Notes on Isoglossinae (Acanthaceae) in Madagascar, with four new species of Isoglossa.

Current generic delimitation in subtribe Isoglossinae of Acanthaceae is discussed using available morphological and molecular data. Particular consideration is given to the small genera endemic to Madagascar — Benoist, S.Moore, Benoist and the illegitimate Benoist — and how these relate to the current circumscription of Oerst. The relative merits and challenges of recognising a broadly circumscribed are considered. s.l. is readily recognisable by combining a bilabiate corolla, with an androecium comprising two bithecous stamens and lacking staminodes, and with the presence of gürtelpollen (i.e. bipororate pollen, circular in apertural view and with a pronounced interapertural “girdle” of tectate exine), whilst the segregate genera as currently defined are not separable morphologically. However, the limited molecular phylogenetic data available to date indicate that s.l. is paraphyletic. Pending further molecular studies of this group to clarify generic delimitation, it is proposed that all new taxa in bithecous Isoglossinae should be described in as an interim solution Four new species of are described: Onjalal. & I.Darbysh., I.Darbysh. & Phillipson, I.Darbysh. and I.Darbysh. & Callm., the lattermost of which is based on Benoist nom. illegit. In addition, Benoist (including Benoist) and T.F.Daniel, Letsara & Martín-Bravo are transferred to , and three names within L. are synonymised within existing taxa in Isoglossinae. Lectotypes are selected for Benoist, Benoist and Benoist (= Benoist var. Benoist).