Sébastien OLLIER

My previous research has focused on understanding how global trade networks shape the dispersal, establishment, and long‑term dynamics of invasive insects. Working within a socio‑ecological perspective, I have shown how the structure, geography, and history of commodity flows drive the trajectories of alien species worldwide. My work has revealed that trade composition and temporal changes in supply chains strongly influence invasion rates (“Precise knowledge of commodity trade is needed to understand invasion flows”), and that recurrent bridgehead effects distort global dispersal pathways and accelerate the worldwide spread of invasive ants. By integrating economic data, biogeography, and invasion ecology, I helped clarify the mechanisms by which human activities govern species movements (“Alien insect dispersal mediated by the global movement of commodities”, “Global flows of insect transport and establishment”). These contributions provided quantitative frameworks to understand how societal choices and economic systems translate into ecological outcomes at global scales.

My actual research focuses on understanding how environmental variation shapes functional traits, ecological niches, and species’ responses to global change. Combining microclimate‑centred fieldwork, automated extraction of morphological and colour traits, and macroecological and phylogenetic modelling, I develop a scale‑explicit framework linking fine‑scale environmental conditions to large‑scale biodiversity patterns. Social insects—particularly ants—serve as my primary study system due to their ecological dominance, global distribution, and diverse nesting and thermoregulatory strategies. My work is structured around two main axes:

(1) colouration and morphology across environmental gradients, integrating microclimate measurements, image‑based trait pipelines, and comparative methods;

(2) environmental drivers of social organization, focusing on how social syndromes mediate species’ capacity to exploit heterogeneous or extreme environments.

By bridging micro‑ and macroecology, my research aims to improve predictions of species resilience, community assembly, and invasion risk under ongoing climate change.

I have over fifteen years of teaching experience across Bachelor, Master and doctoral levels, with a strong focus on quantitative ecology, statistics, spatial analysis, and biodiversity measurement.

At the University Paris‑Saclay, I delivered approximately 192 hours of teaching per year in courses ranging from inferential statistics and multivariate analysis to geocomputation in R, GIS, ecosystem ecology, and bioinformatics.

Since joining the University of Lausanne, I have continued to teach quantitative methods at Bachelor and Master levels and to contribute to doctoral training through CUSO, where I developed two specialised courses on spatial data handling and biodiversity metrics.

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