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An inventory of the species in and around the clove agroforestry systems (AFS) on the east coast of Madagascar revealed that none of the currently grown species derive from the native Malagasy biodiversity: the herbaceous and woody plants which comprise planned agrobiodiversity, i.e. are deliberately planted by the farmer, are without exception, introduced species. The associated agrobiodiversity, including plants that grow spontaneously and are protected or tolerated by farmers, is composed of a mix of native and introduced species. This situation, which is paradoxical for an island with a very high level of endemicity is the result of a double process of species introduction. The first is associated with the waves of migration, which, during the past three thousand years or so, allowed colonisation of the island, previously devoid of human occupants. The migrant populations originating from Austronesia and then from Africa, introduced their own crops and associated growing practices and only exploited local biodiversity through gathering, which did not require planting or tending. This situation is therefore the result of a long process of farmers' strategies to manage natural resources in a context of subsistence agriculture. The second process is more recent and is associated with increasing occupation by Europeans from the 16th/eighteenth century onwards, which peaked at the end of the nineteenth century with the French colonisers, who introduced and then developed cash crops (coffee, cloves, vanilla). This long-term retrospective study sheds light on the dynamics at the origin of the biodiversity "melting pot" visible today in the AFS along the east coast of Madagascar. It shows the constant evolution and adaptation of farmers' strategies and cropping systems, but also their historical roots. The cohabitation between introduced and indigenous species, observed today in Madagascar, is found in other AFSs built around an introduced cash crop, in various tropical zones. Knowing the origins and determinants of this cohabitation could be useful to support future evolutions of these cropping systems in the current context of changing agricultural practices in response to ecological and macroeconomic pressures.

International audience; Ambrosia trifida L. (giant ragweed, Asteraceae) is native to the North American continent and was introduced into Europe and Asia at the end of the 19th century. In its native range, this tall annual species is common in riparian and ruderal habitats and is also a major weed in annual cropping systems. For nearly a century, A. trifida has also been of great concern in the U.S. for its highly allergenic pollen, necessitating targeted control measures to reduce its impact on human populations. Based on the distribution of A. trifida in North America and in its introduced range, riparian systems in the rest of the world may be particularly at risk to invasion, with potential negative consequences for their biodiversity. Currently, A. trifida has invaded Asia more widely than Europe, likely due to the more favourable local conditions in Asia. Throughout its introduced range, A. trifida is host to a limited number of invertebrates and pathogens and only a few biological agents are available for its control. The main impacts of A. trifida at a global level are on crop yield and human health, resulting in significant socio-economic impacts. The success of A. trifida invasion in areas in which it has been introduced is still unclear, but climate change may increase climate suitability, increasing the potential for A. trifida to spread. While effective management in cultivated fields seems potentially possible, the development and control of A. trifida in natural riparian habitats is of great concern due to the difficulty of management in these areas.

Le débat sur le rôle des plantations forestières sur la protection des forêts naturelles et de la biodiversité associée est ancien et a pu faire l'objet de nombreuses controverses (Aubréville 1953). Cet article se propose d'y apporter sa contribution en prenant l'exemple de Madagascar.

Thousands of plant species have been introduced, intentionally and accidentally, to South Africa from many parts of the world. Alien plants are now conspicuous features of many South African landscapes and hundreds of species have naturalised (i.e. reproduce regularly without human intervention), many of which are also invasive (i.e. have spread over long distances). There is no comprehensive inventory of alien, naturalised, and invasive plants for South Africa, but 327 plant taxa, most of which are invasive, are listed in national legislation. We collated records of 759 plant taxa in 126 families and 418 genera that have naturalised in natural and semi-natural ecosystems. Over half of these naturalised taxa are trees or shrubs, just under a tenth are in the families Fabaceae (73 taxa) and Asteraceae (64); genera with the most species are Eucalyptus, Acacia, and Opuntia. The southern African Plant Invaders Atlas (SAPIA) provides the best data for assessing the extent of invasions at the national scale. SAPIA data show that naturalised plants occur in 83% of quarter-degree grid cells in the country. While SAPIA data highlight general distribution patterns (high alien plant species richness in areas with high native plant species richness and around the main human settlements), an accurate, repeatable method for estimating the area invaded by plants is lacking. Introductions and dissemination of alien plants over more than three centuries, and invasions over at least 120 years (and especially in the last 50 years) have shaped the distribution of alien plants in South Africa. Distribution patterns of naturalised and invasive plants define four ecologically-meaningful clusters or “alien plant species assemblage zones”, each with signature alien plant taxa for which trait-environment interactions can be postulated as strong determinants of success. Some widespread invasive taxa occur in high frequencies across multiple zones; these taxa occur mainly in riparian zones and other azonal habitats, or depend on human-mediated disturbance, which weakens or overcomes the factors that determine specificity to any biogeographical region.

