concerning the population structure, and particularly the sex ratio and the sexual dimorphism, must be taken into account.

Selection and plasticity are two mechanisms that allow the adaptation of a population to a changing environment. Interaction between these nonexclusive mechanisms must be considered if we are to understand population survival. This review discusses the ways in which plasticity and selection can interact, based on a review of the literature on selection and phenotypic plasticity in the evolution of populations. The link between selection and phenotypic plasticity is analysed at the level of the individual. Plasticity can affect an individual’s response to selection and so may modify the end result of genetic diversity evolution at population level. Genetic diversity increases the ability of populations or communities to adapt to new environmental conditions. Adaptive plasticity increases individual fitness. However this effect must be viewed from the perspective of the costs of plasticity, although these are not easy to estimate. It is becoming necessary to engage in new experimental research to demonstrate the combined effects of selection and plasticity for adaptation and their consequences on the evolution of genetic diversity.

Tradeoffs lead to antagonistic relationships between phenotypic traits and are thought to be determined both genetically and environmentally. We present here an allocation model that distinguishes between the genetic and environmental components of variation in resource allocation. In this model we introduced plasticity of resource allocation which was considered to be an adaptive response to environmental variations. The results show that resource allocation plasticity is a key parameter for the existence of environmental (i.e. inter environments and intra genotype) correlations and is therefore necessary to detect environment-induced tradeoffs. We also investigated the impact of the resource allocation plasticity and other factors on genetic (i.e. inter genotypes) correlations. Our results show that resource allocation plasticity induces a masking effect of tradeoffs when studying genetic correlations and increases the masking effect of resource variation by making apparent correlations positive when negative correlations are expected. In addition, by simulating different sources of resource acquisition variation, we demonstrated that resource variation might have different effects on correlations according to the experimental design and the studied biological material. Further development of this model may be used to investigate the theoretical implications of tradeoffs in evolutionary biology and to improve design and interpretation of experimental studies.

International audience; Crown shape of four different clones planted out in six experimental fields located in five European countries are described and compared using discriminant analysis. The correlations among the considered traits were computed for each clone in each location. The results of the discriminant analysis showed that the locations in which trees have grown have a greater discriminating effect than the clones themselves. It means that the ecological factors that characterize a particular location effectively mould the shape of the tree's crown. The phenotypic correlations between characters were altered when trees grow in different conditions. For one of the clones taken into account these changes are due to the differential phenotypic plasticity of the considered traits. This characteristic may have considerable implications on the breeding programs. A question is whether it is worth the effort to select clones from a particular environment and then use them under very different conditions of habitat.; L'effet du milieu sur la forme des houppiers du cyprès. On décrit ici la forme des houppiers de 4 clones différents plantés dans 6 essais expérimentaux de 5 pays européens et on les compare entre eux par une analyse discriminante. Les corrélations entre les traits considérés ont été calculées pour chaque clone dans chaque localité. Les résultats des analyses discriminantes ont montré que les localités où les clones ont poussé sont plus discriminantes que les clones. Cela signifie que les facteurs écologiques caractéristiques d'une localité sont capables de modeler la forme des houppiers. Les corrélations phénotypiques entre caractères sont altérées si les arbres ont poussé dans des conditions différentes. Pour un des clones étudiés ces changements sont provoqués par la différente plasticité phénotypique des traits considerés. Cette caractéristique peut avoir des profondes implications sur les programmes d'amélioration génétique. La question est de savoir s'il vaut la peine de sélectionner des clones provenant d'un habitat particulier pour les employer dans des conditions très différentes.

An adaptation of the von Bertalanffy growth model is formulated to describe the phenotypic plasticity of fish somatic growth in relation to trophic conditions. The model is developed for the North sea Downs herring (Clupea harengus). II suggests that annual growth variability during 1974-1990 was mainly due to the combined effects of herring abundance and wind-induced turbulence (coincident with the spring stratification of the water column). Springtime turbulences cause reduced and delayed planktonic blooms preceding the annual foraging period of Downs herring. The negative relation observed between herring abundance and growth is hypothesized to be due to intra-specific competition for trophic resources. Incorporated into the calculation of yield per recruit, the established growth model provides slightly more optimistic diagnoses while dropping the classic assumption of constant weight at age. (C) Ifremer/Elsevier, Paris., Une adaptation du modèle de croissance de Von Bertalanffy est proposée afin d'exprimer une plasticité phénotypique de la croissance somatique des poissons en fonction des conditions trophiques. Le modèle est développé sur l'exemple du hareng des Downs en mer du Nord (Clupea harengus). Sur la période 1974–1990, l'ajustement du modèle suggère que la variabilité interannuelle de croissance en longueur est principalement due à l'action conjointe de deux facteurs: la croissance est reliée négativement à l'abondance des harengs et à la turbulence due au vent (contemporaine de la stratification printanière de la colonne d'eau). Des turbulences trop importantes sont en effet supposées diminuer et retarder le pic du bloom planctonique précédant la phase annuelle de nutrition des harengs. En outre, la relation négative entre l'abondance des harengs et leur croissance est interprétée comme une conséquence de la compétition intraspécifique pour les ressources trophiques. Des simulations de rendement par recrue à partir du modèle de croissance proposé montrent que la prise en compte d'une croissance dépendant de la densité fournit des diagnostics légèrement plus optimistes.

