Use of forest fragments by animalivorous bats in french Guiana

The effects of habitat fragmentation on animalivorous bats were studied on recent forest islands created in 1994, at the time of the filling of Petit Saut dam in French Guiana. A sampling strategy, including control sites located in a nearby forested area not fragmented during the who le study period (1993-1997) was designed. Modifications affecting animali vorous bat communities in a remote 28 ha island (island 2) and in 15 islets smaller than 6 ha more or less isolated from the nearby continuous forest were analysed. Results were compared to those obtained with the same methods for frugivorous and nectarivorous bats. One hundred and forty eight gleaning animalivores, 41 aerial insectivores and 28 bats belonging to other guilds (omnivore, sanguivore) were trapped during the whole study. Capture analyses showed that species richness and abundance sharply declined in islets and in the island 2 in 1995 and 1996. However no significant difference was found between islands and continuous forest in 1997. There was no difference either in species richness or in abundance between the island 2 and several islets of comparable isolation. On the contrary, indices were significantly lower in far islets situated at more than 1 50 rn from the continuous forest than in near ones. One possible explanation is the reluctance of understorey species to cross open water to reach far islands. Between 1994 and 1997, we failed to detect any difference in the relative proportion of aerial insectivores and gleaning animalivores between islands and the continuous forest. Among non-frugivorous species, gleaning animalivores represented 73 % of the total number of captures made in the two habitats. Similarly no habitat differences were found in the respective contributions of frugivores and animalivores to bat communities. Frugivores made up roughly 80 % of the total number of bats captured during the study. Within the gleaning animalivores guild, there was a positive relationship between abundance of a species in islands and its abundance in the control area. Moreover, a positive correlation was equally found between body size and abundance in all habitats. The contribution of our results to the understanding of the impact of habitat fragmentation on animalivorous bats is limited due to rarity and low detectability of a high number of species making up animalivorous bat communities in Neotropical forests. Therefore, additional methods to collect and analyse data that take into account these features should be implemented to evaluate more accurately the impact of habitat fragmentation on bat communities at Saint-EugèneLes effets de la fragmentation de l'habitat sur la communauté des chauves-souris animalivores ont été étudiés dans les îlots forestiers formés en 1994 lors de la mise en eau du barrage de Petit Saut (Guyane française). Un protocole d'échantillonnage standardisé, incluant une zone de référence restée intacte tout au long de l'étude entre 1993 et 1997, a permis de suivre les modifications affectant la communauté des chauves-souris animalivores dans une île de 28 ha (île 2) bien isolée et dans 1 5 îlots d'une superficie inférieure à 6 ha plus ou moins isolés selon les cas. Les résultats obtenus ont été comparés avec ceux obtenus dans les mêmes conditions lors d'une précédente étude pour les chauves-souris frugivores et nectarivores. 148 chauves-souris animalivores glaneuses, 41 insectivores aériennes, 28 omnivores ou hématophages ont été capturées au cours de l'étude. L'analyse de ces captures montre que la richesse spécifique et l'abondance des individus ont chuté fortement en 1995 et 1996 dans l'île 2 et dans les îlots mais pas en 1997. Aucune différence de richesse ou d'abondance entre l'île 2 et les îlots de degré d'isolement comparable n'a été détectée. En revanche, les indices de richesse et d'abondance obtenus pour les îlots éloignés de plus de 150 m du bloc forestier sont significativement plus faibles que ceux obtenus pour les îlots situés à proximité immédiate de la forêt intacte. Il est suggéré que le survol d'une étendue d'eau libre pourrait constituer une barrière au déplacement notamment pour les espèces animalivores glaneuses de sous-bois. Entre 1994 et 1997, la proportion relative de chauves-souris aériennes insectivores et glaneuses animalivores dans les îlots forestiers et dans le bloc forestier n'était pas différente, les glaneuses animalivores représentant 73 % des captures dans les deux milieux. De même, il n'y a pas de différence dans la contribution respective des guildes animalivores et frugivores aux peuplements insulaire et du bloc forestier. Les chauves-souris frugivores représentent autour de 80 % des captures dans les deux habitats. A l'intérieur de la guilde des glaneuses animalivores, il existe une forte corrélation entre l'abondance d'une espèce en forêt non perturbée et son abondance dans l'île 2 et dans les îlots. Une corrélation positive entre la taille corporelle et l'abondance a également été trouvée tous milieux confondus. La portée des résultats obtenus ici est limitée du fait de la rareté et de la faible piégeabilité d'un nombre élevé d'espèces qui composent le peuplement des chauves-souris animalivores en forêt néotropicale. D'autres techniques de collecte et d'analyse des données, qui tiennent compte de ces particularités, devront être mises en oeuvre pour pleinement évaluer l'impact de la fragmentation de l'habitat sur les communautés de chauves-souris animalivores à Saint-Eugèn

