Small-mammal assemblage response to deforestation and afforestation in central China

International audienceDeforestation is a major environmental issue driving the loss of animal and plant species. Afforestation has recently been promoted to conserve and restore Chinese forest ecosystems. We investigated the distribution of small-mammal assemblages in an area where forest and associated deforestation habitats dominate and in an agricultural area where afforestation is ongoing in the Loess Plateau of southern Ningxia Autonomous Region, P.R. China. Multiple trapping was used. Assemblages were defined based on the multinomial probability distribution and information theory. Species turnover between assemblages of deforested and afforested habitats was high, although no clear effect on species richness was observed. The two assemblages described along the deforestation gradient displayed higher diversity, whereas diversity was lower in assemblages identified in afforested habitats where Cricetulus longicaudatus, known agricultural pest in various areas of China, clearly dominated. The threatened Sorex cylindricauda and Eozapus setchuanus were recorded along the deforestation gradient but not in plantations. Therefore, habitats present along a deforestation succession in this part of Ningxia sustain a high diversity of small mammals and include species of conservation concern. At the present stage of its process (maximum 15 years), afforestation in southern Ningxia favours the dominance of an agricultural pest

Range shifts or extinction? Ancient DNA and distribution modelling reveal past and future responses to climate warming in cold-adapted birds.

Global warming is predicted to cause substantial habitat rearrangements, with the most severe effects expected to occur in high-latitude biomes. However, one major uncertainty is whether species will be able to shift their ranges to keep pace with climate-driven environmental changes. Many recent studies on mammals have shown that past range contractions have been associated with local extinctions rather than survival by habitat tracking. Here, we have used an interdisciplinary approach that combines ancient DNA techniques, coalescent simulations and species distribution modelling, to investigate how two common cold-adapted bird species, willow and rock ptarmigan (Lagopus lagopus and Lagopus muta), respond to long-term climate warming. Contrary to previous findings in mammals, we demonstrate a genetic continuity in Europe over the last 20 millennia. Results from back-casted species distribution models suggest that this continuity may have been facilitated by uninterrupted habitat availability and potentially also the greater dispersal ability of birds. However, our predictions show that in the near future, some isolated regions will have little suitable habitat left, implying a future decrease in local populations at a scale unprecedented since the last glacial maximum

Éléments d'écologie de la transmission d'Echinococcus multilocularis en Chine (Sichuan) Modélisation des distributions spatiales des communautés et populations des hôtes : des données de terrain aux prédictions

The transmission of the parasite Echinococcus multilocularis causing a fatal zoonosis in humans, the alveolar echinococcosis, can be modulated by anthropogenic disturbances of its intermediate (small mammals) and definitive (canids) host ecology. We studied some ecological parameters of those host populations in the Sichuan Province, China, where high human prevalences are observed. On the basis of trapping data sets, the definition of small mammal assemblages has provided a way to resume the large diversity observed in sampled habitats and trapped species. We found that multiple non-linear regressions was the most performant method to model assemblage distributions along environmental gradients extracted from satellite images, such as slope, elevation and vegetation indices. While local models were not transferable on study sites distant from one hundred km, a regional classification of transmission groups could have been realized on the whole regional data set. Then, analysis of spatial distributions of canid faeces, their contaminations as well as nocturnal trajectories of dogs equipped with GPS collars, were done to assess and quantify the predominant contribution of dog over fox in the environmental contamination and to localise areas of high transmission risk, closed to human habitations. Finally, spatial interactions between dogs and small mammals were found inside villages and can be considered as a preliminary estimation of host contact rate required in transmission models.La transmission du parasite Echinococcus multilocularis à l'origine d'une zoonose fatale chez l'homme, l'échinococcose alvéolaire, peut être modulée par des perturbations anthropiques de l'écologie des populations de ses hôtes intermédiaires (micro-mammifères) et définitifs (canidés). Nous avons étudié des paramètres écologiques des populations de ces hôtes dans la province du Sichuan, en Chine, où sont observées de fortes prévalences humaines. Sur la base de données de piégeage, la définition d'assemblages d'espèces de micro-mammifères a permis de résumer la grande diversité des habitats échantillonnés et des espèces piégées. Nous avons trouvé que les régressions multiples non-linéaires étaient la méthode la plus performante pour modéliser les distributions des assemblages le long de gradients environnementaux extraits d'images satellites telles que l'altitude, la pente et des indices de végétation. Alors que les modèles locaux n'étaient pas transférables sur des sites distants d'une centaine de km, une classification régionale des groupes de transmission a pu être établie. D'autre part, les analyses des distributions spatiales des fèces de canidés, de leurs contaminations et des trajectoires nocturnes de chiens équipés de colliers GPS ont permis de confirmer et de quantifier le rôle prédominant du chien sur le renard dans la contamination environnementale et de localiser des zones à haut risque de transmission près des habitations. Enfin, des interactions spatiales entre les chiens et les micro-mammifères ont été mises en évidence dans les villages et constituent une estimation préliminaire du taux de contact entre les hôtes requis pour modéliser la transmission

