Clarifying generic delimitation in Nyctaginaceae tribe Pisonieae after more than a century of taxonomic confusion

After more than a century of taxonomic confusion in Nyctaginaceae tribe Pisonieae, we aim to clarify relationships in the tribe by analysing combined sequences of nuclear ribosomal ITS and plastid intron rps16 using phylogenetic analyses based on parsimony and Bayesian inference and performing ancestral character estimates of morphological traits traditionally used in the tribe. Results could be used as the basis for taxonomic restructuring of this notoriously complicated group, suggesting that Pisonieae are subdivided into three distinct lineages, clades A, B and C. Clade A comprises species with pedicellate flowers of Pisoniella, Pisonia section Prismatocarpae and P. section Timeroya, and clades B and C comprise species with sessile flowers of P. section Pisonia (clade B) and P. section Paucistaminatae (P. sandwicensis), Guapira and Neea (Clade C). In addition, results indicate that exserted stamens are highly homoplastic in the Guapira/Neea lineage, whereas dry anthocarps with conspicuous glandular emergences are ancestral in Pisonieae. We recommend that Pisonia should be recircumscribed to correspond to clade B, which includes the type species of the genus (although the topology would also allow for recognition of Pisonia s.l.). Neea should be synonymized under Guapira. Ceodes and Rockia merit generic resurrection.