Intégration de fonctions topologiques du paysage dans le calcul des distances-coût

ACLInternational audienceDistance is a basic concept in the issue of animal species motion. Cost distances are more and more used, in order to measure a realistic distance, by means of resistance values given for each landscape types. Here, we propose a method to compute resistance values by using 'topological functions of landscape', i. e. by taking account of proximity to habitat/ non habitat edges. We used a data set concerning the spreading of the fossorial water vole outbreak in the Franche-Comté region, and we tested several functions. The results show that statistical correlations clearly increase in comparison with usual cost-distances.La distance est une notion fondamentale dans les problématiques de déplacement des espèces animales. Pour représenter des distances de façon plus réaliste, les distances-coût sont de plus en plus utilisées à partir de valeurs de résistance affectées aux catégories de paysage. Nous proposons une méthode pour calculer les résistances en tenant compte de la proximité aux lisières entre habitat et non habitat, sous l'expression de " fonction topologique du paysage ". Après la présentation des données d'application concernant la propagation des pullulations de campagnols terrestre en Franche-Comté, plusieurs fonctions sont proposées. Les résultats montrent une corrélation nettement améliorée par rapport aux distances-coût usuelles

A 454 multiplex sequencing method for rapid and reliable genotyping of highly polymorphic genes in large-scale studies

Background: High-throughput sequencing technologies offer new perspectives for biomedical, agronomical and evolutionary research. Promising progresses now concern the application of these technologies to large-scale studies of genetic variation. Such studies require the genotyping of high numbers of samples. This is theoretically possible using 454 pyrosequencing, which generates billions of base pairs of sequence data. However several challenges arise: first in the attribution of each read produced to its original sample, and second, in bioinformatic analyses to distinguish true from artifactual sequence variation. This pilot study proposes a new application for the 454 GS FLX platform, allowing the individual genotyping of thousands of samples in one run. A probabilistic model has been developed to demonstrate the reliability of this method. Results: DNA amplicons from 1,710 rodent samples were individually barcoded using a combination of tags located in forward and reverse primers. Amplicons consisted in 222 bp fragments corresponding to DRB exon 2, a highly polymorphic gene in mammals. A total of 221,789 reads were obtained, of which 153,349 were finally assigned to original samples. Rules based on a probabilistic model and a four-step procedure, were developed to validate sequences and provide a confidence level for each genotype. The method gave promising results, with the genotyping of DRB exon 2 sequences for 1,407 samples from 24 different rodent species and the sequencing of 392 variants in one half of a 454 run. Using replicates, we estimated that the reproducibility of genotyping reached 95%. Conclusions: This new approach is a promising alternative to classical methods involving electrophoresis-based techniques for variant separation and cloning-sequencing for sequence determination. The 454 system is less costly and time consuming and may enhance the reliability of genotypes obtained when high numbers of samples are studied. It opens up new perspectives for the study of evolutionary and functional genetics of highly polymorphic genes like major histocompatibility complex genes in vertebrates or loci regulating self-compatibility in plants. Important applications in biomedical research will include the detection of individual variation in disease susceptibility. Similarly, agronomy will benefit from this approach, through the study of genes implicated in productivity or disease susceptibility trait

