Outlook for an integrated sustainable development of pig production in the Red River Delta

224pThe situation in Thai Binh province offers a significant number of assets to be capitalized upon in terms of recycling of effluents, but the stakeholders concerned have an urgent need for strong measures to help them live from their livestock farming activity while protecting an endangered environment. This chapter highlights the additional agronomical and economic references as well as decision making tools that still need to be acquired. The technical and organizational solutions that will need to be tested or promoted more widely are presented. The key issues for the future and the establishment of a hierarchy or priorities in terms of support for agricultural development, necessary local know-how and avenues of research to study in more depth the complex problems encountered in North Vietnam are discussed. Emphasis is given on the pig production in the Red River Delt

Prévision de l’impact des espèces invasives : un examen de l’approche par comparaison des réponses fonctionnelles

Dans l’objectif d’optimiser les stratégies de gestion des espèces invasives, la science des invasions fait face au besoin d’anticiper et de hiérarchiser les invasions futures à l’aide d’approches efficaces, économiques et généralisables à de nombreux groupes taxinomiques. Récemment, pour prédire l’impact des prédateurs invasifs, il a été proposé de comparer la relation entre la ressource consommée et sa disponibilité, c’est-à-dire la réponse fonctionnelle, entre des envahisseurs potentiels et leurs analogues trophiques dans l’écosystème receveur (approche par comparaison des réponses fonctionnelles, ou approche CRF ci-après). Après une brève description du cadre de travail de l’approche CRF, nous dressons le bilan des comparaisons déjà disponibles dans la littérature. Ensuite, nous examinons comment la présence de congénères du prédateur peut altérer les prédictions de l’approche CRF. En effet, dans les expériences menées dans le cadre de l’approche CRF, les réponses fonctionnelles ont été déterminées en faisant varier la densité en proies mais avec un unique individu prédateur alors que dans la nature, les prédateurs sont rarement isolés et sont donc susceptibles d’interagir entre eux pendant leur activité d’approvisionnement. Ces interactions peuvent altérer l’efficacité de chaque individu, générant ainsi une prédateur-dépendance dans la réponse fonctionnelle. Cette interférence mutuelle peut affecter différemment le prédateur invasif et son analogue natif et par conséquent moduler la différence entre leurs réponses fonctionnelles. La prise en compte de l’interférence devrait améliorer l’extrapolation des résultats de l’approche CFR aux populations naturellesIn the aim of optimizing management strategies, invasion science faces the need to prioritize future invasions with reliable, cost-effective and generalizable approaches. To predict the ecological impact of invasive species, it has recently been proposed to compare the relationship between resource consumption and resource availability, namely the functional response, between potential invaders and their trophic analogs in the recipient ecosystem. After a brief description of the framework of the comparative functional response approach (CFR approach hereafter), we review the functional response comparisons already available in the literature. We then investigate how the presence of conspecifics of the predators may alter predictions of the CFR approach. Indeed, the functional response experiments carried under the CFR approach typically involve a range of prey densities but a single predator individual whereas predators rarely forage alone in nature. Mutual interference between predators can generate predator dependence in the FR through the alteration of per capita consumption rates. Mutual interference is therefore likely to modulate the difference in functional response between an invasive predator and its native counterpart, and accounting for mutual interference should promote extrapolation of results to natural population

Feeding choice and predation pressure of two invasive gammarids, Gammarus tigrinus and Dikerogammarus villosus, under increasing temperature

International audienc

Intra- and inter-continental variation in the functional responses of a high impact alien invasive fish

Recently, a body of literature has indicated the utility of comparisons among introduced and native species of their functional responses, that is, the relationship between resource use (e.g. predator consumption rate) and resource availability (e.g. prey density) to predict their impact. However, a key feature of this methodology, that has not yet been examined, is the degree to which the functional response curves of an introduced species differ within and between its native and introduced geographical ranges. Information on the variation in functional responses is key to make robust assessments on the ecological impact and to assess possible differences between native and invasive species. Here, we examine the predatory functional responses in multiple native and introduced populations of a globally high impact alien invasive fish, the topmouth gudgeon (Pseudorasbora parva). In standardised aquaria and with two prey species, significant differences in the functional responses among and between different populations occurring in the native and the invaded range were found. Among populations in the native range, the functional response indicated little variation, and fish always showed a Type II response, irrespective of the type of prey used. In the introduced range, populations showed a Type II response when fed chironomid larvae as prey, while a Type III response was observed when feeding Daphnia magna. Populations in the invaded range consumed overall more prey when fed D. magna compared to the populations in the native range. When feeding chironomid larvae, no consistent trend was observed. Context dependencies as well as species-specific traits and fish density most likely play an important role when comparing the functional response between populations occurring in their native and invaded ranges