International audience; Phenotypic plasticity is a key mechanism associated with the spread of exotic plants and previous studies have found that invasive species are generally more plastic than co-occurring species. Comparatively, the evolution of phenotypic plasticity in plant invasion has received less attention, and in particular, the genetic basis of plasticity is largely unexamined. Native from North America, Acer negundo L. is aggressively impacting the riparian forests of southern and eastern Europe thanks to higher plasticity relative to co-occurring native species. We therefore tested here whether invasive populations have evolved increased plasticity since introduction. The performance of 1152 seedlings from 8 native and 8 invasive populations was compared in response to nutrient availability. Irrespective of nutrients, invasive populations had higher growth and greater allocation to above-ground biomass relative to their native conspecifics. More importantly, invasive genotypes did not show increased plasticity in any of the 20 traits examined. This result suggests that the high magnitude of plasticity to nutrient variation of invasive seedlings might be pre-adapted in the native range. Invasiveness of A. negundo could be explained by higher mean values of traits due to genetic differentiation rather than by evolution of increased plasticity.

International audience; 1. Rapid climate change both imposes strong selective pressures on natural populations – potentially reducing their growth rate and causing genetic evolution – and affects the physiology and development of individual organisms. Understanding and predicting the fates of populations under global change, including extinctions and geographical range shifts, requires analysing the interplay of these processes, which has long been a grey area in evolutionary biology. 2. We review recent theory on the interaction of phenotypic plasticity, genetic evolution and demography in environments that change in time or space. We then discuss the main limitations of the models and the difficulties in testing theoretical predictions in the wild, notably regarding changes in phenotypic selection, the evolution of (co)variances of reaction norm parameters, and transient dynamics. 3. We use two landmark examples of physiological responses to climate change –trees facing drier climate and extreme temperatures, and marine phytoplankton under rising CO2 – to highlight relatively neglected questions and indicate the theoretical and empirical challenges that they raise. These examples illustrate notably that age-specific patterns of plasticity and selection on the one hand, and changes in community interactions and functioning on the other hand, need to be further investigated theoretically and empirically for a better understanding of evolutionary demographic responses to climate change in the wild.

The sequencing of the genome of the pea aphid Acyrthosiphon pisum revealed an unusual expansion of the miRNA machinery, with two argonaute-1, two dicer-1 and four pasha gene copies. In this report, we have undertaken a deeper evolutionary analysis of the phylogenetic timing of these gene duplications and of the associated selective pressures by sequencing the two copies of ago-1 and dcr-1 in different aphid species of the subfamily Aphidinae. We have also carried out an analysis of the expression of both copies of ago-1 and dcr-1 by semi-quantitative PCR in different morphs of the pea aphid life cycle., The analysis has shown that the duplication of ago-1 occurred in an ancestor of the subfamily Aphidinae while the duplication of dcr-1 appears to be more recent. Besides, it has confirmed a pattern of one conserved copy and one accelerated copy for both genes, and has revealed the action of positive selection on several regions of the fast-evolving ago-1b. On the other hand, the semi-quantitative PCR experiments have revealed a differential expression of these genes between the morphs of the parthenogenetic and the sexual phases of Acyrthosiphon pisum., The discovery of these gene duplications in the miRNA machinery of aphids opens new perspectives of research about the regulation of gene expression in these insects. Accelerated evolution, positive selection and differential expression affecting some of the copies of these genes suggests the possibility of a neofunctionalization of these duplicates, which might play a role in the display of the striking phenotypic plasticity of aphids.