Globalisation has resulted in the movement of organisms outside their natural range, often with negative ecological and economic consequences. As cities are hubs of anthropogenic activities, with both highly transformed and disturbed environments, these areas are often the first point of entry for alien species. We compiled a global database of cities with more than one million inhabitants that data had on alien species occurrence. We then identified the most prominent pathways of introduction and vectors of spread of alien species in these cities. Most species were intentionally introduced to cities and were released or escaped from confinement. The majority of alien species then spread within cities through natural means (primarily unaided dispersal). Pathway prominence varied across the taxonomic groups of alien species: the most prominent pathway for plants and vertebrates was the escape pathway; for invertebrates the stowaway and contaminant pathways were most likely to facilitate introductions. For some organisms, pathway prominence varied with the geographical and climatic characteristics of the city. The characteristics of the cities also influenced the prominence of vectors of spread for alien species. Preventing the natural spread of alien species within cities, and into adjacent natural environments will be, at best, difficult. To prevent invasions, both the intentional and unintentional introduction of potentially harmful alien species to cities must be prevented. The pathways of introduction and vectors of spread identified here should be prioritised for management.

Des observations récentes montrent que l’aire de répartition connue au Québec du saltique myrmécomorphe Synageles venator (Lucas, 1836) s’est étendue de près de 500 km vers l’est. La première mention de cette espèce en Amérique du Nord remonte à 1998. On l’avait observée dans la région de Montréal, où des récoltes subséquentes ont confirmé son établissement. Moins d’une dizaine d’années plus tard, on la signalait à Québec. Cet article décrit les premières observations du S. venator à l’est de la ville de Québec. En 2013 et en 2014, des spécimens mâles et femelles ont été trouvés dans une tourbière en restauration près de Rimouski, au Bas-Saint-Laurent. En 2016, de nouvelles récoltes ont été faites à deux endroits à Bonaventure, en Gaspésie. Ces données suggèrent que le S. venator est désormais largement répandu au Québec. Nous discutons des implications de cette extension d’aire de répartition., Recent observations extend the known distribution of the introduced ant-like jumping spider, myrmecomorph salticid Synageles venator (Lucas, 1836), in the province of Québec (Canada), eastwards by approximately 500 km. The first North American record of this species was from Montréal in 1998, and subsequent observations there confirmed its establishment. Then, less than ten years later, it was reported further east, in Québec City. The present article describes the first records in the province of S. venator east of this location. In 2013 and 2014, male and female specimens were collected in a restored peatland near Rimouski (Bas-Saint-Laurent region), and in 2016, further specimens were found at two locations in Bonaventure (Gaspésie region). Data suggest that S. venator is now widely distributed in the province. The implications of this range expansion are discussed.

Honey bees are the most economically important crop pollinator worldwide. They depend on a diversity of pollen for reproduction and colony growth. However, the influence of landscape composition on diversity and quantity of pollen collection by honey bees remains largely unexplored, particularly in variegated landscapes. Pollen on honey bees was trapped from 41 hives across ten sites in the Western Cape, South Africa during summer. Sampled hives were near eucalyptus trees surrounded by a high percentage of natural vegetation. Hives could therefore potentially be presented with a diverse range of flowers. To obtain a measure of relative abundance and representation of plant taxa pollen samples were collected at hives, sorted by color, weighed and DNA barcoded. Landscape analysis was performed to estimate the relative availability of the main floral resource-types and how this influenced the composition of pollen collected. Overall, eucalyptus made up the largest portion (∼49%) of pollen loads, the remainder was composed of 31 other taxa (12% native and 39% alien plants). An increase in the area of eucalyptus resulted in an increased as well as the relative amount of eucalyptus and natural pollen collected. Conversely, an increase in the area of eucalyptus resulted in a decrease in alien plant pollen and vice versa. Our results provide important quantitative evidence that shows the amount and diversity of pollen used by honey bees in summer appears to be disproportionately met by human-modified landscapes; whereas, natural vegetation, despite its large extent and diversity, performs a lower-level role during this season.

