On the morphological position of Paepalanthus subgenus Psilandra (Eriocaulaceae)

Paepalanthus subgen. Psilandra comprises two species known only from the type collections. The aim of this study is to evaluate their unique floral morphology within a given phylogenetic context and its implications for taxonomy. Flowers of both species were analyzed, described, and photographed using a digital microscope. Taxonomically relevant characters were mapped on previous molecular phylogenies. The flowers of both species fit the Paepalanthoideae pattern and are quite similar to each other. The petals of the pistillate flowers, although free, show evidence of previous fusion in the middle. The free condition is interpreted to be secondary, probably because of the handling of the specimens or to the current developmental stage. Character mapping indicates that both species share floral features with Syngonanthus but not with Paepalanthus. Therefore, based on the median fusion of the pistillate flower petals, absence of floral bracts, petals of the pistillate flower being shorter than the sepals, simple stigmas in the commissural position, the pedicellate pistillate flower, and the glabrous petals and sepals, we transfer P. subgen. Psilandra to synonymy of Syngonanthus sect. Syngonanthus and combine both species in this genus.