Towards understanding the impacts of environmental variation on Echinococcus multilocularis transmission

International audienceA key element in disease emergence/re-emergence is ecosystem disruption as a result of anthropogenic effects which may be as rapid as in forestry and agricultural changes. There is however difficulty in developing suitable models to study ecology of infectious diseases, wherein spatial determinants that meaningfully characterize wildlife reservoir habitat, can be linked in turn to host ecology and to dynamics of pathogen/parasite transmission. Spatial variables in the form of landscape and socio-economic characteristics should be linked to parasite transmission dynamics using an integrated modeling approach that takes into account multi-level heterogeneity at habitat, host and parasite domains and deterministic transmission parameters. The diversity of small mammals host communities and landscape worldwide offer a number of systems that sustain transmission of E. multilocularis at various time-space scales. It is expected that further advances will come from methods combining quantification of host communities from field surveys, landscape via remote sensing and parasite transmission via population screenings conducted on definitive hosts (e.g. dogs in villages in China or foxes in Europe) and humans, in a spatially explicit context. The combination of multi-level field approaches with modern regression techniques coupled with traditional transmission models provide a unique opportunity of investigating how a diversity of small mammal communities and anthropogenic landscapes can regulate parasite transmission

Predictive mapping of host assemblages: an example with small mammals in western China

Linking host spatial distributions to environmental variables can provide key information for understanding and predicting the transmission of a parasite in space. When a large number of potential intermediate hosts co-occur within a diversity of habitats, community level modelling helps to summarize such complex data set by defining groups of species/sites, i.e assemblages. We built a predictive model for the niches of small mammal assemblages including potential Echinococcus multilocularis intermediate hosts, in two areas of western China (Sichuan) by a three step modelling procedure. First, 8 assemblages were defined using a multinomial logistic model associated with a redundancy reduction procedure. Then, niches of these assemblages were modelled w.r.t. the environmental space of each sampled area using a Multiple Adaptative Regression Spline. Elevation and ETM band 6 (land surface temperature) were one of the main factors influencing assemblage distributions in both study areas. The importances of vegetation indices (NDVI and EVI) effects, which are corelated to the amount of vegetation, differed between the two locations. Finally, the model providing the lowest predictive classification error was chosen to map assemblage occurence probabilities beyond the sampled locations. We could thus discuss the predictive error component induced by extrapolation of model predictions on non trained locations

Habitat modelling of small mammals assemblages in Western Sichuan (China): from locally trained models at landscape scale to regional predictive mapping

International audienceBuilding predictive maps of assemblage habitat, a widely used method in conservation and landscape management, is based on fitting habitat model on a training area, corresponding to a limited region in the environmental space. Model predictive performances need to be robustly evaluated on test data set. This is often realized at the landscape level, i.e taking as test data set one part of the original sample or a resampling one. Predicting assemblage occurrences at a regional level requires a step further in the modelling validation stage: testing model extrapolation performances. We estimated and compared the predictive performances of two scales of predictive mapping of small mammals assemblages in a remote area of Sichuan province. Small mammal assemblages were defined in two distant areas and differed between both areas. Their habitats were modelled, predicted and mapped using ETM bands at two different spatial scales: local (in each area) versus regional (including both areas). While locally trained models provided large predictive errors on independent data sets, the regionally trained model more accurately predicted assemblage occurrences and could be considered at this state of the research as an appropriate method to map assemblage regionally

Rodent assemblages in the Llanos de Ojuelos, northeastern Jalisco, Mexico: a landscape approach

