Two new species of Rhipidoglossum (Orchidaceae: Angraecinae) from Tanzania and Zimbabwe
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ISSN: 0075-5974 (print) ISSN: 1874-933X (electronic)
Two new species of Rhipidoglossum (Orchidaceae: Angraecinae) from Tanzania and Zimbabwe João N. M. Farminhão1,2
& Phillip J. Cribb3
Summary. Two new species of angraecoid orchid from East and South-central Africa are described and illustrated.
Rhipidoglossum lucieae is known from the Eastern Arc Mountains of Tanzania (West Usambaras) and has been misidentified as R. pulchellum in previous floristic treatments. Rhipidoglossum philatelicum is reported from the Eastern Highlands of Zimbabwe (Bvumba and Chimanimani Mts) and has been misclassified under R. subsimplex. Distribution maps and the conservation status of these two novelties are provided. Future directions in epiphytic orchid species discovery in eastern tropical Africa are proposed. Key Words. Diaphananthe, Eastern Arc Mountains, Eastern Highlands, epiphyte, taxonomy, Usambaras, Vandeae.
Introduction With approximately 50 species, Rhipidoglossum Schltr., after a recently proposed re-circumscription (Farminhão et al. 2018), ranks as one of the most species-rich angraecoid genera in continental Africa. For a long time, this genus had been regarded as a section of Diaphananthe Schltr. but molecular phylogenetics and different morphological traits indicate that the two genera should be kept separate (Cribb 2014; Simo-Droissart et al. 2018). This genus of epiphytic orchids is characterised by a column with a trilobed, non-papillate rostellum with a mid-lobe more prominent than lateral lobes, alongside a pollinarium with two, separate, saddle-shaped viscidia, and an undivided lip (Farminhão et al. 2018). Within the framework of an ongoing monographic treatment of Rhipidoglossum, carried out by the first author, some specimens identified as R. xanthopollinium (Rchb.f.) Schltr., and as R. pulchellum (Summerh.) Garay var. pulchellum from Tanzania, and previously cited in the Flora of Tropical East Africa (Cribb 1989), were found to correspond to an undescribed species of this genus. Additionally, specimens labelled as R. subsimplex (Summerh.) Garay from Zimbabwe referenced in Flora Zambesiaca (la Croix & Cribb 1998) were redetermined as belonging to another novelty. In this paper, both new species are described and illustrated, and their conservation status, following IUCN red list categories, are preliminarily assessed.
Finally, some brief biogeographical notes are presented and future directions in the discovery of orchid species in tropical Africa are proposed.
Materials and Methods Herbarium specimens associated with the two new taxa, as well as morphologically similar species of Rhipidoglossum, were examined in detail at BM, BR, BRLU, K and P (abbreviations according to Thiers (2019, continuously updated)). Flowers of dried specimens were rehydrated using boiling water and examined in Copenhagen mix. Flowers preserved in spirit (Kew mix/Copenhagen mix) were also examined. Comparative measurements and studies of the details of column morphology were made with a Zeiss Stemi SV11 stereo microscope. Characters o
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