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Gallien L.,University Grenoble alpes | Gallien L.,French National Center for Scientific Research | Thuiller W.,University Grenoble alpes | Thuiller W.,French National Center for Scientific Research | And 11 more authors.
PLoS ONE | Year: 2016

Climatic niche shifts have been documented in a number of invasive species by comparing the native and adventive climatic ranges in which they occur. However, these shifts likely represent changes in the realized climatic niches of invasive species, and may not necessarily be driven by genetic changes in climatic affinities. Until now the role of rapid niche evolution in the spread of invasive species remains a challenging issue with conflicting results. Here, we document a likely genetically-based climatic niche expansion of an annual plant invader, the common ragweed (Ambrosia artemisiifolia L.), a highly allergenic invasive species causing substantial public health issues. To do so, we looked for recent evolutionary change at the upward migration front of its adventive range in the French Alps. Based on species climatic niche models estimated at both global and regional scales we stratified our sampling design to adequately capture the species niche, and localized populations suspected of niche expansion. Using a combination of species niche modeling, landscape genetics models and common garden measurements, we then related the species genetic structure and its phenotypic architecture across the climatic niche. Our results strongly suggest that the common ragweed is rapidly adapting to local climatic conditions at its invasion front and that it currently expands its niche toward colder and formerly unsuitable climates in the French Alps (i.e. in sites where niche models would not predict its occurrence). Such results, showing that species climatic niches can evolve on very short time scales, have important implications for predictive models of biological invasions that do not account for evolutionary processes. © 2016 Gallien et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source


Violle C.,CNRS Center of Evolutionary and Functional Ecology | Choler P.,University Grenoble alpes | Choler P.,French National Center for Scientific Research | Borgy B.,CNRS Center of Evolutionary and Functional Ecology | And 21 more authors.
Science of the Total Environment | Year: 2015

The effect of biodiversity on ecosystem functioning has been widely acknowledged, and the importance of the functional roles of species, as well as their diversity, in the control of ecosystem processes has been emphasised recently. However, bridging biodiversity and ecosystem science to address issues at a biogeographic scale is still in its infancy. Bridging this gap is the primary goal of the emerging field of functional biogeography. While the rise of Big Data has catalysed functional biogeography studies in recent years, comprehensive evidence remains scarce. Here, we present the rationale and the first results of a country-wide initiative focused on the C3 permanent grasslands. We aimed to collate, integrate and process large databases of vegetation relevés, plant traits and environmental layers to provide a country-wide assessment of ecosystem properties and services which can be used to improve regional models of climate and land use changes. We outline the theoretical background, data availability, and ecoinformatics challenges associated with the approach and its feasibility. We provide a case study of upscaling of leaf dry matter content averaged at ecosystem level and country-wide predictions of forage digestibility. Our framework sets milestones for further hypothesis testing in functional biogeography and earth system modelling. © 2015 Elsevier B.V. Source


Pellissier L.,University of Lausanne | Brathen K.A.,University of Tromso | Vittoz P.,University of Lausanne | Yoccoz N.G.,University of Tromso | And 9 more authors.
Global Ecology and Biogeography | Year: 2013

Aim: Understanding the stability of realized niches is crucial for predicting the responses of species to climate change. One approach is to evaluate the niche differences of populations of the same species that occupy regions that are geographically disconnected. Here, we assess niche conservatism along thermal gradients for 26 plant species with a disjunct distribution between the Alps and the Arctic. Location: European Alps and Norwegian Finnmark. Methods: We collected a comprehensive dataset of 26 arctic-alpine plant occurrences in two regions. We assessed niche conservatism through a multispecies comparison and analysed species rankings at cold and warm thermal limits along two distinct gradients corresponding to (1) air temperatures at 2m above ground level and (2) elevation distances to the tree line (TLD) for the two regions. We assessed whether observed relationships were close to those predicted under thermal limit conservatism. Results: We found a weak similarity in species ranking at the warm thermal limits. The range of warm thermal limits for the 26 species was much larger in the Alps than in Finnmark. We found a stronger similarity in species ranking and correspondence at the cold thermal limit along the gradients of 2-m temperature and TLD. Yet along the 2-m temperature gradient the cold thermal limits of species in the Alps were lower on average than those in Finnmark. Main conclusion: We found low conservatism of the warm thermal limits but a stronger conservatism of the cold thermal limits. We suggest that biotic interactions at the warm thermal limit are likely to modulate species responses more strongly than at the cold limit. The differing biotic context between the two regions is probably responsible for the observed differences in realized niches. © 2013 John Wiley & Sons Ltd. Source


Bonnet V.,Conservatoire Botanique National Alpin | Fort N.,Conservatoire Botanique National Alpin | Dentant C.,Parc National des Ecrins | Bonet R.,Parc National des Ecrins | And 3 more authors.
Acta Botanica Gallica | Year: 2015