When worlds collide: Invader-driven benthic habitat complexity alters predatory impacts of invasive and native predatory fishes

Interactions between multiple invasive alien species (IAS) might increase their ecological impacts, yet relatively few studies have attempted to quantify the effects of facilitative interactions on the success and impact of aquatic IAS. Further, the effect of abiotic factors, such as habitat structure, have lacked consideration in ecological impact prediction for many high-profile IAS, with most data acquired through simplified assessments that do not account for real environmental complexities. In the present study, we assessed a potential facilitative interaction between a predatory invasive fish, the Ponto-Caspian round goby (Neogobius melanostomus), and an invasive bivalve, the Asian clam (Corbicula fluminea). We compared N. melanostomus functional responses (feeding-rates under different prey densities) to a co-occurring endangered European native analogue fish, the bullhead (Cottus gobio), in the presence of increased levels of habitat complexity driven by the accumulation of dead C. fluminea biomass that persists within the environment (i.e. 0, 10, 20 empty bivalve shells). Habitat complexity significantly influenced predation, with consumption in the absence of shells being greater than where 10 or 20 shells were present. However, at the highest shell density, invasive N. melanostomus maximum feeding-rates and functional response ratios were substantially higher than those of native C. gobio. Further, the Relative Impact Potential metric, by combining per capita effects and population abundances, indicated that higher shell densities exacerbate the relative impact of the invader. It therefore appears that N. melanostomus can better tolerate higher IAS shell abundances when foraging at high prey densities, suggesting the occurrence of an important facilitative interaction. Our data are thus fully congruent with field data that link establishment success of N. melanostomus with the presence of C. fluminea. Overall, we show that invader-driven benthic habitat complexity can alter the feeding-rates and thus impacts of predatory fishes, and highlight the importance of inclusion of abiotic factors in impact prediction assessments for IAS

Assessing the ecological impacts of invasive species based on their functional responses and abundances

Invasive species management requires allocation of limited resources towards the proactive mitigation of those species that could elicit the highest ecological impacts. However, we lack predictive capacity with respect to the identities and degree of ecological impacts of invasive species. Here, we combine the relative per capita effects and relative field abundances of invader as compared to native species into a new metric, “Relative Impact Potential” (RIP), and test whether this metric can reliably predict high impact invaders. This metric tests the impact of invaders relative to the baseline impacts of natives on the broader ecological community. We first derived the functional responses (i.e. per capita effects) of two ecologically damaging invasive fish species in Europe, the Ponto-Caspian round goby (Neogobius melanostomus) and Asian topmouth gudgeon (Pseudorasbora parva), and their native trophic analogues, the bullhead (Cottus gobio; also C. bairdi) and bitterling (Rhodeus amarus), towards several prey species. This establishes the existence and relative strengths of the predator-prey relationships. Then, we derived ecologically comparable field abundance estimates of the invader and native fish from surveys and literature. This establishes the multipliers for the above per capita effects. Despite both predators having known severe detrimental field impacts, their functional responses alone were of modest predictive power in this regard; however, incorporation of their abundances relative to natives into the RIP metric gave high predictive power. We present invader/native RIP biplots that provide an intuitive visualisation of comparisons among the invasive and native species, reflecting the known broad ecological impacts of the invaders. Thus, we provide a mechanistic understanding of invasive species impacts and a predictive tool for use by practitioners, for example, in risk assessments

Parasites as mediators of biotic interactions within a lotic subjected to species introductions the case of infection by the acanthocephalan Polymorphis minutus in the amphipod Gammarus roeseli