Background To identify the determinants of invasiveness, comparisons of traits of invasive and native species are commonly performed. Invasiveness is generally linked to higher values of reproductive, physiological and growth-related traits of the invasives relative to the natives in the introduced range. Phenotypic plasticity of these traits has also been cited to increase the success of invasive species but has been little studied in invasive tree species. In a greenhouse experiment, we compared ecophysiological traits between an invasive species to Europe, Acer negundo, and early- and late-successional co-occurring native species, under different light, nutrient availability and disturbance regimes. We also compared species of the same species groups in situ, in riparian forests. Results Under non-limiting resources, A. negundo seedlings showed higher growth rates than the native species. However, A. negundo displayed equivalent or lower photosynthetic capacities and nitrogen content per unit leaf area compared to the native species; these findings were observed both on the seedlings in the greenhouse experiment and on adult trees in situ. These physiological traits were mostly conservative along the different light, nutrient and disturbance environments. Overall, under non-limiting light and nutrient conditions, specific leaf area and total leaf area of A. negundo were substantially larger. The invasive species presented a higher plasticity in allocation to foliage and therefore in growth with increasing nutrient and light availability relative to the native species. Conclusions The higher level of plasticity of the invasive species in foliage allocation in response to light and nutrient availability induced a better growth in non-limiting resource environments. These results give us more elements on the invasiveness of A. negundo and suggest that such behaviour could explain the ability of A. negundo to outperform native tree species, contributes to its spread in European resource-rich riparian forests and impedes its establishment under closed-canopy hardwood forests.

International audience; Species distributed along wide environmental ranges are expected to be either plastic or adapted to local optima. The elucidation of which of these alternatives prevails, is crucial in planning breeding and conservation strategies for not yet domesticated species. Austrocedrus chilensis (Cupressaceae) is the most commercially important conifer of the temperate forests of Argentina and the target of a domestication program. A steep precipitation gradient characterizes its Argentinean range.* Variation within and differentiation among four natural populations of this Patagonian cypress representative of two contrasting precipitation regimes (>1300 and 330 mm per y) were assessed by analyzing several morpho/architectural traits in one-year-old seedlings grown in a greenhouse. * Progenies from one of the two xeric populations did not differ from those corresponding to both humid-site populations. The two most variable populations in terms of additive genetic variance belonged to contrasting precipitation regimes. Differentiation among populations was low as measured by each and every variable (average Qst = 0.088). Morphological traits related to the main axis size would have a dubious adaptive meaning.* The results suggest that the Patagonian cypress would have not evolved genetic pools adapted to local optima, and thus it appears to be a phenotypically plastic species, at least regarding growth at juvenile age.; Les espèces presentant de vastes aires de répartition avec des fortes variations de l'environnement sont soit plastiques, soit adaptées à des optima locaux. Identifier laquelle de ces deux alternatives est celle qui prévaut est une étape cruciale pour planifier des stratégies d'amélioration génétique ou de conservation d'espèces non encore domestiquées. Austrocedrus chilensis (Cupressaceae) est le conifère le plus important du point de vue commercial dans les forêts tempérées d'Argentine et fait l'object d'un programme de domestication. Un fort gradient de précipitations caractérise son aire de répartition en Argentine.* Les variations intra-population et la différenciation entre quatre populations naturelles représentatives de deux régimes contrastés de précipitations (>1300 mm et 330 mm par an) ont été évaluées en analysant plusieurs traits d'architecture et de morphologie sur des plants âgés de un an cultivés sous serre.* Les descendants de l'une des deux populations xériques ne différaient pas de ceux des deux populations de sites humides. Les deux populations avec la plus forte variance génétique additive provenaient de régimes contrastés de précipitation. La différenciation entre populations était faible tant pour chaque trait que pour l'ensemble des traits (Qst = 0.088). Les caractéristiques morphologiques liées à la taille de l'axe principal n'auraient donc que peu signification en termes d'adaptation.* Les résultats suggèrent que le cyprès de Patagonie n'aurait pas développé de pools génétiques adaptés aux optima locaux. Il semble être une espèce phénotypiquement plastique, au moins en ce qui concerne la croissance au stade juvénile.

Current models in evolutionary ecology predict life history alterations in response to habitat suitability to optimize fitness. Only few empirical studies have demonstrated how life history traits that are expected to trade off against each other differ among environments. In Europe, many salt marshes have been recently invaded by the grass Elymus athericus. Previous studies however showed higher densities of the endangered spider Arctosa fulvolineata (Araneae: Lycosidae) in invaded salt marshes compared to natural habitats, which suggests a lower habitat suitability in the latter. The aim of this study was to determine if this emerging habitat (1) affects the amount of resource acquisition and (2) alters the balance between life history traits that are expected to trade off against each other in this stenotopic salt marsh species. As suggested by theoretical studies, an optimization of fitness by increasing egg size at the cost of decreasing fecundity in unsuitable (i.e., natural) habitats was expected. Females presenting cocoon were then collected in close invaded and natural salt marsh areas within the Mont Saint-Michel Bay (France). By considering female mass as covariate, cocoon mass, number of eggs, and egg volume were compared between both habitats. Clutch mass was strongly determined by female mass in both habitats. Clutch mass was however significantly smaller in the natural habitat compared to the invaded habitat, indicating a higher resource acquisition in the latter. When correcting for female size, fecundity was additionally increased in the invaded habitat through a significant decrease in egg size. This phenotypic response can be explained by differences in habitat structure between invaded and natural habitats: the former offers a more complex litter favoring nocturnal wanderers like A. fulvolineata. The existence of such an adaptive reproduction strategy depending on habitat suitability constitutes an original case of an invasion that favors an endangered species.

