Guilin Wu, Hainan Jianfengling Forest Ecosystem National Field Science Observation and Research Station, Research Institute of Tropical Forestry, Chinese Academy of Forestry, discusses his article: Shaded habitats drive higher rates of fern diversification
Ferns represent one of the three major lineages of vascular plants, having originated approximately 411–385 million years ago. In prehistoric times, they were a dominant group in the landscape and even served as a primary food source for some dinosaurs. Today, with over 10,000 extant species, ferns exhibit remarkable diversity and remain an essential component of the non-flowering plant world.
Most modern ferns are found in shaded, moist forests, either growing on tree canopies as epiphytes or beneath the forest floor as terrestrial species. Given this distribution, we were curious: could the shade habitats created by angiosperm forests have played a critical role in accelerating fern diversification?
To explore this question, we compared the diversification rates of sun- and shade-dwelling ferns and simulated how these rates changed over time. Our goal was to understand whether shaded environments, made possible by the rise of dense angiosperm forests, influenced the evolutionary success of ferns.
To achieve this, we first classified ferns based on their preferred habitats. We compiled data from the World Flora Online, a comprehensive plant database. Species were categorized as sun-dwelling if they were described as inhabiting “grassland,” “meadow,” “open areas,” “sunny spots,” or “forest margins.” Conversely, species found “under forest canopies,” “in dense forest,” or “in deep shade” were classified as shade-dwelling ferns.
With this classification in place, we applied phylogenetic techniques to analyze diversification patterns. Our findings were striking: shade-dwelling ferns exhibited significantly higher diversification rates compared to their sun-dwelling counterparts. Furthermore, since the emergence of dense tropical canopies, the diversification rate of shade-dwelling ferns has consistently surpassed that of sun-dwelling ferns. This suggests that the proliferation of angiosperms, which formed large, shaded forests, created ecological opportunities for ferns to diversify.
Our findings provide strong evidence that the expansion of shaded habitats, driven by the rise of flowering plants, played a crucial role in shaping the evolution of ferns. As angiosperm forests grew and provided stable, moist, and shaded conditions, ferns adapted and diversified to take advantage of these environments. This is a remarkable example of how changes in one group of plants (angiosperms) can directly influence the evolutionary trajectory of another (ferns).
In summary, our research highlights how the rise of shaded habitats created by angiosperm forests has been a key driver in the diversification of ferns. This study not only deepens our understanding of plant evolution but also underscores the intricate relationships between different plant lineages throughout Earth’s history.
