Research Article |
Corresponding author: Marie Claire Veranso-Libalah ( mario_clario@yahoo.ca ) Academic editor: Ricardo Kriebel
© 2017 Marie Claire Veranso-Libalah, Robert Douglas Stone, Gudrun Kadereit.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Veranso-Libalah MC, Stone RD, Kadereit G (2017) Argyrella richardsiae, a new species of Melastomataceae from the wet miombo woodlands of south-central Africa. PhytoKeys 82: 113-121. https://doi.org/10.3897/phytokeys.82.12914
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A new species from the wet miombo woodlands of Tanzania and Angola, Argyrella richardsiae Veranso-Libalah & G.Kadereit, sp. nov. (Melastomataceae, Melastomateae), is described and illustrated. Although the widespread Argyrella canescens also occurs in Tanzania and northeastern Angola, A. richardsiae is morphologically most similar to Argyrella bambutorum known only from the Northwest of Cameroon, but differs by its indumentum of glandular trichomes on the entire plant (versus a mixture of stellate and glandular trichomes in other species of Argyrella), leaf-blades with serrulate margins (versus entire margins in A. bambutorum) and lateral nerves that become faint mid-way and never reach the leaf apex (versus conspicuous lateral nerves percurrent from the base to the apex in A. bambutorum). A preliminary conservation status of Endangered (EN) is proposed for A. richardsiae following the IUCN Red List Categories and Criteria. A taxonomic key and distribution map of all Argyrella species is also included.
Africa, Angola, Argyrella , Dissotis , Heterotis , Melastomataceae , new species, Tanzania
Argyrella Naudin was first described by
A recent molecular phylogenetic analysis of African Melastomateae by
From our comparative study of herbarium collections through visits (BR and BRLU), loans (BR, BRLU, C, EA, MO, NHN, KEW and UPS), and online repositories: BM (http://data.nhm.ac.uk/), P (https://science.mnhn.fr/all/search), LISC (http://actd.iict.pt/) and COI (https://www.uc.pt/herbario_digital/catalogues), we have identified a wet miombo woodland species of Argyrella from Tanzania and Angola that is new to science, described and illustrated herein. All measurements were taken from dried specimens. The extent of occurrence (EOO) and area of occupancy (AOO) were calculated using GeoCAT (
TANZANIA. Katavi region: Mpanda district, 19 km on Mpanda-Uvinza road, seepage areas in tall Julbernardia paniculata, Terminalia mollis woodland, grey and sandy soils, 6°14'S, 30°59'E, 1100 m, 14 May 1997 (fl & fr) , S. Bidgood, D. Sitoni, K. Vollesen & C. Whitehouse 3935 (Holotype: K! [K000771858!]; isotypes: K! [K000771858!]; BR! [BR0000013189358!], C!, EA!, P! [P05222349!]).
The new species differs from all other species of Argyrella by having only glandular trichomes throughout the whole plant (versus a mixture of stellate and glandular trichomes in the other species), secondary branches arising at each node and leaves generally pointing downwards. It resembles A. bambutorum (Gilg & Ledermann ex Engl.) Veranso-Libalah & G.Kadereit but differs by having leaf-blades with serrulate margins (versus entire margins in A. bambutorum) and the primary pair of lateral nerves disappearing half-way between the base and the apex (versus conspicuous lateral nerves percurrent from the base to the apex in A. bambutorum). Argyrella richardsiae also differs from the widely distributed A. canescens and the Angolan endemic A. angolensis (Cogn.) Veranso-Libalah & G.Kadereit by having many new branches or buds arising at each node (versus unbranched herb in A. angolensis and A. canescens) and leaves sessile with amplexicaul bases generally pointing downwards (versus leaves petiolate with rounded to cordate bases and generally pointing upwards in A. angolensis and A. canescens) and only glandular trichomes on the hypanthium (versus dense stellate and glandular trichomes on the hypanthium of A. angolensis and A. canescens).
Erect herb up to 1 m tall with branches arising at each node (Fig.
