Research

My research broadly addresses questions related to the origins of biodiversity. To do so I both use theoretical models and empirical datasets. Plants are my favorite study system to address such questions.


1) Evolution of the Alpine flora

I am interested in the origins and evolution of alpine floras, especially that of the European Alps, where I live. Alpine floras are interesting per se because they occupy some of the harshest environments on Earth, but they are also convenient study systems because they are somehow simplified: they occupy discrete sets of environmental patches above the treeline where local communities have relatively low diversity and abiotic factors often predominate.

My research covers various temporal and spatial scales ranging from broad-scale biogeography across the globe to the finest details of phylogeography within some parts of the European Alps. Topics that I investigate range from molecular systematics to the details of the speciation process. In particular, I am interested in the complementary roles played by biogeographic barriers, adaptation to different substrates, and hybridation in the origins of the alpine plant species.

Some selected species from Primula sect. Auricula, the largest clade of plants from the European Alpine System. From left to right: P. minima, P. auricula, P. glutinosa and P. apennina

Collaborators: Sébastien Lavergne, Lara Wootton, Camille Voisin, Cédric Dentant, Marion Deville-Cavellin, Gabriele Casazza, Elena Conti, Serge Aubert, Philippe Choler, Cristina Roquet

Relevant publications: Voisin et al. 2023 Alpine Botany, Boucher et al. 2021 Scientific Reports, Theodoridis et al. 2017 Systematic Biology, Casazza et al. 2017 Annals of Botany, Boucher et al. 2016 Molecular Phylogenetics and Evolution, Boucher et al. 2016 Perspectives in Plant Ecology Evolution and Systematics, Aubert et al. 2014 Alpine Botany, Roquet et al. 2013 Journal of Biogeography


2) Geodynamic effects on biodiversity

My past research has made me realize that the physical environment in which species occur is a key factor shaping their evolution. Landscapes with their topography, abiotic conditions, vegetations, etc. often set the stage for the evolution of organisms. Several pieces of my work have investigated how various aspects of the environment, like its spatial heterogeneity, its level of fragmentation and its historical dynamics, influenced species diversification. 

To study these processes I use phylogenetic tools but most importantly I rely on collaborations with geologists. 

Paleogeography of the Sunda shelf: before the last 400,000 yrs Sundaland was permanently emerged, which enabled organisms from evergreen tropical forest to disperse easily between the Malay Peninsula and the islands of Indonesia, as symbolized by arrows. Our results show that after the first inundation of Sundaland many terrestrial organisms started diverging, leading to different lineages on isolated land masses. From Husson et al. 2020.

Collaborators: Yanis Bouchenak-Khelladi, Laurent Husson, Anta-Clarisse Sarr, Rafael Wüest, Tony Verboom

Relevant publications:  Wüest et al. 2019 Journal of Biogeography  ; Husson et al. 2020 Journal of Biogeography ; Verboom et al. 2020 Systematic Biology


3) Speciation & systematics

During my career I have been progressively zooming from large macroevolutionary scales to finer phylogenetic levels. This has forced me to confront what species are and how they originate. A significant amount of my work is now dedicated to systematics, speciation research and even taxonomy. To do so I use a combination of tools: reciprocal transplant experiments, measurement of various reproductive barriers, phylogenomics, population genetics, morphometrics.

My taxonomic contributions are focused  on the Alpine flora, where I have contributed to the description of the following species:

- Androsace delphinensis Dentant, Lavergne, F.C. Boucher & S. Ibanez

- Androsace saussurei Dentant, Lavergne, F.C. Boucher & S. Ibanez

- Androsace vesulensis Dentant, Lavergne, F.C. Boucher & S. Ibanez

A few representatives from the genus Argyroderma, endemic to quartz patches in the Knersvlakte, South Africa. This group is exceptionally diverse as it contains 11 species occuring on a single plain. Our work shows that multiple reproductive barriers act together to efficiently maintain species boundaries in this group. From left to right: A. framesii, A. pearsonii, A. testiculare, and A. theartii

Collaborators: Cédric Dentant, Camille Voisin, Tony Verboom, Allan Ellis, Laure Gallien, Sébastien Lavergne

Relevant publications: Boucher et al. 2024 Botanical Journal of the Linnean Society, Boucher et al. 2021 Scientific Reports, Boucher et al. 2017 New Phytologist, Boucher et al. 2016 Journal of Biogeography.


4) Models for the evolution of continuous traits on phylogenies

My empirical work on alpine plants has led me to investigate theoretical questions related to the evolution of traits over macroevolutionary timescales. In order to do so I have been developing new models in which traits evolve between hard bounds, either in a random way or under a deterministic force that can be of any shape. These models can be fitted to comparative data and compared to other already existing models using R code that we have developed.


Contrasted examples of trait evolution: the y-axis shows the value of a continuous trait, the x-axis shows time. Phylogenetic branching is pictured using different colors. A. Standard brownian motion. B. Bounded brownian motion, a model that we have recently developed to be fitted to phylogenetic comparative data.

Collaborators: Vincent Démery, Luke Harmon, Josef Uyeda, Tamara Münkemüller, Sébastien Lavergne, Wilfried Thuiller

Relevant publications: Verboom et al. 2020 Systematic Biology, Boucher 2019 Ecography, Boucher et al. 2018 Systematic Biology, Boucher & Démery 2016 Systematic Biology, Münkemüller et al. 2015 Functional Ecology,  Boucher et al. 2014 American Naturalist