présentation orale; International audience

Spatio-temporal evolution of life history traits related to dispersal, Brown trout colonization of the sub-antarctic Kerguelen islands. Journées de l'Ecole Doctorale

De nombreux individus de l’hélice des bois (Arianta arbustorum) ont été observés à Boucherville en juin 2015 et en 2016 ainsi qu’à l’Île-des-Soeurs en juin 2016. Cela représente les premières mentions de cette espèce au Québec et surtout, celles de populations viables. En 2015, un petit-gris (Cornu aspersum) juvénile a également été trouvé dans une grappe de raisins de Californie qui provenait d’une épicerie de Sherbrooke. Ces deux espèces d’escargots exotiques sont originaires d’Europe. Elles ont été introduites ailleurs au Canada et ne semblent pas envahissantes. Cependant, un suivi serait nécessaire pour vérifier la survie à plus long terme des populations d’hélice des bois à Boucherville et à l’Île-des-Soeurs et valider la présence de cette espèce ailleurs au Québec., The present article provides information from Québec (Canada) concerning the record of two species of exotic snails native to Europe. In June 2015, numerous copse snails (Arianta arbustorum) were observed at Boucherville, and in June 2016, further specimens were found on Ile-des-Soeurs. These are the first records of this species for the province and are of viable populations. In 2015, a juvenile brown garden snail (Cornu aspersum) was found in a bunch of Californian grapes bought at a grocery store in Sherbrooke. Both these species have been introduced elsewhere in Canada, but do not seem to be invasive. Further surveys will, however, be needed to evaluate the persistence of the copse snail populations, and to evaluate the presence of the species elsewhere in the province.

Ajouter pagination et wos; International audience; The introduction of organisms within the native range of wild conspecifics is a widespread phenomenon and locally modifies patterns in intraspecific diversity. However, our knowledge of the resulting ecological effects, as opposed to those caused by invasion-induced changes in interspecific diversity, is still limited. Here, we investigated the ecological effects of native and non-native invaders across levels of biological organisations and recipient organisms using the global and long history introductions of salmonids. Our meta-analysis demonstrated that the global effects of native species introductions exceeded those induced by non-native invaders. The impacts of native invaders were primarily manifested at the individual level on wild conspecifics, but remained largely unexplored on other native organisms and at the community and ecosystem levels. Overlooked and poorly appreciated, quantifying the impacts of native invaders has important implications because human-assisted introductions of domesticated organisms are ubiquitous and likely to proliferate in the future.

International audience; Natural rubber is a strategic raw material in many sectors of modern industrial societies and is almost exclusively produced by cultivating rubber trees [Hevea brasiliensis (Willd. ex A. Juss.) Mull. Arg.)]. Breeding of this species focuses mainly on advanced improved varieties developed over a century in Southeast Asia and Africa, but it also relies on genetic diversity available in wild germplasm. In this study, we describe the diversity observed within 1060 accessions originating from the state of Rondonia (Brazil) and conserved ex situ in Vietnam. Available passport data for these accessions indicate their putative distribution throughout seven districts in Rondonia. Genotyping data obtained on these accessions with 15 SSR markers generated 458 different alleles. A principal coordinate analysis enabled a clear separation of accessions from Calama district on the first axis, as well as accessions from Ariquemes and Ji-Parana districts on opposite sides of the second axis. A three-step Bayesian analysis of population structure gave a clearer representation, involving three levels of differentiation. At the first differentiation level, the accessions were divided into two clusters, k1 comprising 42% of the accessions, k2 with 25%, and the remaining 33% being admixed accessions. Further levels of Bayesian analysis enabled to distinguish between accessions from different farms in a same district. A better knowledge of the genetic structure at the infra-Rondonia state level, will help in using this available genetic diversity in future breeding programs.

