Postdoctoral Research Associate
Mechanistic modelling of biodiversity responses faces anthropic constraints
Muséum National d’Histoire Naturelle
Département Ecologie et Gestion de la Biodiversité
UMR 7204 MNHN-CNRS ’Conservation des espèces, restauration et suivi des populations’
Case postale 51
55 rue Buffon, 75005 Paris
Tel : (33) 1 40 79 36 45
Fax : (33) 1 40 79 38 35
General approaches to my research.
Keywords: Global Changes, constraints, communities, indicators, numerical model, resource, interaction, dispersion, connectivity and population, bird.
The main objective of my research is to better understand the ecological processes underlying the dynamics of communities and that at different scales. Projection models to understand the effects of global change on biodiversity suffer from the lack of a robust theoretical framework. This framework should be able to provide answers about the modalities of action of stresses associated with global change on biological communities at different scales of time and space, as well as tools (indicators) relevant to use to diagnose the state the systems studied. To try to answer all these questions I developed several original approaches, based on the design of digital model that allow me to propose mechanistic simulation tools.
The meta-communities scale
The most recent IPCC climate scenario project an increase in annual temperature by an average of 2.2°C and a decrease in precipitation of more 80 mm/year for metropolitan France by 2050 for business as usual greenhouse gas emissions scenario. Model-based studies of the impacts on biodiversity suggest that these changes in climate will substantially alter plant et animals species distributions. In addition, in Europe, these climatic changes are accompanied (past decade) by changes in the land occupations, including intensification and land abandonment in agriclutural systems, have significantly modified biodiversity. This pressure is particulary strong on farmland bird populations which have undergone severe and widespread declines. In this context, in the project MOBILIS, I construct a spatial and temporal model to mimic the dynamics of the French farmland bird communities.
Landscape connectivity, defined as the degree to which the landscape facilitates or impedes movement among resource patches, appeared as an important issue for biodiversity conservation. However, the use of landscape connectivity measures has been strongly criticized due to uncertainties in the estimation of those metrics and the lack of validation. Moreover, measures are always restricted to population level whereas management is generally carried out at the community level.
We used satellite imagery (Normalized Difference Vegetation Index NDVI) and network metrics to predict the landscape connectivity at community level for semi natural herbaceous patches in an urban area near Paris (France). We assessed the fit of these connectivity predictions to empirical data on plant communities embedded in an urban matrix.
Our results indicate that connectivity estimated with the flow metric and taking into account the matrix heterogeneity produce the best fit to the empirical data. Overall our study helped to estimate the landscape connectivity of urban area and we proposed recommendations to optimize landscape planning with respect to conservation of urban biodiversity (Muratet et al. 2012).
in collaboration with Anne Dozières
The red-bellied squirrel (Callosciurus erythraeus) was introduced on the Cap d’Antibes (Alpes Maritimes) in the late 1960s. Native to southeast Asia, this invasive Sciuridé must soon undergo a control plan initiated by the Department of Ecology (MEEDDM). For this purpose, from February to July 2010, its range has been specified, its densities were estimated in different habitat types from counts on sample itineraries, its biology and its impact have been studied, and a trapping , associated with tracking of recolonization, were performed on a test site. Since the 1990s, its range has increased by more than 12 km2. However, the A8, the last barrier limiting its expansion to the north, seems not yet crossed.
We developed a model coupling a cellular automaton which estimates the probability of dispersal and a model of metapopulation dynamics to estimate risks of extending the range of red-bellied squirrel. It can also offer different management protocols control of this expansion, by simulation scenarios.
In collaboration with Alexandre Robert and Benjamin Boisteau
The Grey Heron Ardea cinerea is now a common species in France
, however this has not always been the case. Indeed it was almost eradicated from France in the late nineteenth century by hunting and destruction. The species has been protected in France since 1975. After It’s protection after it was in 1975 that its staff has experienced impressive dynamic, enabling it to realize a recolonization of its former range repair.
A model to simulate the spatiotemporal dynamics extremely fast based in particular on the role of habitat quality can show that recolonization was accompanied by a change in the level of demand of the people, and there is a strong effect of density dependence in the spatio-temporal process (Lorrillière et al., 2010 ).
This theoretical approach has been work on the definition of constraints effects on communities and on the definition of relevant indicators to characterize these effects on community dynamics. For that several theoretical models have been developed.
Human activities are expected to lead to a variety of stochastic or directional constraints which affect species, either directly or indirectly through their resources. However, there is no theoretical framework for predicting the effects of these complex and diverse constraints on ecological communities. The development of dynamic model which mimics the use of different types of resources by a community of competing species, allows us to study the effects of different environmental constraints (directly affecting the growth rate of cash or have indirect effects on resources) on biodiversity indicators (Lorrillière et al., 2012).
A second theoretical model simulates the behavior of a food web in which individual consumers can adjust their strategy depending on food availability of biotic resources, which we submit to a sensitivity analysis. This analysis allows to identify the most sensitive parameter of a food web, species diversity of primary producers.
A final theoretical model of specialist/genralist interactions provide a general reflection on the definition of resilience at the community level. Resilience is an indicator for estimating the capacity of recovery by an ecoligical system. It can be estimated by measuring the resistance of a system to various disturbances (or its ability to maintain its equilibrium state despite the initial disturbance) or by measuring the time required for a return to baseline after a temporary disturbance. This resilience is an indicator of mechanistic effects of disturbance on ecological systems suffers from its dependence on the measured parameter to define the system state (species richness, biomass or functional indicators). That is why I am currently working to develop an integrative indicator of this resilience which introduced the original concept of meta-resilience.
Other research topics : the MAS (Mutli-Agents Systems)
In collaboration with Pauline Teillac-Deschamp, Véronique Servais, Antoine Cadi et Anne-Caroline Prévot-Julliard
Trade in turtle (exported from United States ) began in the 1970s. Among these “Florida turtles,” the species was the most represented is the red-eared slider Trachemys scripta elegans.
Raised in good conditions, this new exotic pet (NAC), grew up and can become troublesome for some families of owners (adult turtle can measure up to 28 cm and weigh up to 3 kg and long life such as several decades). A number of owners then decided to “get rid” of their turtle and releasing them into the wild. People often have released their turtle thinking them free, feeling concerned about his welfare. So this is a case is particular in the context of invasive species because this species was actively introduced by the owners and the public have an emotional connection with these turtles.
It is in this context that the program “Red-eared Slider” was initiated in the laboratory “Ecologie, Systématique et Evolution” (http://tortues.floride.u-psud.fr/).
A Multi-Agent Systems, or MAS, has been designed like an aid to reflection to bring a new point of view to the manager of this socio-ecological problems.
It shows that direct actions have only few short-term effects on the abundance of wild turtles in green spaces and have no effect on the level of public concern about environmental issues. It also show that a mixture of different communication strategies improved the awareness and attitudes towards issues related to introduced species (Teillac-Deschamps et al., 2010).