Benjamin Girardot

Marseille · France, 13009 · +33762457465 · benjamin.girardo.pro@gmail.com

I am a PhD student at the Aix Marseille University, in Marseille, France. My main research themes are theoretical ecology, evolution, and oceanography. More specifically, I study the impacts of various perturbations on the structure and dynamics of (marine) food webs (i.e., networks of trophic interactions between species). I focus on the potential role of (past) evolution on the fragility of these food webs. I am part of the MEBIO (Marine Ecololy and BIOdiversity), team at the Mediterranean Institute of Oceanography (MIO), in Marseille.

(Scientific) Experience

PhD Student

Aix Marseille University, France

Analysis of the effects of disturbances on the structure and dynamics of marine food webs: a modeling approach.

Oct 2017 - Oct 2020

Publications

Does evolution design robust food webs ?

Proceedings of the Royal Society B: Biological Sciences
Theoretical works that use a dynamical approach to study the ability of ecological communities to resist perturbations are largely based on randomly generated ecosystem structures. By contrast, we ask here whether the evolutionary history of food webs matters for their robustness. Using a community evolution model, we first generate trophic networks by varying the level of energy supply (richness) of the environment in which species adapt and diversify. After placing our simulation outputs in perspective with present-day food webs empirical data, we highlight the complex, structuring role of this environmental condition during the evolutionary setting up of trophic networks. We then assess the robustness of food webs by studying their short-term ecological responses to swift changes in their customary environmental richness. We reveal that the past conditions have a crucial effect on the robustness of current food webs. Moreover, directly focusing on connectance of evolved food webs, it turns out that the most connected ones appear to be the least robust to sharp depletion in the environmental energy supply. Finally, we appraise the ‘adaptation’ of food webs themselves: generally poor, except in relation to a diversity of flux property.
2020

Analysis of a predator–prey model with specific time scales: a geometrical approach proving the occurrence of canard solutions

Journal of Mathematical Biology
We study a predator–prey model with different characteristic time scales for the prey and predator populations, assuming that the predator dynamics is much slower than the prey one. Geometrical Singular Perturbation theory provides the mathematical framework for analyzing the dynamical properties of the model. This model exhibits a Hopf bifurcation and we prove that when this bifurcation occurs, a canard phenomenon arises. We provide an analytic expression to get an approximation of the bifurcation parameter value for which a maximal canard solution occurs. The model is the well-known Rosenzweig–MacArthur predator–prey differential system. An invariant manifold with a stable and an unstable branches occurs and a geometrical approach is used to explicitly determine a solution at the intersection of these branches. The method used to perform this analysis is based on Blow-up techniques. The analysis of the vector field on the blown-up object at an equilibrium point where a Hopf bifurcation occurs with zero perturbation parameter representing the time scales ratio, allows to prove the result. Numerical simulations illustrate the result and allow to see the canard explosion phenomenon.
2019

Education

Aix Marseille University

Master of Oceanography - Marine Biology and ecology Specialty

Theoretical Ecology, Ecological Modeling, Statistics, Computational skills, Ecology and Evolution

Details , and see below (Skills).

September 2014 - June 2017

Aix Marseille University

Bachelor of Science, marine biology and ecology specialty
Fundamental Ecology, Oceanography, (Applied) Mathematics

Details

September 2011 - June 2014

Skills

Programming Languages & Tools
Mathematical Modelling
  • Adaptive dynamics theory toolbox (both analytical and numerical)
  • Dynamical Systems Analysis (ODE, PDE, SDE)
  • Bifurcation Theory
  • Analytical and Numerical Resolution
  • Application in Ecology
Statistics
  • Multivariate Analysis
  • Spatial Stats (Kriging)
  • Classification

Interests

It is not much refreshing to say that, as a scientist, I am fascinated by all the diverse aspects of nature. I enjoy spending my time trying to understand some of these aspects, putting together some pieces of a giant, unsolvable, puzzle that everyone is able to tackle by different perspectives. To be a little more specific, my broad scientific interests are located around the topic of complexity, with a focus on (theoretical) Ecology. I am amazed by how simple rules can lead to the emergence of so-called complex patterns.

Apart science, I dedicate my time to outdoors. I would say that I practice vertical movements sports, as I first spent a few years to do freediving, before to get (again) into climbing. What I appreciate about these sports are that in both cases, we are looking for optimized, estethic movements, mental challenges, and, more broadly, self development via sharing with sport partners.