Marnotte Pascal,Le Bourgeois Thomas. Porophyllum ruderale (Jacq.) Cass.. In: Le Journal de botanique, n°87, 2019. pp. 123-125.

Host range evolution is a central issue for pest management, particularly for invasive species of agricultural importance. The invasive tomato leaf miner, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), a key pest of tomato in Europe and recently in sub-Saharan Africa, is a good model organism to better understand underlying processes. We studied oviposition acceptance (proportion of females accepting a given plant as host for laying egg), oviposition preference (number of eggs laid by females on a given host plant) and performance (offspring development estimated as survival from egg to adult) of two T. absoluta populations originating from France (FRA) and Senegal (SEN) on six solanaceous plants (tomato, eggplant, Ethiopian eggplant, potato, sweet pepper and pepper). The ovipositional behavioral pattern differed between the two populations; the SEN population showed higher oviposition acceptance on Ethiopian eggplant and sweet pepper than the FRA population. In addition, SEN population showed higher oviposition preference toward sweet pepper and potato than the FRA population. By contrast, the FRA population showed higher preference toward tomato and eggplant than the SEN population. The two populations of T. absoluta performed best on tomato (the preferred host plant) and showed similar decreasing trend in performance when comparing the two populations on the various other host plants. For both populations, performance on solanaceous plant species was closely related to ovipositional response of females to these plants. The differences observed between the two populations may indicate an ongoing differentiation in the host range of T. absoluta in the two invaded areas, possibly due to the abundance of these alternative host crops in Senegal at a period when tomato crops are scarce.

Correct estimation of interindividual variability is of primary importance in models aiming to quantify population dynamics. In a fisheries context, individual information such as age and growth is often extracted using scales; however, the rationale for using a given scalimetric method (i.e. number of scales per individual and number of readers) is rarely discussed, but different sources of variance may affect the results. As a case study, we used scale growth and age of brown trout (Salmo trutta) caught in the Kerguelen Islands. Based on a nested design (readings of four scales per fish by two independent readers), we decomposed variance in growth and age according to fish (interindividual level), scales (intraindividual level) and readers by using repeatability analysis. The results highlight that most variation is attributable to fish. Readers and scales contribute little to interindividual variance, suggesting that inference was insensitive to intraorganism biological variation. Using additional scales or readers was an inefficient use of sampling resources. We argue that variance decomposition should be widely used for studies aimed at modelling natural variability in life history traits. This would improve our knowledge of the implications of measurement error, helping rationalise and define appropriate sampling strategies.

International audience; We show distribution of the sea slug Dendrodoris limbata (Cuvier, 1804) (Mollusca, Gastropoda, Nudibranchia) along metropolitan French coasts. 82 records between 2010 and 2017 were extracted from the citizen science database BioObs. This species native to Mediterranean shows a discontinuous distribution, on one hand along Mediterranean coast from Var to Pyrénées-Orientales, mainly in Lagune de Thau; on the other hand in the Golfe Normand-Breton of the English Channel where it is introduced. We discuss the potential role of oyster transfer between shellfish ponds as a vector of this discontinuous distribution.; Nous présentons les données de répartition le long des côtes françaises métropolitaines de la Dorisfrangée Dendrodoris limbata (Cuvier, 1804) (Mollusca, Gastropoda, Nudibranchia) issues de la basede sciences participatives BioObs, entre 2010 et 2017. Cette espèce native de Méditerranée présenteune répartition discontinue, le long des côtes méditerranéennes du Var aux Pyrénées-Orientales d’unepart, et dans le golfe normand-breton où elle a été introduite d’autre part. La possible implication dutransport de coquillages comme vecteur de cette répartition discontinue est discutée.

