Shaded habitats drive higher rates of fern diversification

Modern ferns diversified simultaneously with the rise of angiosperms. This pattern is arguably the consequence of ecological opportunities presented by shady and moist habitats that emerged with the advent of angiosperm dominated habitats. This hypothesis was tested by applying phylogenetic comparative methods that investigated the role of shaded habitats in fern diversification across 1397 fern species from 37 families. Our results showed a significant positive correlation between the occupancy of shaded habitats and diversification rates across the phylogeny of ferns compared to those of open habitats with high sunlight. Tests evaluating false correlations using hidden state speciation and extinction corroborated this result. Since the onset of the Angiosperm Terrestrial Revolution, the diversification rates of shade-dwelling ferns has exceeded those of sun-dwelling ferns.

Synthesis: Our findings support the hypothesis that shaded habitats created by the flourishing of angiosperms resulted in the acceleration of fern diversification as a consequence of the successful colonization of shaded moist habitats in angiosperm dominated forests.