Why plants became woody during evolutionary history? As an evolutionary biologist, I am fascinated to understand the frequent habit transitions towards the woody growth form during evolutionary history of flowering plants.
This long-standing evolutionary phenomenon dates back to Darwin's original observations, and is known in the literature as insular woodiness (see picture) or derived woodiness. I have compiled a database with nearly 7000 derived woody species of flowering plants, showing that most of these species are native to dry continental vegetation types. Evolutionary transitions towards derived woodiness have evolved at least 600 times independently, which raises the intriguing question which environmental factors triggered wood formation in all these lineages. To further unravel wood formation, I am applying a combined approach linking models of evolution and ecology with experimental work focusing on water transport measurements within stems. Results so far have highlighted drought as a main potential driver for woodiness in various derived woody lineages, especially on continents, but other environmental variables most likely have impacted wood formation as well.