International audience; In a context of global change, biological invasions are one of the main causes of biodiversity loss. Non-­native species can disperse naturally but the rate of dispersion has increased during the last decades through anthropogenic and natural introductions. In both cases, organisms can adapt or move to be resilient to the global warming, leading to the colonization of new habitat. The study of colonization is of major interest to manage appropriately their invasiveness, to understand their response to global warming and to conserve natural biodiversity.As a consequence of ice retreat in the highest latitude, newly opened rivers could become welcoming habitats for the establishment of colonizing fish. Thus, temperate species will be expected to move to higher latitudes. Salmonids are thought to be good candidates for colonizing such environments since they generally display intrinsic ability to become invasive.Because of its unique characteristics, invasion by the Brown trout (Salmo trutta L.) in sub-­Antarctic Kerguelen Islands represents a good model to improve our knowledge in fish population dynamics in a post­-glacial invasion context. This facultative anadromous iteroparous species shows various life history strategies patterns and is characterized by high phenotypic plasticity where migration plays a significant role in the spatial dynamics of populations. Introduced in the 1950s in a dozen freshwater systems originally deprived of any fish species, the species colonized more than thirty streams in only ten generations. Thanks to long­term monitoring, our data would shed light on the future of polar regions where,because of ice melting, fish­free ecosystems become increasingly accessible to invasion by fish species

International audience

International audience

International audience

International audience; Brown trout (Salmo trutta L.) was voluntarily introduced in some rivers of the Kerguelen Islands in the 1950s–1960s. Fish originating from hatcheries rapidly colonized other streams, thanks to the early occurrence of anadromous (i.e., migratory) form. Getting insight into the success of colonization requires investigating fitness-related traits such as growth and reproductive investment. In particular, increased growth and body size—traits that are broadly related to dispersal ability—are predicted on colonization front, to the possible detriment of reproductive ability. We here report such investigation on early data following the first natural reproductions in the founder populations of Kerguelen, from 1971 to 1994, assessing the main characteristic on growth at sea and reproductive investment for both sexes. Our results reveal that growth of sea trout is excellent with individuals fully benefiting from their relatively short period of growth at sea, sizes and weights ranking among the highest recorded to date. During the reproduction period, males lose on average 15–21% of their weight, whereas females lose 18–19% of their weight. Although a trade-off between growth and reproduction may arise at marginal distribution of invasive species, our study indicates that any potential advantages arising from increased growth and therefore potential dispersal ability may not be directly balanced by reduced reproductive investment, with respect to other published studies. Results overall shed light on intrinsic invasiveness of the brown trout in a post-glacial landscape with barely any interaction with human activities.

résumé; International audience

résumé; International audience

International audience; 1. The whitefly Bemisia tabaci is a worldwide pest considered to be a complex of cryptic species. Its identification is primarily based on mitochondrial COI sequences. Microsatellite markers can also be used to identify this species and to study its population structure. Moreover, B. tabaci species harbour quite specific endosymbiont communities that can constitute additional markers for identification. Previous studies have demonstrated the occurrence of two B. tabaci species on the island of La R\ₑunion: the exotic MEAM1 and the indigenous IO. A recent field survey revealed unusually high densities of whiteflies in Saint Pierre, and this could reflect the introduction of a new B. tabaci species. 2. To test the putative introduction of a new invasive species, B. tabaci individuals were collected at Saint Pierre and at six additional sites. Among these samples, analyses were conducted on mitochondrial COI, microsatellites, and endosymbiont communities. 3. Based on the mitochondrial COI marker, we detected in Saint Pierre two subgroups (Eastern and Western) characteristic of the invasive MED species. This is the first time these subgroups have been found in La R\ₑunion. The analysis of microsatellite data from the seven sites around the island showed that (i) the geographical distribution of MED seems confined to Saint Pierre, (ii) no hybrids were detected between MED individuals and the resident species, and (iii) the MED population, while exhibiting two mitochondrial haplotypes, has a homogenous nuclear genetic background. The two MED subgroups differing in their mitochondrial haplotype also specifically differed in their endosymbiotic diversity. (Résumé d'auteur)

The Mourning Gecko, Lepidodactylus lugubris, is an invasive parthenogenetic species first recorded on Guadeloupe in November 2010. Today it is widely distributed on the island, at least in the south of Grande-Terre and the northeast of Basse-Terre. It occurs in and around human habitations, often together with another invasive gecko, Hemidactylus mabouia. Other species of invasive geckos native to the Eastern Hemisphere have similar life histories and therefore are expected to become established in Guadeloupe in the future. The impact of these introduced species on the native biodiversity of the island is not yet clear.

