Dans un contexte en constante évolution, l’élaboration, la mise en œuvre et l’évaluation des politiques publiques de biodiversité nécessitent d’anticiper les changements futurs possibles afin de pouvoir se préparer à temps. Or les informations concernant ces changements sont nombreuses et les enjeux qui pourraient s’avérer importants à l’avenir sont souvent peu visibles. Pour répondre à ce défi, une expertise multiacteurs et multidisciplinaire s’inspirant des démarches d’horizon scanning et intitulée BioPIQuE 2013 a permis d’identifier 25 questions émergentes, dont 10 questions stratégiques, pour les politiques publiques de biodiversité en France métropolitaine d’ici à 2020. Ces questions émergentes sont autant d’opportunités et de risques que l’ensemble des acteurs qui souhaitent avancer vers une plus grande prise en compte des enjeux de biodiversité peuvent saisir.

La recherche en biodiversite doit aujourd'hui repondre a des enjeux majeurs et renouveles. Ce texte de prospective part du constat que la perception des questions concernant la biodiversite a beaucoup change durant les dernieres annees : c'est maintenant un enjeu de la plus grande importance a l'echelle mondial tant au niveau scientifique et technique que politique, social et economique. La biodiversite apparait comme un des piliers du developpement durable et la notion de sa protection est desormais associee a celle de sa gestion et sa valorisation. En effet, la biodiversite peut etre consideree comme une ressource naturelle dont le mode de gestion fait qu'elle est ou non renouvelable. Il est admis desormais que la dynamique des changements globaux et de la mondialisation a une incidence majeure sur celle de la biodiversite ; il convient donc de comprendre les mecanismes de forcage de cette dynamique pour tenter de la reguler. Le present document identifie 9 points principaux qu'il est imperatif de prendre en compte pour developper une perspective scientifique qui s'appuie sur les avancees et le dynamisme de la recherche tout en etant en phase avec les attentes d'une societe inquiete de son avenir et du devenir de la planete. (Resume d'auteur)

Vous en êtes le directeur, pouvez-vous d'abord nous retracer les conditions de cette création, les motivations qui y ont présidé et la démarche de réflexion qui vous a amené à retenir l'intitulé EDD ?

Nine sites were sampled 19 times over 2 years in an irrigation system in Morocco in order to study species abundance in a snail community in relation to environmental parameters (including human activities) and migration (geographic distance) among sites. Each site was made of a sink and the first meters of the downstream canal. The snail community included four species (Bulinus truncatus, Lymnaea truncatula, Mercuria similis and Physa acuta). Strong spatial variation in species occurrence and abundance was detected which might be partly due to variation in water availability. However abundance in sinks and canals in which water availability differs were correlated. There was, as predicted, limited evidence in favor of isolation by distance which might be due to fast water current. Dispersal might therefore be an important factor structuring this community. On the other hand, the temporal variation was much more limited. This is consistent with the analysis of individual size distributions in B. truncatus, since no clear-cut cohorts were detected. The environmental parameters recorded (e.g. temperature, occurrence of macrophytes or cleaning of sinks) were extremely variable in time and space, except temperature. Analyzing their association with species through multidimensional methods indicated that P. acuta is ubiquitous and B. truncatus positively associated with macrophytes. These two species were associated in sinks. Less clear trends were detected for the two other species. Annual cleaning of sinks affected all species, but population recovery was fast in B. truncatus and P. acuta.

Correlations between allozyme heterozygosity and fitness-related traits, especially growth, have been documented in natural populations of marine bivalves. However, no consistent pattern has been exhib-ited, because heterotic effects on size vary with age and individual growth parameters are generally unknown. No consensus has emerged on the genetic basis of allozyme-associated heterosis. The species studied here, Spisula ovalis, displays annual shell growth lines, which allows us to compute individual age and growth dynamics over the whole life span. Our morphological study was coupled to a protein electrophoresis study at seven polymorphic loci. While the maximum size gained is not related to heterozygosity, the age at half maximum size, tIl2, is significantly negatively correlated with heterozygosity, indicating an heterotic effect on initial growth. The correlation between heterozygosity and size is expected to vanish when age increases, due to the form of the growth function. This decreasing correlation is consistent with previous studies. We compare the relative performances of five linear models to analyze the genetic basis of heterosis. Surprisingly, the largest part of variance in tIl2 is due to additive effects, the overdominant components being much weaker. Heterosis is therefore due to general genomic effects rather than to local overdominance restricted to allozymes or small neighboring chromosomal segments. A significant dependence of individual heterotic contributions of the enzyme loci upon expected heterozygosities, rather than metabolic function, further supports the hypothesis of enzymes acting as markers. General genomic effects can hold only if allozyme heterozygosity is positively correlated with heterozygosity at fitness-related genes scattered throughout the genome. This hypothesis is sup ported here by heterozygosity correlations between enzymatic loci.

Theoretical models have shown that when susceptibility to a parasite is genetically determined, polymorphism with regard to susceptibility can only be maintained by costs associated with resistance. However, an apparent resistance, or nonsusceptibility, may result from a lack of adaptation of the parasite, which does not imply any costs for the host. In this study, we analysed whether susceptibility was genetically determined in the Biomphalaria glabrata/Echinostoma caproni system, and we investigated the existence of costs associated with nonsusceptibility. Results showed that nonsusceptibility of B. glabrata to E. caproni was genetically determined and could be strongly selected for through generations. Furthermore, analysis of age at maturity among offspring segregating for susceptibility revealed that nonsusceptible individuals reached maturity later than susceptible ones. The delay in maturity is statistically significant and reflects a cost associated with resistance.

Samples of the bivalve Ruditapes decussatus collected in the lagoon of Thau (France, Mediterranean) after a period of natural anoxia (“malaïgue”) that caused significant mortality were compared to other samples that had not experienced anoxia. Survival to malaïgue was positively related to both shell length and heterozygosity at seven putative enzyme loci. Heterozygosity at locus Pgm-l was significantly higher in the sample of survivors than in the control; this was also observed in a sample of individuals monitored over a malaïgue induced in artificial conditions. These results suggest that heterozygosity at locus Pgm-l could be directly involved in determining the physiological mechanism of resistance to anoxic stress, but a genetic explanation involving the role of gametic disequilibrium is also discussed.

Freshwater snails have attracted the attention of biologists for a long time, because they are intermediate hosts of schistosomes, agents of bilharziases. However, population-genetic studies of freshwater snails have been undertaken only during the past decade, covering topics such as the relative roles of genetic drift and gene flow in subdivided populations and the roles of extinction and recolonization events in determining population structure. Other studies in freshwater snails have investigated the maintenance of sex and the evolution of selling, widening a debate restricted mainly to plant populations. The possible role of parasites in freshwater-snail population genetics has also been investigated.