Data from: Modifications during early plant development promote the evolution of nature’s most complex woods

Secondary growth is the developmental process by which woody plants grow
radially. The most complex presentations of secondary growth are found in
lianas (woody vines) as a result of their unique demand to maintain stems
that can twist without breaking. The complex woody forms in lianas arise
as non-circular stem outlines, aberrant tissue configurations, and/or
shifts in the relative abundance of secondary tissues. Previous studies
demonstrate that abnormal activity of the vascular cambium leads to
variant secondary growth, however the developmental and evolutionary basis
for this shift is still largely unknown. Here, we adopt an integrative
approach, leveraging techniques from historically distinct
disciplines—developmental anatomy and phylogenetic comparative methods—to
elucidate the evolution of development of the complex woody forms in a
large lineage of tropical lianas, Paullinia L. (Sapindaceae). We find that
all forms of variant secondary growth trace back to the same modification
during early stem development, which results in young plants with lobed
stem outlines and a discontinuous distribution of vascular bundles. By
placing development in a phylogenetic context, we further show that the
lobed primary plant bauplan is the evolutionary precursor to all complex
woody forms in the Sapindaceae lianas. We find evidence for three
evolutionary mechanisms that generate phenotypic novelty: exaptation and
co-opting of the ancestral bauplan; the quasi-independence of the
interfascicular and fascicular cambia; and the inclusion of additional
developmental stages to the end of the ancestral ontogeny. Our study
demonstrates the utility of integrating developmental data within a
phylogenetic framework to investigate the evolution of complex traits.