Infra-familial phylogeny of Urticaceae, using chloroplast sequence data

Abstract

Recent studies of the phylogeny of the Urticales have suggested that Cecropiaceae, at least in part, should be included within Urticaceae. To evaluate phylogenetic relationship between these two taxa, together with the consequences on tribal concepts (of the Urticaceae) of including any part of Cecropiaceae within Urticaceae, we analysed sequence variation for larger databases of both rbcL and trnL-F sequences. We conclude that the circumscription of Urticaceae needs to be broadened to include taxa of Cecropiaceae, with Urticeae here expanded to include Poikilospermum. The tribal placement of Cecropia and Coussapoa (both Cecropiaceae) remains unclear but their affinities are with the Forsskaoleeae, Parietarieae and Boehmerieae. The circumscription of Boehmerieae should be changed to exclude Myriocarpa, with the latter genus exhibiting a strong relationship with Elatostemeae. The intratribal structure of the Elatostemeae is unclear because of the uncertainty of the position of Myriocarpa, but there is a strong suggestion that the tribe consists of two sister taxa, one of Elatostemeae sensu stricto, including Elatostema and Procris, and the other consisting of Lecanthus and Pilea. It is reconfirmed that Pellionia should not be recognised as a distinct genus and is here regarded as a synonym of Procris, rather than part of the synonymy of Elatostema, as previously suggested. Boehmeria, Cypholophus and Laportea as currently circumscribed are all paraphyletic. There are three evolutionary lineages in the Urticaceae revealed by our study, namely (1) Boehmeriea–Cecropieae–Forsskaoleeae–Parietarieae, (2) Urticeae and (3) Elatostemeae.