Irradiance elicits a large plasticity in leaf traits, but little is known about the modulation of this plasticity by ontogeny. Interactive effects of relative irradiance and ontogeny were assessed on leaf traits for two tropical rainforest tree species: Dicorynia guianensis Amshoff and Tachigali melinonii (Harms) Barneby (Fabaceae, Caesalpinioideae). Eleven morphological and physiological leaf traits, relative to photosynthetic performance, were measured on saplings at three different architectural development stages (ASD 1, 2 and 3) and used to derive composite traits like photosynthetic N-use efficiency. Measurements were made along a natural irradiance gradient. The effect of ASD was very visible and differed between the two species. For Dicorynia guianensis, only leaf mass-per-area (LMA) significantly increased with ASDs whereas for Tachigali melinonii, almost all traits were affected by ASD: LMA, leaf N content and photosynthetic capacity increased from ASD 1 to ASD 3. Photosynthetic N-use-efficiency was not affected by ASD in any species. Leaf traits were severely modulated by irradiance, whereas the degree of plasticity was very similar among ASDs. Only few interactions were detected between irradiance and ASD, for leaf thickness, carbon content, and the ratio Chl/N in T. melinonii and for photosynthetic capacity in D. guianensis. We conclude that ontogenic development and irradiance-elicited plasticity modulated leaf traits, with almost no interaction, i.e., the degree of irradiance-elicited plasticity was stable across development stages and independent of ontogeny in these two species, at least in the early stages of development assessed here., Les traits foliaires varient fortement avec l'éclairement mais également avec l'ontogenèse. Cependant, l'impact de l'ontogenèse sur la plasticité induite par l'éclairement reste mal connu. Les interactions entre ontogenèse et éclairement relatif ont ainsi été étudiées pour des traits fonctionnels foliaires de deux espèces de forêt tropicale humide de Guyane française : Dicorynia guianensis Amshoff et Tachigali melinonii (Harms) Barneby (Fabaceae, Caesalpinioideae). • Onze traits morphologiques et physiologiques foliaires, relatifs aux capacités photosynthétiques, ont été mesurés sur de jeunes arbres ayant atteint trois stades architecturaux de développement successifs (ASD 1, 2 et 3) et utilisés pour en déduire des traits composites. Les mesures ont été réalisées le long d'un gradient naturel d'éclairement en forêt. • L'impact de stades successifs de développement différait entre espèces. Pour D. guianensis, seule la masse surfacique (LMA) a augmenté significativement avec les stades de développement tandis que pour T. melinonii, presque tous les traits foliaires étaient modulés. Pour cette espèce, LMA, teneur en N et capacité photosynthétique ont augmenté de ASD 1 à ASD 3. Par contre, l'efficience d'utilisation de N par la photosynthèse est restée stable entre ASDs. • Les traits foliaires ont été fortement modifiés par l'éclairement mais le degré de plasticité était similaire entre les ASDs. Des interactions entre ASD et éclairement n'ont été observées que pour l'épaisseur, la teneur en C et le rapport Chl/N de T. melinonii ainsi que pour la capacité photosynthétique de D. guianensis. • En dépit de l'effet significatif de l'ontogénèse sur les traits foliaires, seules de très faibles interactions ont pu être détectées avec l'éclairement pour les deux espèces. On peut en conclure que les stades successifs de développement ne modifient pas le degré de plasticité foliaire en réponse à l'éclairement tout au moins dans le cas des stades jeunes pris en compte ici.

International audience; In a global warming scenario, drought and heat waves like the one that occurred in 2003 in Europe are expected to become more intense and frequent. This extreme climate event strongly affected the hydraulic balance in many forest tree species including Douglas-fir, with symptoms ranging from partial crown necrosis to death. We studied a French Douglas-fir provenance trial, strongly affected by the 2003 drought and heat wave. Using wood X-ray microdensity profiles as a record of cambium response to environmental variations, we compared mean stem density and growth between dead and alive neighbouring trees and several microdensity characters measured over 17 growth rings previous to 2003. Special attention has been given to the sampling layout in order to minimize the micro-environmental effects. At tree level, surviving trees have a significantly higher mean stem density. At tree ring level, they have a significantly higher mean ring density, maximum ring density, latewood density and, to a lesser extent, latewood proportion. No significant difference was found for diameter growth. These results could have direct implications in the way to study and predict possible acclimation and adaptation of forest trees to climate change process. Wood could be used for the selection of genotypes with a desirable plasticity and resistance to drought induced-cavitation.