There is an increasing need for data on the patterns of population changes for rare species at the regional, national and European scales in the context of the Natura 2000 reporting on the state of species conservation. This reporting requires the use of the same protocol over a whole region or country with the major constraint that it has to be shared by a large array of conservations and monitoring structures. The protocol has therefore to be both precise and reproducible but also simple enough to be used over a large number of sites and years, and has moreover to be accepted by various conservation structures.In this aim, the Alps-Ain flora conservation network (Réseau Alpes-Ain de Conservation de la Flore), a network composed of flora conservation stakeholders for 2 regions, Provence-Alpes-Côte dAzur and Rhône-Alpes, set up a series of nested protocols to monitor populations at different spatial scales (levels). Each monitoring level is set up to answer to a specific aim and corresponds to a protocol shared by all the network actors. The first level, detailed below, is defined for the regional scale ("territory" level) with the site as observation unit. The second level aims at identifying if in a specific site ("station") a population is stable, expanding or regressing and if natural or anthropic factors can explain this dynamics. The observation unit is a plot or a transect and the variables measured are frequencies or numbers and environmental parameters. The third level is an individual-based survey ("individu") and aims at understanding the demographic processes affecting a population. The observation unit is here the individual plant. The link between the 3 levels is described in Figure 1.The "territory" level protocol was developed over several years of discussions and in situ tests on several species (Table 1). Its aim is to identify increases or decreases of species size at the scale of the region. The variables used for this monitoring are simple and easily reproducible: area of presence and frequency. During the process, we realized that even a simple protocol could not be applied to a large range of species. We therefore propose some variations on a common methodological base, depending on the biology of the species (longevity, clonality, dormancy, size of individuals.). An originality of the protocol is to note the non-detection of the species in a given point at a given time to be able to document the expansion or the regression of the species in the site. A first step therefore consists in defining the zone in which the species will be looked for, the prospection zone (ZP). This zone should correspond as much as possible to the potential habitat of the species and has to remain constant over time. Within this zone, the area of presence (AP) is determined using the envelope formed by the GPS points where the species is found. Population size is then estimated as the frequency of occurrence by contact-points along at least two transects positioned so as to take into account the environmental heterogeneity of the site (see Figure 1). For species that have very variable population sizes and distributions, the transects should be representative of the AP; for species with very stable populations, we recommend fixed transects to reduce year-to-year and spatial variations, however managers are free to choose the location of the transects. At least 100 points are taken for each transect in order to have a robust estimate of the frequency of occurrence. For species with low ground cover, we suggest replacing the contact-point by contact-areas, i.e. small plots positioned similarly to the points along the transects. The areas of the plots have to be decided in advance and should not change over time. The aim is to avoid extreme frequency values (close to 0 or 1) in order to be able to detect an increase or a decrease in population size. Each prospection zone corresponds to one data point. At the regional scale, the population is represented by the ensemble of the ZPs. To have a good estimate of the population size and its dynamics, the ZPs should correspond to a random or a stratified sample of all the existing sites. This is however difficult and in practice, the ZPs of the survey are the ones for which an organism can commit itself. The RAACF then has to make sure that the sample of ZPs is representative of the species distribution. The frequency of the survey depends on the biological characteristics of the species. For perennial species we suggest a time step of 3 to 5 years in the absence of catastrophic events. For annual or dormant species, the survey should be performed over 3-5 consecutive years in order to have a reliable estimate of AP and size and to smooth out the inter-annual (normal) fluctuations, and then repeated 3-5 years later. A web-service database was developed by the network to ensure the aggregation of the data. This method is a practical answer to the EU requirements in terms of assessment of populations of plant species in the framework of the EU Habitats Directive (Council Directive 92/43/EEC). © 2014 © 2014 Société botanique de France. Source


Meynard C.N.,Montpellier SupAgro | Lavergne S.,CNRS Alpine Ecology Laboratory | Boulangeat I.,CNRS Alpine Ecology Laboratory | Garraud L.,Conservatoire Botanique National Alpin | And 3 more authors.
Journal of Biogeography | Year: 2013

Aim: Metacommunity theories attribute different relative degrees of importance to dispersal, environmental filtering, biotic interactions and stochastic processes in community assembly, but the role of spatial scale remains uncertain. Here we used two complementary statistical tools to test: (1) whether or not the patterns of community structure and environmental influences are consistent across resolutions; and (2) whether and how the joint use of two fundamentally different statistical approaches provides a complementary interpretation of results. Location: Grassland plants in the French Alps. Methods: We used two approaches across five spatial resolutions (ranging from 1 km × 1 km to 30 km × 30 km): variance partitioning, and analysis of metacommunity structure on the site-by-species incidence matrices. Both methods allow the testing of expected patterns resulting from environmental filtering, but variance partitioning allows the role of dispersal and environmental gradients to be studied, while analysis of the site-by-species metacommunity structure informs an understanding of how environmental filtering occurs and whether or not patterns differ from chance expectation. We also used spatial regressions on species richness to identify relevant environmental factors at each scale and to link results from the two approaches. Results: Major environmental drivers of richness included growing degree-days, temperature, moisture and spatial or temporal heterogeneity. Variance partitioning pointed to an increase in the role of dispersal at coarser resolutions, while metacommunity structure analysis pointed to environmental filtering having an important role at all resolutions through a Clementsian assembly process (i.e. groups of species having similar range boundaries and co-occurring in similar environments). Main conclusions: The combination of methods used here allows a better understanding of the forces structuring ecological communities than either one of them used separately. A key aspect in this complementarity is that variance partitioning can detect effects of dispersal whereas metacommunity structure analysis cannot. Moreover, the latter can distinguish between different forms of environmental filtering (e.g. individualistic versus group species responses to environmental gradients). © 2013 Blackwell Publishing Ltd. Source

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