Data from: Evolution of a CAM anatomy predates the origins of Crassulacean acid metabolism in the Agavoideae (Asparagaceae)

Crassulacean acid metabolism (CAM) is a modified form of photosynthesis
that has arisen independently at least 35 times in flowering plants. The
occurrence of CAM is often correlated with shifts to arid, semiarid, or
epiphytic habits, as well as transitions in leaf morphology (e.g.
increased leaf thickness) and anatomy (e.g. increased cell size and
packing). We assess shifts between C3 and CAM photosynthesis in the
subfamily Agavoideae (Asparagaceae) through phylogenetic analysis of
targeted loci captured from the nuclear and chloroplast genomes of over 60
species. Carbon isotope data was used as a proxy for mode of
photosynthesis in extant species and ancestral states were estimated on
the phylogeny. Ancestral character state mapping suggests three
independent origins of CAM in the Agavoideae. CAM species differ from C3
species in climate space and are found to have thicker leaves with densely
packed cells. C3 ancestors of CAM species show a predisposition toward
CAM-like morphology. Leaf characteristics in the ancestral C3 species may
have enabled the repeated evolution of CAM in the Agavoideae subfamily.
Anatomical changes, including a tendency toward 3D venation, may have
initially arisen in C3 ancestors in response to aridity as a way to
increase leaf succulence for water storage.