Theme DyBRES - Dynamics of spatial ecological networks

Context and challenges

Modelling ecosystem dynamics in a heterogeneous and changing environment is a major challenge to address the sustainability of their services and ensure the persistence of endangered species. We investigate species dynamics in fragmented habitats, according to local population dynamics and colonization processes across fragments. The local ecosystems constitute the nodes of a complex ecological network whose edges represent the migration flows.
The major issues are: (1) how to define the nodes and edges of the network in a relevant way, (2) how to characterize the topology of the resulting complex network, (3) how to model species and ecosystem dynamics on the network, and (4) how to assess the impact of these dynamics on species persistence and ecosystem services over the short, medium and long term.

Objectives

We wish to characterize local and regional patterns of biodiversity resulting from species dynamics on their habitat network (direct problem). We will subsequently infer species abilities to colonize habitat fragments and to survive locally from observed occupancy patterns (inverse problem). We will then predict expected biodiversity dynamics on networks undergoing habitat loss and degradation, or altered connectivity. The approach can be applied in a retrospective approach to assess the footprint of past dynamics on current biodiversity patterns, as well as to forecast biodiversity dynamics under future scenarios of environmental changes. This work is expected to provide diagnostic and monitoring indicators tools for the conservation and management of ecological networks.

Approach

The spread of species on spatial networks is addressed through metapopulation and metacommunity models. A contact process of metapopulation dynamics involves a phase transition between regional persistence and regional extinction. Much remains to be done to characterize more precisely the expected spatial patterns of habitat occupancy, and to detect transient dynamics.
Particular attention is paid to the phenomenon of catastrophic change associated with the phase transition to species and ecosystem collapse. Some studies claim that spatial patterns precursor to such transition can be detected and provide early-warning signals, but they are not unambiguous. Moreover, the extinction debt phenomenon (very slow transition toward extinction) is poorly understood and still very important for biological conservation. Our work can contribute to better understand and better evaluate these phenomena.
We will build on modelling frameworks and case studies relevant to test our hypotheses on species dynamics on habitat networks:

  •  Mediterranean temporary ponds: study of the spatial diversity of amphibians and plants forming specialized guilds. Inference of their properties of colonization and survival, depending on their spatial distribution and on the quality of the landscape matrix between the ponds.
  •  Networks of agricultural and natural habitats in South France and Corsica: characterization of the network structure for each habitat types (agricultural areas, meadows, woodlands), and of the connectivity of network nodes. Design of indicators and diagnosis tools of ecological network quality.

The project is based on an interdisciplinary research group (DyBRES), with complementary skills in ecology, mathematics and physics that are required to address the major theoretical and methodological issues.

Expected results

Our work is basically focused on theoretical and conceptual modelling, but also aims to provide applied outcomes (indicators and tools to help network design of protected areas and ecological networks).

Scientific projects

Acronym Title Duration
DISCO-WEEDAssemblage des communautés adventices : entre processus écologiques et perturbations 2016 - 2019
EXPLABIOExplanations in Evolutionary Biology2014 - 2016
CARHABCartographie nationale des habitats2013 - 2016

Major publications

All publications
  • Huth, G., et al., 2014. Correlated percolation models of structured habitat in ecology. Physica A: Statistical Mechanics and its Applications, 416: 290-308. [Editor link]
  • Munoz, F., et al., 2014. How do habitat filtering and niche conservatism affect community composition at different taxonomic resolutions?. Ecology, 95(8): 2179–2191. [Editor link]
  • Munoz, F., et al., 2008. Beta-diversity in spatially implicit neutral models: a new way to assess species migration. The American Naturalist, 172(1): 116-127. [Editor link]
  • Munoz, F., et al., 2007. Spectral analysis of simulated species distribution maps provides insights into metapopulation dynamics.Ecological Modelling, 205: 314-322. [Editor link]
  • Munoz, F., et al., 2007. Estimating parameters of neutral communities: from one Single Large to Several Small samples. Ecology, 88(10): 2482-2488. [Editor link]