International audienceThe Llanos de Ojuelos is an extensive llanura at the southern end of the Chihuahuan Desert. The original composition of the land is mostly grasslands, with interspread shrublands, and small water bodies. Currently, 80% of the area is used for crop production and/or grazing of livestock. As a result, natural habitats have been severely fragmented, and the overall biodiversity affected to an unknown degree. The present work aims at understanding the relationship between rodent assemblages and different types of habitat patches to integrate a landscape approach of small mammal diversity. In the spring of 2008 we inventoried the rodents at 74 locations in the area, through the use of Sherman live-traps (40 traps during two nights, per site; total=5920 night-traps). We covered the major perennial vegetation types. We captured 458 individuals of 20 species of rodents (Perognathus flavus, Chaetodipus hispidus, Chaetodipus nelsoni, C. pennicillatus, Dipodomys ordii, D. merriami, D. phillipsii, Liomys irroratus, Peromyscus boylii, P. difficilis, P. eremicus, P. gratus, P. maniculatus, P. melanophrys, Reithrodontomys fulvescens, R. megalotis, Baiomys taylori, Neotoma goldmani, N. leucodoni, and Onychomys arenarius). We defined a priori 11 rodent habitat categories based on the cover, structure and dominant plant species. Species presence/absences were modeled jointly through a multinomial model, and then used to pool habitats by merging all habitat classes pair-wise and selecting the most parsimonious model by the Akaike Information Criterion for each iteration. This produced 7 habitat classes: Closed arboreal nopalera, mixed nopalera, grassland, leguminous scrubland, Dodonaea scrubland, cultivated nopalera, and oak scrub. Rodent communities analyzed have low levels of organization, with most species thriving in a variety of conditions, although some of them exhibited a certain habitat preference. Communities were distributed according to a gradient from "low open vegetation" to "dense tall vegetation," with fuzzy borders between them. The highest rodent richness was in nopaleras; mid richness, in leguminous scrub communities, and lower richness, in grasslands. This might have resulted from differences in habitat structure and within-habitat heterogeneity. Habitat types seemed also to be structured differently. We are exploring models employing reflectance data to classify satellite images according to habitat classes and to analyze their spatial relationship. Given the patchiness and the low organization level of the communities, biological conservation cannot be carried out in homogeneous areas, but must consider the entire landscap

Reflectance as a predictor for rodent species in the semiarid landscape Llanos de Ojuelos México

International audienceAlthough Mexico's central arid and semiarid lands face numerous conservation problems, they have largely been neglected from conservation, despite their apparent biological importance. We studied the semiarid Llanos de Ojuelos, where the original plant communities of grasslands, shrublands, and patches of oaks have been modified strongly by cattle grazing and for cultivation, affecting animal populations and communities, as well as the landscape-level ecological dynamics. Very little about the populations of wild animals in the area and the processes underlying their distribution and dynamics is known. We focused on whether satellite information was useful to explain rodent distributions and abundances in this area with a complex landscape of diffuse plant communities. In the spring of 2008 we inventoried the rodents at 74 locations in the area, through the use of Sherman live-traps (40 traps during two nights, per site; total=5920 night-traps). We covered the major perennial vegetation types. The existence of a complex landscape of intergrading grasslands, Opuntia comunities and shrublands (dominated by Acacia, Mimosa, Dodonaea, and Quercus) of different types and composition creates rich habitat mosaic that promotes a rich rodent fauna. We captured 20 species of rodents (458 individuals), while richness was estimated at 21-25 species. Reithrodontomys fulvescens, Chaetodipus nelsoni, Dipodomys phillipsii, Peromyscus melanophrys, Peromyscus gratus, and Peromyscus difficilis were very common at our sites, while Chaetodipus pennicillatus, Liomys irroratus, Perognathus flavus, Dipodomys merriami, Reithrodontomys megalotis, Peromyscus boylii, Neotoma leucodon, Peromyscus eremicus, Dipodomys ordii, and Peromyscus manicultatus were common, and Neotoma goldmani, Chaetodipus hispidus, Onychomys arenarius, and Baiomys taylori were rare. To explore the value of satellite information to understand and predict the rodents' distributions, we derived reflectance data from all bands of a Landsat5 TM Image (5 March 2008) for each trapline's midpoint. We will compare each rodent species' abundance with this data as well as with the normalized difference vegetation index (NDVI) and tasseled cap transformations (TCs: brightness, greenness, and wetness). We will link rodent presence/absences to reflectance values through linear and non-linear discriminant analysis, as well as through general linear models and multiple adaptive regression splines. Satellite images classified following the best models will then be interpreted according to field expertise. As end results we expect to have a better understanding on the rodent species' ecology, an adequate image classification procedure, and potential distribution maps for the rodent species in the study area