During my PhD at KU Leuven (Belgium, 2000–2005), I explored evolutionary and ecological patterns in the wood anatomy of flowering plants. As a postdoctoral researcher (2005–2010), I expanded my focus to functional anatomy, allowing me to link wood anatomical traits to drought tolerance. This integrative approach—combining detailed anatomical observations with ecophysiological insights—continued to evolve during my tenure-track period at Leiden University (2010–2014). It was also during this time that my long-standing fascination with the evolutionary origins of woodiness deepened. I became particularly interested in why some plants evolved woodiness from herbaceous ancestors. Many such species thrive in regions with recurring drought, suggesting that drought may have been a major evolutionary driver of wood formation across over 700 identified flowering plant lineages. Experimental drought studies on closely related species with varying degrees of stem lignification further support this idea: species with more lignified stems are more drought tolerant. Since joining Naturalis Biodiversity Center in 2014—first as a permanent researcher, then senior researcher in 2018, and group leader in 2020—I have continued to expand these research lines. Currently, I am planning a new project to build an open-access, AI-driven wood identification pipeline. By analysing images of thin wood sections, this tool aims to assist customs officers in detecting illegal logging much more efficiently than current methods allow. Since 2021, I have held a 30% appointment at the Institute of Biology Leiden (IBL), where I coordinate the Leiden Biodiversity Network (LBN) as part of a bridging role. LBN connects over 200 biodiversity researchers and stakeholders across Leiden University, Naturalis Biodiversity Center, the University of Applied Sciences, MBO Rijnland, and the municipality of Leiden. Leiden is uniquely positioned to grow into a leading hub for biodiversity research, thanks to a combination of strengths that distinguish LBN from other Dutch biodiversity research hubs. These include the presence of extensive living and natural history collections (Hortus botanicus, Naturalis), a wide range of biodiversity expertise fostering transdisciplinary collaboration, and the integration of fundamental research (e.g., evolution, biomonitoring) with applied approaches (e.g., living labs, nature restoration). Additionally, the active involvement of the municipal government in enhancing biodiversity in urban parks, canals, and surrounding landscapes—such as polders, dunes, tulip fields, and forests—provides a rich ecological context for research and innovation.

More information about Frederic Lens

Research

Studying rampant evolutionary transitions towards the woody growth form

The evolutionary transition from herbaceousness towards (phylogenetically) derived woodiness in flowering plants is a peculiar phenomenon dating back to Darwin's original observations. To understand why plants became woody and why this has happened so frequently during evolutionary history, we have compiled the first global derived woodiness database with about 7000 species belonging to 700 independent lineages across flowering plants. Most derived woody species thrive in continental regions with recurrent drought cycles. This has laid the foundation for our novel hypothesis, proposing drought as a major driver of the evolutionary transitions towards woodiness across most lineages. My team has already obtained preliminary experimental support for this hypothesis in several plant groups, and we are currently looking into alternative drivers of wood formation across flowering plants. 

Investigating anatomical traits underlying drought tolerance in plants

It is crucial to better understand how wild plants and crops respond to drought stress in a world facing global change. But we still do not know which set of traits regulate drought tolerance in a given species, and how this differs among species. Many studies have demonstrated that gas embolisms in the root-to-shoot water transport pipeline are a main reason why plants die when they face drought stress. This so-called hydraulic failure can spontaneously occur under drought stress, but some (drought-tolerant) species are much better adapted to avoid lethal levels of embolisms than other (more sensitive) species. We measure embolism resistance in stems, roots and leaves, along with other ecophysiological traits such as stomatal conductance, to estimate whole-plant drought tolerance. These experimental results can be compared across closely related species with contrasting differences in wood formation to assess the impact of stem lignification on drought tolerance.

Identification of traded timbers to fight illegal logging

With an estimated annual turnover of €50–150 billion, illegal logging is the third most profitable transnational crime, after drug trafficking and trade in counterfeit goods. The new European EUDR regulation, which aims to more strictly regulate international timber trade from 2025 onwards, will only be effective in protecting our forests if reliable, large-scale identification and origin-tracing methods are developed. At present, such global methods are not yet available, allowing illegal logging to continue to thrive. In collaboration with large wood collection institutes, we aim to develop a reliable, high-throughput wood identification pipeline based on images from wood anatomical sections to provide customs officers and other (non-)scientific stakeholders with a timber tracking tool that helps them identify illegally logged wood. Our efforts will lead to a freely accessible global wood identification tool that enables international and local authorities to enforce legal regulations, and will promote sustainable and environmentally responsible practices across the timber supply chain.

For more details, go to the website of my research group Functional Traits at Naturalis Biodiversity Center.

Collaborators:

Prof. Remko Offringa (IBL, Leiden University)

Dr. Sylvain Delzon (University of Bordeaux, France)

Prof. Steven Jansen (Ulm University, Germany)

Dr. Alex Zizka (Marburg University, Germany)

Teaching

Currently, I am involved in the Biology curriculum at Leiden University, where I teach a plant anatomy course in the first Bachelor (Biodiversity of Plants), and I lecture on woodiness transitions across major plant lineages at the Master level (Development and Evolution).

Publications