International audience; Why do some species successfully invade new environments? Which of these invasive species will alter or even reshape their new environment? The answers to these questions are simultaneously critical and complex. They are critical because invasive species can spectacularly alter their new environment, leading to native species extinctions or loss of important ecosystem functions that fundamentally reduce environmental and societal services. They are complex because invasion success in a novel environment is influenced by various attributes embedded in natural landscapes—biogeographical landscape properties, abiotic environmental characteristics, and the relationship between the invasive species and the resident species present in the new environment. We explore whether a condensed record of the relationships among species, in the form of a network, contains the information needed to understand and predict invasive species success and subsequent impacts. Applying network theory to study invasive species is a relatively novel approach. For this reason, much research will be needed to incorporate existing ecological properties into a network framework and to identify which network features hold the information needed to understand and predict whether or not an invasive species is likely to establish or come to dominate a novel environment. This paper asks and begins to answer the 14 most important questions that biologists must address to integrate network analysis into the study of invasive species. Answering these questions can help ecologists produce a practical monitoring scheme to identify invasive species before they substantially alter native environments or to provide solutions to mitigate their harmful impacts.

International audience; In order to respond to the growing concern on invasive alien species and their impact in freshwater environments in France, a working group on biological invasions in freshwater environments was created in 2009. Meeting internationally recognised recommendations, its main objective is to increase management capacity by valuating and promoting expert knowledge, digesting and giving access to scientific information and providing guidance on decision-making. Coordinated by the French Biodiversity Agency and the IUCN French Committee, the group brings together more than 60 members from communities of practitioners, scientists and policy-makers. The group’s activities are determined by the shared needs of the formed network. Examples of projects undertaken to date include: the development of an internet platform to provide access to information; the publication of a best practices guide with fully detailed feedbacks from management efforts; and the setting up of an information database focussed on the operational management of introduced aquatic species in France

Science-based strategies to tackle biological invasions depend on recent, accurate, well-documented, standardized and openly accessible information on alien species. Currently and historically, biodiversity data are scattered in numerous disconnected data silos that lack interoperability. The situation is no different for alien species data, and this obstructs efficient retrieval, combination, and use of these kinds of information for research and policy-making. Standardization and interoperability are particularly important as many alien species related research and policy activities require pooling data. We describe seven ways that data on alien species can be made more accessible and useful, based on the results of a European Cooperation in Science and Technology (COST) workshop: (1) Create data management plans; (2) Increase interoperability of information sources; (3) Document data through metadata; (4) Format data using existing standards; (5) Adopt controlled vocabularies; (6) Increase data availability; and (7) Ensure long-term data preservation. We identify four properties specific and integral to alien species data (species status, introduction pathway, degree of establishment, and impact mechanism) that are either missing from existing data standards or lack a recommended controlled vocabulary. Improved access to accurate, real-time and historical data will repay the long-term investment in data management infrastructure, by providing more accurate, timely and realistic assessments and analyses. If we improve core biodiversity data standards by developing their relevance to alien species, it will allow the automation of common activities regarding data processing in support of environmental policy. Furthermore, we call for considerable effort to maintain, update, standardize, archive, and aggregate datasets, to ensure proper valorization of alien species data and information before they become obsolete or lost.