Les communautés biologiques contemporaines des écosystèmes soumis aux glaciations regroupent des espèces dont le passé coévolutif est parfois faible voire inexistant. Si le déplacement d’un organisme hors de son aire de répartition originelle est un processus naturel, la connectivité des hydrosystèmes à une échelle internationale augmente la fréquencedes introductions et la quantité d’organismes déplacés dans les écosystèmes lotiques.L’aptitude de l’espèce exotique à proliférer au-delà de son point d’introduction, autrement dit son potentiel invasif, va dépendre en partie des relations biotiques qu’elle entretient avec la faune en place.L’incorporation aux réseaux trophiques étant leur principal mode de transmission, les parasites peuvent modifier l’issue d’une interaction entre un prédateur et sa proie. Ainsi les parasites dont le cycle de vie implique plusieurs hôtes sont connus pour leur capacité à manipuler le comportement de leur hôte intermédiaire qui devient alors vulnérable à la prédation par l’hôte définitif. Par conséquent, dans un contexte d’invasions biologiques, le parasitisme peut conditionner le devenir des espèces en interaction dans un écosystème receveur. Gammarus roeseli est un crustacé amphipode originaire des Balkans et très bien représenté à l’Ouest de l’Europe. Compte tenu de sa relative ancienneté sur le territoire français, il est considéré comme naturalisé dans la Nied, un cours d’eau situé au Nord-est de la France. G. roeseli sert d’hôte intermédiaire à de nombreux parasites à cycle de vie complexe à l’instar de l’acanthocéphale d’oiseau Polymorphus minutus. Il s’agissait dans un premier temps de dresser le profil écologique des amphipodes infectés pour, entre autres, identifier les facteurs abiotiques et biotiques qui influencent la distribution spatiale de la population hôte. Dans un deuxièmetemps, l’objectif fut de caractériser le comportement de fuite de l’hôte intermédiaire face au gammare exotique Dikerogammarus villosus et face à l’épinoche à trois épines, un poisson natif. Ces deux prédateurs ne risquent pas l’infection avec P. minutus et représentent par conséquent une mort certaine pour le parasite s’ils ingèrent un crustacé infecté.Les investigations in natura et les tests en laboratoire montrent que l’infection avec P. minutus change les profils écologiques et comportementaux de G. roeseli. Dans la Nied, la fraction infectée de la population se cantonnait aux habitats de surface contrairement aux autres réagissaient différemment aux stimuli physiques et chimiques comparativement à leurs congénères non parasités, et par conséquent étaient significativement moins consommés par D.villosus et par l’épinoche lors d’expériences menées en microcosmes.Globalement, cette étude apporte des précisions quant au rôle sélectif des prédateurs non hôtes dans l’évolution des stratégies parasitaires, et suggère que les parasites peuvent bénéficier de l’augmentation de certains comportements anti-prédateurs, pré-existant chez l’hôte intermédiaire, pour éviter une mort certaine dans une espèce non compatible. Les implicationsdu parasitisme en termes d’exclusion compétitive dans un écosystème receveur sont également discutéesCurrent biological communities of ecosystems subjected to glaciations gather species with a low, or no, coevolutionary history. If the translocation of a species from its original range to a new area is a natural process, the hydrological connectivity at the international scale increases the introduction rate and the amount of translocated species within lotic ecosystems. The ability for the exotic species to spread beyond its introduction point, in other words its invasive potential, will depend partially on the biotic interactions between this species and the local fauna.Incorporation within trophic networks being their main mode of transmission, parasites can modify the outcome of predator / prey interactions. Parasites whose life-cycle involves several species are known for their ability in manipulating the behaviour of the intermediate host, which becomes vulnerable to predation by the ultimate host. Consequently, in a biological invasion context, parasitism can influence the success of interacting species within a recipient ecosystem.Gammarus roeseli is crustacean amphipod of Balkan origin which is widespread in WesternEurope. As G. roeseli is not a recent species regarding its first record from the French territory, gammarids found in the river Nied, a stream located in North - eastern France, are expected to belong to a naturalized population. G. roeseli serves as an intermediate host for various complex lifecycle parasites including the bird acanthocephalan Polymorphus minutus. The first aim of this study was to assess the ecological profile of infected amphipods so as to identify, inter alia, the biotic andabiotic parameters that influence the spatial distribution of the host population. The second aim was to investigate the escape behaviour of the intermediate host facing the invasive gammarid Dikerogam-marus villosus, or facing the native three-spine stickleback. These two predators do notrisk infection with P. minutus and so represent a dead-end for the parasite if either D. villosus or sticklebacks eat infected crustaceans.Both in situ investigations and laboratory tests showed that infection with P. minutus affects the ecological and behavioural profiles of G. roeseli. In the river Nied, the infected fraction of the population gathered in surface habitats whereas other invertebrates were mostly benthic. Under predation risk, infected amphipods reacted differently to physical and chemical stimuli than uninfected conspecifics, and thus were significantly less preyed upon by D. villosus and sticklebacksduring microcosm experiments.Overall, this study brings new insights regarding the selective role of non-host predators in shaping the evolution of parasitic strategies, and suggests that parasites may benefit of increasing some natural anti-predatory adaptations of their intermediate hosts to avoid a dead-end within unsuitable species. Results are also discussed in terms of species replacement in a recipient ecosyste

