Taxonomic notes and novelties in the genus Isoglossa (Acanthaceae) from east Africa

Summary: A review of the genus Isoglossa Oerst. in east Africa is presented in preparation for the FTEA Acanthaceae treatment. Variation in pollen type within the African Isoglossa is summarised and its implications for generic circumscription are considered. The occurrence of periodic gregarious monocarpy (a plietesial life cycle) within Isoglossa is reviewed, with reference to other occurrences of this phenomenon in the Acanthaceae. The relationship of African taxa of Isoglossa to the Asian I. dichotoma (Hassk.) B. Hansen is reviewed and a tabular synopsis and key are presented for this group in east Africa, together with the description of three new species (I. paucinervis, I. ventricosa, I. bondwaensis), one new subspecies (I. membranacea subsp. septentrionalis) and one new name (I. bruceae) within the group. A further three new east African species (I. variegata, I. faulknerae, I. multinervis) and one new subspecies (I. substrobilina subsp. tenuispicata) are described, and the status of I. salviiflora in relation to I. floribunda is reassessed. The conservation status of each taxon is considered. © The Board of Trustees of the Royal Botanic Gardens, Kew, 2009.