Pinus halepensis Mill. was introduced into regions with a Mediterranean cli- mate as an ornamental tree, and is now often found in parks and gardens. At pre- sent, Aleppo pine (Pinus halepensis Mill.) forests cover approximately 2,500,000 ha in the Mediterranean Basin, mostly at low altitudes (less than 500 m) and along the coast. It has become naturalized outside cities in North Africa to the extent that it is now listed as an invasive species there. Because of its size (over 15 m in height and 30 cm in diameter), Pinus hale- pensis could be a good potential green resource for structural material in Tunisia. The focus of this study was to assess rot resistance and the physical and mecha- nical properties of reforestation Aleppo pine from the Mediterranean basin. The Pinus halepensis wood samples studied were collected from 6 tree provenances in Tunisia for physical and mechanical characterization and from Morocco for decay and termite resistance tests. Den- sities and shrinkage were determined and mechanical and rot resistance tests performed. Preliminary results showed that Tunisian Pinus halepensis wood has great dimensional stability. Although the compressive strength of Pinus halepen- sis wood is high, its bending strength is rather low for each of the provenances. MOR in bending is lower than in other Tunisian softwood species. Finally, Pinus halepensis sapwood has low resistance to fungi and termites. This timber species could be valuable for furniture and/or as a building material provided that a wood preservation method is applied before it is used.

Alien species can have major ecological and socioeconomic impacts in their novel ranges and so effective management actions are needed. However, management can be contentious and create conflicts, especially when stakeholders who benefit from alien species are different from those who incur costs. Such conflicts of interests mean that management strategies can often not be implemented. There is, therefore, increasing interest in engaging stakeholders affected by alien species or by their management. Through a facilitated workshop and consultation process including academics and managers working on a variety of organisms and in different areas (urban and rural) and ecosystems (terrestrial and aquatic), we developed a framework for engaging stakeholders in the management of alien species. The proposed framework for stakeholder engagement consists of 12 steps: (1) identify stakeholders; (2) select key stakeholders for engagement; (3) explore key stakeholders' perceptions and develop initial aims for management; (4) engage key stakeholders in the development of a draft management strategy; (5) re-explore key stakeholders' perceptions and revise the aims of the strategy; (6) co-design general aims, management objectives and time frames with key stakeholders; (7) co-design a management strategy; (8) facilitate stakeholders' ownership of the strategy and adapt as required; and (9) implement the strategy and monitor management actions to evaluate the need for additional or future actions. In case additional management is needed after these actions take place, some extra steps should be taken: (10) identify any new stakeholders, benefits, and costs; (11) monitor engagement; and (12) revise management strategy. Overall, we believe that our framework provides an effective approach to minimize the impact of conflicts created by alien species management.

International audience; L'introduction d'essences exotiques en forêt a des implications plus ou moins importantes sur la biodiversité selon le contexte écologique concerné. Un boisement en zone fortement rudéralisée aura un effet positif sur la biodiversité forestière, mais si cette introduction se fait au détriment d’une zone naturelle abritant des espèces à haute valeur patrimoniale, ce boisement aura un effet négatif sur la biodiversité globale. Dans le contexte de changement climatique, il est envisagé un remplacement d’essence autochtone par des essences exotiques pour garantir une meilleure survie des arbres. Cela devrait se traduire par une perte de biodiversité associée en l’absence de période de coévolution entre ces nouvelles essences et la biodiversité autochtone qui leur sera pour partie inadaptée. Les espèces d’arbres invasives sont à proscrire car elles sont capables de s’échapper des zones de plantations pour s’étendre sur des zones naturelles à haute valeur patrimoniale entrainant, du fait de leur forte capacité de reproduction et de compétition une perte de biodiversité globale. Malgré les nombreuses publications scientifiques sur ce thème, les résultats sont souvent exprimés en termes de richesse spécifique et prennent rarement en compte la valeur patrimoniale des espèces, ce qui ne permet pas d’avoir une idée précise des impacts sur la biodiversité. De plus un bilan est nécessaire à l’échelle européenne pour connaitre la biodiversité associée à chaque essence avant de pouvoir apprécier correctement la perte qu’engendrerait le remplacement des essences autochtones par des essences introduites.

