GENERAL CONTEXT: My general topics inverstigate whether and how the structure, composition and dynamics of natural communities are affected by global changes. I mainly focus on long-term and large spatial-scale patterns and processes.

In current global changes, we should not only measure the decrease in species numbers and population sizes but also anticipate: which species (but also functions, processes and evolutionary potential) will be in trouble (or not), why, when and where?

These complex questions plead for integrative aproaches and for explicit connections between several ecological fields as well as for strong links between conservation biology and theoretical ecology.

My recent research seeks to integrate functional ecology, evolutionary ecology and biogeography to describe and explain how several facets of biodiversity (e.g., functional diversity versus phylogenetic diversity) are distributed in space and time. I use spatial analysis to shed light on the driving forces of different biodiversity facets (environmental filtering, species interactions, evolutionary history). Such integrative approach should ultimately help to reveal whether and how each facet of biodiversity can be maintained on the long run.

My research and related publications partly result from collaborative team works including: Frédéric Jiguet, Nicolas Mouquet, Romain Julliard, Wilfried Thuiller, David Mouillot, Denis Couvet, Alexandre Robert, Laurent Godet. Investigating Biogeography and large-scale conservation issues is also possible thanks to thousands of volunteers involved in citizen-science monitoring programs and people collecting and providing data.

Tracking global change impacts on biodiversity

Habitat degradation and climate changes are both known to be altering the distributions and abundances of animals and plants throughout the world. Important symptoms of these global changes are perceptible if studied at large spatial and/or temporal scales and on several species simultaneously. Moreover, biodiversity loss (or increase) is not occuring at random: Human-induced environmental changes act as a non-random filter, selecting species best able to survive within modified ecosystems. Beyond numerous decreasing losers, there are also many increasing winners.

This process coined biotic homogenization, can lead to the increase in similarity of species assemblage over space and/or time. For instance, although diversity in terms of species richness can be stable or even increase in local patches, this can be at the expense of regional diversity (if local patches are systematically colonized by similar species). But biotic homogenization is not limited to the increase in similatrity of species identity between places: this process generally masks a loss in functional or phylogenetic diversity (if colonizing species are more functionally or phylogenetically similar). To quantify this homogenization process and its driving forces, my principal approach is to measure whether species having specific traits are more at risk than others.

I have more recently focused on impact of climate warming on the composition of bird communities. In particular, we developed a simple framework to measure change in community composition in response to climate warming. This framework is based on a Community Temperature Index (CTI) which directly reflects, for a given species assemblage, the balance between low- and high-temperature dwelling species. We showed that this method is applicable to any taxa with large-scale survey data, using either abundance or occurrence data. This approach can be further used to test whether different delays are found across groups or in different land-use contexts

Connections between conservation biology and theoretical ecology

Biodiversity indicators derived from correlative studies can be highly strengthened when they are based on theoretical predictions expected from ecological theory. I am trying to derive aggregated metrics which are easy to collect and relevant for conservation purposes, but which are also easy to interpret in terms of ecological processes.

For instance, using the specialist/genralist concept is particularily useful. Indeed, natural selection induces more or less specialized strategies among species by presenting an evolutionary tradeoff between specializing to perform a few activities well, and generalizing to perform many activities fairly. According to ecological niche theory, specialists are expected to benefit from environments that are relatively homogeneous (in space and/or time) whereas generalists should benefit from environments that are heterogeneous (in space and/or time). A Community Specialization Index (CSI) reflecting the relative abundance of more or less specialized species occuring in a given community is therefore a robust biodiversity indicator not only reflecting trends in population sizes, but also a meaningful ecological process.

Working on several facet of biodiversity simulataneaously has also widespread implications on protected area planning. In particular, whether protected areas are useful to preserve functional diversity and evolutionary potential has to be assessed. To do so, biogeographical concept and tools as well as community ecology, phylogeny and evolution theory are all necessary.

Beyond scarcity: common species matter in conservation biology

The peril of endangered species is only one among many symptoms of ecosystem degradation. It is well recognized that a species-by-species approach skewed towards those mostly endangered will not be sufficient to halt the current biodiversity crisis. Global changes have motivated more and more conservationists to enlarge the scope of conservation topics from endangered species to common and familiar species, and from protected areas to the wider countryside. Yet, the need to focus on species which are not endangered is still not obvious in conservation science.

In my research, I try to show that results derived from widespread and abundant species (so-called Ordinary Nature) can be particularly useful to develop new conservation strategies. In this respect, using data from citizen-science - scientific programs involving volunteers from the general public to collect data or to perform experiments across large spatial and/or teporal scales - seems particularily relevant.

Developing citizen science and including more common and familiar species in conservation should also provide a good opportunity to go beyond the data and the measurement of biodiversity loss to encourage more value-led approaches.

Study system

I have mainly analysed datasets provided by the French Breeding Bird Survey, a citizen-science monitoring program.
I use programming, GIS, spatial statistics and phylogeny to measure empirical distribution and temporal trends of bird communities and of their caracteristics (functional and phylogenetic diversity, specialization level...)

I am also interested in meta-community models designed to allow comparison between model projections and results obtained
from biodiversity surveys (such as a regional or national survey of a particular group).