Bird and amphipod parasites illustrate a gradient from adaptation to exaptation in complex life cycle.

6 pagesInternational audienceTrophically transmitted parasites modify the phenotype of their hosts, sometimes in a way that facilitates transmission. Parasite-induced changes can be either part of a manipulative strategy evolved to improve the transmission success of the parasite, or simply by-products of infection with no health effect. In the former case, manipulation is regarded as a parasite adaptation driven by the probability of being eaten by a suitable next host. Here, we consider the fact that manipulation may also be an 'exaptation': a trait that evolved for a certain use, but which has been co-opted for a new use. According to this view, features built by natural selection for their role (historical genesis) and current utility features at present enhancing fitness of the parasite are different. We describe the behavioural profile of a freshwater crustacean (Gammarus roeseli) when serving as intermediate host to an acanthocephalan parasite (Polymorphus minutus). Although host manipulation by P. minutus is assumed to favour predation by avian definitive hosts (current utility feature), its evolution has been driven by the probability of dying inside non-host predators (historical genesis). This example of an exaptation, taken together with examples of adaptations in closely related host-parasite associations, improves our understanding of the evolutionary genesis of parasites' transmission strategies

Evolution of Predator Foraging in Response to Prey Infection Favors Species Coexistence

Abstract As acknowledged by Optimal Foraging theories, predator diets depend on prey profitability. Parasites, ubiquitous in food webs, are known to affect simultaneously host vulnerability to predation and host energy contents, thereby affecting profitability. In this work, we study the eco-evolutionary consequences of prey infection by a non trophically-transmitted parasite, with a simple lifecycle, on predator diet. We also analyze the consequences for coexistence between prey, predators and parasites. We model a trophic module with one predator and two prey species, one of these prey being infected by a parasite, and distinguish between two effects of infection: a decrease in host fecundity (virulence effect) and an increase in vulnerability to predation (facilitation effect). Predator foraging may evolve toward specialist or generalist strategies, the latter being less efficient on a given resource. We show that the virulence effect leads to specialisation on the non-infected prey while the facilitation effect, by increasing prey profitability, favors specialisation on the infected prey. Combining the two effects at intermediate intensities promotes either generalist predators or the diversification of foraging strategies (coexistence of specialists), depending of trade-off shape. We then investigate how the evolution of predator diet affects the niche overlap between predator and parasite. We show that facilitation effects systematically lead to a high niche overlap, ultimately resulting in the loss of the parasite. Virulence effects conversely favor coexistence by allowing a separation of the predator and parasite niches

Parasite-induced suppression of aggregation under predation risk in a freshwater amphipod: sociality of infected amphipods.

7 pagesInternational audienceRecent findings suggest that grouping with conspecifics is part of the behavioural defences developed by amphipod crustaceans to face predation risk by fish. Amphipods commonly serve as intermediate hosts for trophically transmitted parasites. These parasites are known for their ability to alter intermediate host phenotype in a way that promotes predation by definitive hosts, where they reproduce. If aggregation in amphipods dilutes the risk to be preyed on by fish, then it may dilute the probability of transmission for the parasite using fish as definitive hosts. Using experimental infections, we tested whether infection with the fish acanthocephalan Pomphorhynchus laevis alters attraction to conspecifics in the amphipod intermediate host Gammarus pulex. We also measured G. pulex's activity and reaction to light to detect potential links between changes in aggregation and changes in other behaviours. The attraction to conspecifics in the presence of predator cue, a behaviour found in uninfected gammarids, was cancelled by the infection, while phototaxis was reversed and activity unchanged. We found no correlation between the three behaviours in infected amphipods, while activity and aggregation were negatively correlated in uninfected individuals after the detection of predation cue. The physiological causes and the adaptive value of aggregation suppression are discussed in the context of a multidimensional manipulation