253 research outputs found
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-EugÚneLes effets de la fragmentation de l'habitat sur la communauté des chauves-souris
animalivores ont été étudiés dans les ßlots 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 ßle de 28 ha (ßle 2) bien isolée et dans 1 5 ßlots 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 mĂȘmes conditions lors d'une prĂ©cĂ©dente Ă©tude 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'ßle 2 et dans les ßlots mais pas en 1997. Aucune différence de richesse ou d'abondance entre
l'ßle 2 et les ßlots de degré d'isolement comparable n'a été détectée. En revanche, les indices
de richesse et d'abondance obtenus pour les ßlots éloignés de plus de 150 m du bloc forestier
sont significativement plus faibles que ceux obtenus pour les ßlots situés à proximité
immĂ©diate de la forĂȘt intacte. Il est suggĂ©rĂ© que le survol d'une Ă©tendue d'eau libre pourrait
constituer une barriÚre au déplacement notamment pour les espÚces animalivores glaneuses
de sous-bois.
Entre 1994 et 1997, la proportion relative de chauves-souris aériennes insectivores et
glaneuses animalivores dans les ßlots forestiers et dans le bloc forestier n'était pas différente,
les glaneuses animalivores reprĂ©sentant 73 % des captures dans les deux milieux. De mĂȘme,
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 corrĂ©lation entre l'abondance d'une espĂšce en forĂȘt
non perturbée et son abondance dans l'ßle 2 et dans les ßlots. 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'espÚces qui composent le peuplement des chauves-souris
animalivores en forĂȘt nĂ©otropicale. D'autres techniques de collecte et d'analyse des donnĂ©es,
qui tiennent compte de ces particularitĂ©s, devront ĂȘtre mises en oeuvre pour pleinement
évaluer l'impact de la fragmentation de l'habitat sur les communautés de chauves-souris
animalivores Ă Saint-EugĂšn
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 espÚces 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 lisiÚres entre habitat et non habitat, sous l'expression de " fonction topologique du paysage ". AprÚs 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'Ă©tude des Ăźlots forestiers permet-elle de mieux connaĂźtre le fonctionnement de la forĂȘt 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-EugĂšne
in French Guiana. The more recently the islands have been isolated, the more can be Jeamed
from them. The Saint-EugĂšne 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 Ăźles boisĂ©es qui sont isolĂ©es de la forĂȘt tropicale voisine aprĂšs la mise en eau
de réservoirs en amont des barrages hydroélectriques constituent des modÚles pour l'étude de la fragmentation forestiÚre aprÚs mise en agriculture ou pùturage. Elles offrent ainsi aux
Ă©cologistes un protocole expĂ©rimental pour l'Ă©tude des processus Ă©cologiques de la forĂȘt de
terre ferme. L'eau est une barriĂšre plus efficace et joue un rĂŽle plus neutre contre
l'immigration que les champs ou les pùturages. 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 pĂąturages ont Ă supporter les feux intrusifs et l'invasion des animaux domestiques et autres
pestes. Sur les petites Ăźles, quelques espĂšces vont disparaĂźtre. Si l'extinction d'une espĂšce y
est suivie de l'augmentation de la population de ses proies ou d'autres espÚces compétitrices,
on peut provisoirement supposer que, sur le continent, ces proies et compétiteurs sont limités
par cette espÚce qui a aujourd'hui disparu sur l'ßle. Si, lorsque l'agent disséminateur des
graines d'un arbre disparaßt 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 ßles des récents
réservoirs sont, pour les écologistes, des systÚmes expérimentaux analogues aux expériences
d'exclusion qui sont si utiles pour comprendre l'écologie des communautés, des zones
intertidales en particulier. Les ßlots des réservoirs peuvent également servir comme systÚme
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 ßles isolées en 1914 par
les eaux du lac Gatun au Panama, les ßles isolées en 1986 par le lac Guri au Vénézuela, et les
ßlots formés en 1994 à Saint-EugÚne en Guyane française. Plus les ßles se sont formées
récemment, plus les enseignements qui en découlent sont riches. Le Projet Fragmentation de
Saint-EugĂšne est particuliĂšrement important car c'est le seul des trois sites citĂ©s a ĂȘtre rĂ©alisĂ©
dans une vraie forĂȘt tropicale humide, et les Ă©tudes y ont Ă©tĂ© menĂ©es avant et aprĂšs la
fragmentatio
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