Une synthèse des connaissances relatives aux caractéristiques des peuplements animaux et végétaux de la Nouvelle-Calédonie met en évidence leur exceptionnelle richesse spécifique et leur fort taux d’endémisme. Une originalité supplémentaire caractérise ces peuplements : le micro-endémisme manifesté par la majorité de leurs espèces. Ce micro-endémisme rend particulièrement vulnérable la biodiversité néo-calédonienne aux agressions et tout particulièrement à celles d’origine anthropique : exploitation des ressources vivantes, destruction et fragmentation des habitats et introductions d’espèces. Une synthèse de l’impact préhistorique et historique de ces agressions est présentée et aboutit au constat d’un spectaculaire accroissement de ces impacts au cours du xxe siècle en rapport, direct ou non, avec l’activité minière. Cette situation va se détériorer avec le développement des importants programmes miniers en cours, ce qui conduit à conclure que de nombreuses espèces endémiques dont l’aire de répartition et l’effectif des populations sont déjà considérablement réduits vont s’éteindre. Face à l’urgence de la situation, ce risque d’extinction massif est évalué et des propositions sont avancées en vue de l’éviter ou, au moins, de le limiter. A synthetic review of our understanding of significant faunal and floral communities pointed New Caledonia as having a unique rich biodiversity with a very high level of endemism. Another characteristic of New Caledonia’s biodiversity is the tiny distribution area of its endemic species. This micro-endemism makes New Caledonia’s biodiversity particularly vulnerable to anthropogenic effects such as exploitation of natural resources, mining and development, which already lead to the destruction and fragmentation of habitats and the introduction of alien species. An overview of the prehistoric and historic anthropic impact on the island’s environment shows a drastic increase of constraints during the xxth century. Much of the damage was linked to mining activities but other ones such as logging have also contributed to the loss of biodiversity. Several new giant mining operations, underway or planned, dramatically increase the species extinction’s risk in the already fragile floral and faunal communities. Given the urgency of the situation, scientific evaluations of the risks of extinctions are given and propositions submitted in order to measure their progress and prevent or, at least, limit them.

Pour les chercheurs en biologie, les légumineuses arborées présentent de nombreuses qualités pour l'agronomie, en particulier la capacité à fixer l'azote atmosphérique. Celle-ci permet la production de parties végétales riches en matière azotée qui, lorsqu'elles se décomposent dans le sol, sont supposées en améliorer la " fertilité ". D'autre part, on met souvent en avant leur " richesse " pour la nutrition des hommes et des animaux et la qualité de leur bois. Les spécialistes du reboisement soulignent leur capacité de multiplication sexuée et végétative ainsi que leur aptitude à se développer en milieu peu fertile et ouvert. Les agro-sylvo-pastoralistes travaillant en terrains tropicaux constatent bien ces vérités scientifiques, parfois devenues de véritables paradigmes, mais en éprouvent au quotidien les limites. Il est bien connu que toutes les légumineuses ne fixent pas l'azote et aussi que cette fixation dépend des espèces, de leur association rhizobienne et des conditions environnementales, mais ceci n'est pas toujours dit dans les messages destinés à la " vulgarisation ". Si des transferts " directs " d'azote entre plantes ont été mis en évidence, l'importance du transfert d'azote et d'autres nutriments au bénéfice de plantes associées ou en rotation dépend du recyclage des organes des plantes fixatrices. A l'inverse, la récolte de leurs bois, fruits ou feuilles, peut aboutir à un appauvrissement de la fertilité du sol qui les porte. Leur formidable capacité à se multiplier et à s'ancrer durablement dans un milieu, en particulier lorsqu'il est dégradé, a aussi son " revers de médaille ", à savoir qu'elles peuvent souvent devenir envahissantes. Par ailleurs, les écologistes dogmatiques regretteront que des légumineuses provenant d'autres continents soient maintenant présentes dans la plupart des forêts. D'autres, plus pragmatiques, y verront l'émergence de " forêts nouvelles " dont il faut étudier l'écosystème mais aussi valoriser les biens et services, comme le font souvent les paysans. Il reste cependant que ces légumineuses arborées occupent une place de choix dans la palette des possibilités disponibles pour le praticien en charge de la restauration de milieux dégradés ou de la création de systèmes agro-sylvo-pastoraux productifs et résilients face aux changements globaux, à condition de manier avec prudence la lancinante tentation de l'introduction de la " plante miracle " qui peut parfois, si on n'y prend pas garde, devenir une " plante cauchemar ".