Protocols for field and laboratory rodent studies

http://www.ceropath.org/references/rodent_protocols_bookTechnical book"Protocols for field and laboratory rodent studies" present the best practices for the studies of rodents and rodent-borne pathogens and parasites from the field to the laboratory. It aims at covering the different steps of rodent studies: 1) Trapping, 2) Dissection and preparation of tissue samples for pathogens screening, 3) Identification of species, 4) Isolation of helminths, 5) Preparing rodent specimens for collections. This book gathers accurate recommendations and techniques, based on those generally accepted in the literature and adapted from the experience of the different authors during rodent surveys and laboratory work. Its presentation is designed to work in the fields with a clear and colorful organization of each chapter, with: inserts providing definitions and recommendations, protocols detailed step by step, and an emphasis on illustrations with several photographs. This book is a publication generated by the CERoPath project (Community Ecology of Rodents and their Pathogens in a changing environment, www.ceropath.org) funded by the French Ministry of Research from 2008 to 2011

No Difference between the Sexes in Fine-Scale Spatial Genetic Structure of Roe Deer

Background: Data on spatial genetic patterns may provide information about the ecological and behavioural mechanisms underlying population structure. Indeed, social organization and dispersal patterns of species may be reflected by the pattern of genetic structure within a population. [br/] Methodology/Principal Findings: We investigated the fine-scale spatial genetic structure of a roe deer (Capreolus capreolus) population in Trois-Fontaines (France) using 12 microsatellite loci. The roe deer is weakly polygynous and highly sedentary, and can form matrilineal clans. We show that relatedness among individuals was negatively correlated with geographic distance, indicating that spatially proximate individuals are also genetically close. More unusually for a large mammalian herbivore, the link between relatedness and distance did not differ between the sexes, which is consistent with the lack of sex-biased dispersal and the weakly polygynous mating system of roe deer. [br/] Conclusions/Significance: Our results contrast with previous reports on highly polygynous species with male-biased dispersal, such as red deer, where local genetic structure was detected in females only. This divergence between species highlights the importance of socio-spatial organization in determining local genetic structure of vertebrate populations

Phylogeography of Puumala orthohantavirus in Europe

Puumala virus is an RNA virus hosted by the bank vole (Myodes glareolus) and is today present in most European countries. Whilst it is generally accepted that hantaviruses have been tightly co-evolving with their hosts, Puumala virus (PUUV) evolutionary history is still controversial and so far has not been studied at the whole European level. This study attempts to reconstruct the phylogeographical spread of modern PUUV throughout Europe during the last postglacial period in the light of an upgraded dataset of complete PUUV small (S) segment sequences and by using most recent computational approaches. Taking advantage of the knowledge on the past migrations of its host, we identified at least three potential independent dispersal routes of PUUV during postglacial recolonization of Europe by the bank vole. From the Alpe-Adrian region (Balkan, Austria, and Hungary) to Western European countries (Germany, France, Belgium, and Netherland), and South Scandinavia. From the vicinity of Carpathian Mountains to the Baltic countries and to Poland, Russia, and Finland. The dissemination towards Denmark and North Scandinavia is more hypothetical and probably involved several independent streams from south and north Fennoscandia

Phylogeography of Puumala orthohantavirus in Europe

Puumala virus is an RNA virus hosted by the bank vole (Myodes glareolus) and is today present in most European countries. Whilst it is generally accepted that hantaviruses have been tightly co-evolving with their hosts, Puumala virus (PUUV) evolutionary history is still controversial and so far has not been studied at the whole European level. This study attempts to reconstruct the phylogeographical spread of modern PUUV throughout Europe during the last postglacial period in the light of an upgraded dataset of complete PUUV small (S) segment sequences and by using most recent computational approaches. Taking advantage of the knowledge on the past migrations of its host, we identified at least three potential independent dispersal routes of PUUV during postglacial recolonization of Europe by the bank vole. From the Alpe-Adrian region (Balkan, Austria, and Hungary) to Western European countries (Germany, France, Belgium, and Netherland), and South Scandinavia. From the vicinity of Carpathian Mountains to the Baltic countries and to Poland, Russia, and Finland. The dissemination towards Denmark and North Scandinavia is more hypothetical and probably involved several independent streams from south and north Fennoscandia

En quoi l'étude des îlots forestiers permet-elle de mieux connaître le fonctionnement de la forêt tropicale ?

