A new phylogeny of Rumex (Polygonaceae) adds evolutionary context to the diversity of reproductive systems present in the genus

Rumex is one of about 50 genera in the knotweed family, Polygonaceae. The genus comprises about 200 species with bisexual, or more commonly, unisexual flowers, with the species displaying monoecious, dioecious, synoecious (hermaphroditic) or polygamous reproductive systems. Some of the dioecious species have heteromorphic sex chromosomes, which is rare amongst angiosperms. We here present a plastid phylogeny of 67 species, representing all four subgenera. For this study, we used three chloroplast markers, rbcL, trnH-psbA, trnL-F and dense taxon sampling to reconstruct the most comprehensive molecular phylogeny of Rumex to date. The reconstructed phylogeny for this work resolves six major clades and one large grade in Rumex subg. Rumex. In addition, the species with known dioecious reproductive systems are resolved within a broader Bade we term the dioecious Bade. These results suggest that the species with divergent reproductive systems are more closely related to each other than to other species comprising the rest of the Rumex genus.

Automated summary

This study presents a plastid phylogeny of 67 species of Rumex, resolving their relationships and subgenus classification. It found that dioecious species are grouped within the same major clade, suggesting a closer relationship among species with different reproductive systems.