Phylogeny of Polycnemoideae (Amaranthaceae): Implications for biogeography, character evolution and taxonomy

• Published in: TAXON
• Main Authors: Masson, Rüdiger, Kadereit, Gudrun
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2013
• Subjects: Plant Science; Ecology, Evolution, Behavior and Systematics; Antarc*; Antarctica
• Online Access: http://dx.doi.org/10.1002/tax.621009; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Ftax.621009; https://onlinelibrary.wiley.com/doi/pdf/10.1002/tax.621009

Abstract Polycnemoideae is a poorly studied subfamily of the Amaranthaceae/Chenopodiaceae alliance which contains ca. 13 rare species in three disjunctly distributed genera. We present the results of a dated molecular phylogeny and a survey of morphology, micromorphology and stem anatomy revealing the phylogenetic relationships and historical biogeography of the subfamily as well as its morphological evolution. The results are converted into a new classification of the group. The divergence of Polycnemoideae from Amaranthaceae s. str. dates back to the Eocene and the oldest split in the subfamily separated a Northern Hemisphere lineage (Polycnemum) and a predominantly Southern Hemisphere lineage (Nitrophila, Hemichroa, Surreya gen. nov.) around the Eocene/Oligocene boundary. There is some evidence for a southern connection via Antarctica in the ancestor of the Nitrophila/Hemichroa/Surreya clade. The amphitropical genus Nitrophila likely originated in South America and reached North America via long–distance dispersal. Genera of Polycnemoideae diversified during the Miocene and Pliocene. They are species–poor and appear relictual. The morphological and micromorphological survey revealed a number of useful diagnostic characters which permit a clear definition of all four genera and 13 species recognized here. Hemichroa in its traditional circumscription lacks diagnostic characters. Hemichroa pentandra is much more similar to Nitrophila and shares a number of symplesiomorphies with it, while H. diandra and H. mesembryanthema, which form a highly supported clade, show several clear synapomorphic characters. Therefore the latter two species are here described within a new genus, Surreya R. Masson & G. Kadereit.