Small forested islands isolated from surrounding tropical forest by new reservoirs provide a norm for interpreting the effects of fragmentating the forest by intervening agriculture and pasture, and an effective means of investigating the ecological organization of the mainland forest. Water is a more effective barrier to immigration and a more neutral matrix than field or pasture. On forest fragments isolated by water, the effects of fragmentation are minimally confounded with effects of the matrix, while forest fragments surrounded by fields and pastures may suffer intrusions from tire, domestic animals, and other pests. On small islands, some species will go extinct. If the extinction of a species is followed by increase in its prey or competitors, we may provisionally assume that on the mainland, these prey and competitors are lirnited by the species now absent from the island. If, when a tree's seed disperser disappears, new seedlings of that tree no longer appear, that tree's regeneration presumably depends on its seed disperser. Islands in new reservoirs are the tropical forest ecologist's closest analogue to the exclusion experiments so effective in understanding the ecology of intertidal comrnunities. Small islands in reservoirs can also serve as systems of replicates for experimental analysis of the causes of regulation of selected populations. We review work on small islands isolated in 1914 by Panama's Gatun Lake, islands isolated in 1986 by Venezuela's Lake Guri, and islets isolated in 1994 at Saint-Eugène in French Guiana. The more recently the islands have been isolated, the more can be Jeamed from them. The Saint-Eugène Fragmentation Project is particularly important because it is only one of the three in true rainforest and studies there have been done before and after fragmentationLes petites îles boisées qui sont isolées de la forêt tropicale voisine après la mise en eau de réservoirs en amont des barrages hydroélectriques constituent des modèles pour l'étude de la fragmentation forestière après mise en agriculture ou pâturage. Elles offrent ainsi aux écologistes un protocole expérimental pour l'étude des processus écologiques de la forêt de terre ferme. L'eau est une barrière plus efficace et joue un rôle plus neutre contre l'immigration que les champs ou les pâturages. Sur des fragments forestiers isolés par une matrice aquatique, les effets de la matrice, qui sont souvent confondus avec ceux de la fragmentation, sont ici minimaux, alors que des fragments forestiers entourés de champs et de pâturages ont à supporter les feux intrusifs et l'invasion des animaux domestiques et autres pestes. Sur les petites îles, quelques espèces vont disparaître. Si l'extinction d'une espèce y est suivie de l'augmentation de la population de ses proies ou d'autres espèces compétitrices, on peut provisoirement supposer que, sur le continent, ces proies et compétiteurs sont limités par cette espèce qui a aujourd'hui disparu sur l'île. Si, lorsque l'agent disséminateur des graines d'un arbre disparaît et que les jeunes plantules de cet arbre ne sont plus présentes, c'est que la régénération de l'arbre en était fortement dépendante. Les îles des récents réservoirs sont, pour les écologistes, des systèmes expérimentaux analogues aux expériences d'exclusion qui sont si utiles pour comprendre l'écologie des communautés, des zones intertidales en particulier. Les îlots des réservoirs peuvent également servir comme système de réplicats pour l'analyse des causes de la régulation de certaines populations. Dans cet article, nous présentons une revue des études menées sur les petites îles isolées en 1914 par les eaux du lac Gatun au Panama, les îles isolées en 1986 par le lac Guri au Vénézuela, et les îlots formés en 1994 à Saint-Eugène en Guyane française. Plus les îles se sont formées récemment, plus les enseignements qui en découlent sont riches. Le Projet Fragmentation de Saint-Eugène est particulièrement important car c'est le seul des trois sites cités a être réalisé dans une vraie forêt tropicale humide, et les études y ont été menées avant et après la fragmentatio