Oportunidad de proyecto de master en Francia

Spatio-temporal dynamics of populations subject to environmental perturbations on heterogeneous habitats.
Contact: estelle.pitard@umontpellier.fr


Who: Master students interested in a multidisciplinary approach combining ecology and statistical physics, and the link between theoretical models and real data. The internship is typically for 6 months, with a salary.
With whom : Estelle Pitard (L2C, Département de Physique, Montpellier, France, estelle.pitard@umontpellier.fr). The student will be mainly located in Laboratoire Charles Coulomb (L2C, Montpellier) and will interact with the supervisor, as well as other researchers in ecology and remote-sensing science in Montpellier.
What problem : Of fundamental and applied interest in ecology is the study of how populations from the same species are distributed in space as a result of colonization and extinction processes. Such processes depend on the spatial configuration of the habitat as well as the colonization and establishment possibilities in space and time.
While the colonization-extinction dynamics of populations can usually be tackled using metapopulation theory (Hanski and Gilpin 1997, Levins 1969), the spatio-temporal generic or non-generic properties emerging from such models on structured habitats are only partially known. However, quantitative information is needed for practical purposes related to conservation and management issues. More and more data become available concerning the distribution of species over space and time which, combined with suitable models could be used in order to predict future dynamics.
A previous PhD work consisted in the study of the stochastic dynamics of colonization and extinction of one species on a habitat consisting of islands of various sizes. (Huth et al. 2015 and Figure 1). Unexpected dynamical regimes were found, such as a significant slowing down of the extinction dynamics due to the heterogeneous character of the island size distribution. This effect is of practical relevance as it shows that an apparent short-time persistent state of populations might be the precursor of a very slow extinction dynamics at large times.
Following the lines of this general study, our goal is to study the dynamical properties of the population models and the consequences of the extinction regime in different environmental conditions :
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As an extension of the island model proposed by Huth et al. (2015), study the population dynamics on a percolating and/or aggregated spatially explicit 2D habitat (Huth et al. 2014), and study the effect of the temporal variability of the habitat quality by varying colonization and extinction rates. We will study dynamical models where the habitat is heterogeneous and where the temporal evolution of the populations is perturbed by a change in colonization and extinction parameters. These changes can be either periodic -for seasonal variations- or local in time and/or space – for accidental external perturbations . In each case, the resilience capacity of the populations will be assessed.
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The models will be extended to realistic habitat maps of vegetation in wetlands. The project’s bigger scope is to put together theoretical models of populations dynamics on fragmented habitats and real data collected from field campaigns and remote-sensing (satellites) techniques, one example being the high-frequency, high spatial resolution data
of pondweed occurrence collected in the Grand Bagnas pond, near Agde in the south of France (Menu et al 2018 and Figure 2). The intern will help develop adapted machine- learning methods to classify data and learn from data in the objective of predicting future dynamics.
Figure 1- Metapopulation model (Huth et al, 2015).
Figure 2- Spatio-temporal evolution of the Grand Bagnas pondweed beds, maps obtained after data classification of Sentinel 2 satellites images. (Menu et al, 2018).
(available upon request)
References :
-Hanski, I. A. and Gilpin, M. E. 1997. Metapopulation Biology. – In, Academic Press, pp. 525.
-Hanski, I. 1998. Metapopulation dynamics. – Nature 396: 41-49.
-Hiebeler, D. 2000. Populations on fragmented landscapes with spatially structured heterogeneities: landscape
generation and local dispersal. – Ecology 81: 1629-1641.
-Houchmandzadeh, B. 2009. Theory of neutral clustering for growing populations. – Physical Review E 80,
051920.
-Houchmandzadeh, B. 2008. Neutral clustering in a simple ecological community. – Physical Review Letters 101,
078103.
-Huth G., A. Lesne, F. Munoz, and E. Pitard. 2014. Correlated percolation models of structured habitat in ecology.
– Physica A: Statistical Mechanics and its Applications 416:290-308.
-Huth G., B. Haegeman, E. Pitard, and F. Munoz. 2015. Long-Distance Rescue and Slow Extinction Dynamics
Govern Multiscale Metapopulations. – The American Naturalist 186:460-469.
-Menu M., Papuga G., Andrieu F., Debarros G., Alleaume S., Pitard E. 2018. Using remote-sensing data to model
the spatio-temporal dynamics of pondweed in the Grand Bagnas lagoon, preprint.
-Munoz F., Huth G, Pitard E., 2018. Boundary constraints on population dynamics in a percolating habitat. – Ecological Complexity 36:230-238.