ANGOLA. Huambo province: Longonjo, Lépi, Caála 1700m, 3 August 1940, (fr), J. Gossweiler 12147 (LISC030751!, LISC030752!, LISC030753!, LISC030754!, LISC030755!, LISC030756!). TANZANIA. Mpanda district: Uruwira-Tabora road, Brachystegia woodland, Kambisama river, 1400 m, 30 September 1970 (fl & fr), Mrs H.M. Richards & S. Arasululu 26190 (K!, BR!); Mlele beekeeping reserve, riverine woodland, Iloba river, 6°47'56"S, 31°37'33"E, 1562 m, 7 May 2004, N.A. Mwangulango 1193 (MO, MJG!).
The species epithet is in honour of Mary Alice Eleanor Richards (also known from her collection labels as Mrs H.M. Richards), who collected extensively in Africa from 1951 to 1974 (Polhill and Polhill 2015). Of our new species Argyrella richardsiae, she made a collection which is cited above in ‘Additional specimens examined’.
This species is evidently endemic to the wet miombo woodlands of Mpanda district, southwestern Tanzania and Huambo province, central Angola (Fig.
Proposed IUCN Red List Category: Endangered (EN): B2ab (ii,iii) EOO ~79 km2, AOO 32 km2. This species is only known from four collections in seepage, marshes or riverine woodlands (wet miombo woodlands) of the Mpanda district, Tanzania and Huambo province of Angola. Although cited on the collection label Mwangulango 1193 as a locally frequent herb in the Mpanda district, it is still a poorly collected species. As earlier suggested, A. richardsiae may also occur in wet miombo woodlands of southern DRC, northern Zambia and southern Malawi, but at the moment we think it is better to treat it as endangered until we are certain that this species is found in other places. Moreover, this species is only known from one collection in Angola since 1940. Generally, miombo woodlands are an important source of livelihood because they provide social, economic, and environmental benefits such as firewood, timber, medicinal plants, food, and catchment protection, among others. According to
Argyrella richardsiae is similar to A. bambutorum but differs by having serrulate leaf margins, intersepalar appendages absent, and stamens dimorphic (versus entire leaf margins, intersepalar appendages present, and stamens isomorphic in A. bambutorum). The new species also differs from A. amplexicaulis, A. sessilis (Hutch. ex Brenan & Keay) Veranso-Libalah & G.Kadereit and A. angolensis by its many new branches or buds arising at each node (versus unbranched in A. amplexicaulis, A. sessilis and A. angolensis). Argyrella richardsiae has broadly ovate leaves versus lanceolate to linear in Argyrella canescens and A. linearis (Jacq.-Fél.) Veranso-Libalah & G.Kadereit. Also, A. richardsiae has only glandular trichomes on the entire plant and leaves generally pointing downwards versus a mixture of stellate and glandular trichomes with leaves pointing upwards in the other species.
1 | Leaf lamina ovate to broadly ovate, base sessile and amplexicaul or subsessile (petiole < 2 mm long) | 2 |
– | Leaf lamina linear or lanceolate-oblong, petiolate (petiole > 2 mm long) | 5 |
2 | Leaves subsessile; intersepalar appendages present; stamens yellow, subequal in size (isomorphic) (Northwest region of Cameroon) | A. bambutorum |
– | Leaves sessile to amplexicaul; intersepalar appendages absent; stamens markedly unequal in both size and colour (dimorphic) | 3 |
3 | Sparingly branched herb; leaf margins entire; principal pair of lateral nerves conspicuous and reaching the apex on the adaxial surface; calyx-tube and stems with stellate-tomentose and glandular trichomes | 4 |
– | Much branched herb with buds and branches at each node; leaf margins serrulate; principal pair of lateral nerves fading half-way between the base and the apex on the adaxial surface; calyx-tube and stems with glandular trichomes only (Angola and Tanzania) | A. richardsiae |
4 | Leaf lamina ovate to ovate-lanceolate, < 1 cm wide; calyx-tube with sparse and short stellate trichomes (Guinean region) | A. amplexicaulis |
– | Leaf lamina broadly ovate, > 1.5 cm wide; calyx-tube with dense stellate-tomentose trichomes (Sierra Leone) | A. sessilis |
5 | Internodes < 2 cm long; leaves linear, the pair of lateral nerves situated very close to the margins; calyx-tube with simple trichomes; intersepalar appendages absent (Guinea) | A. linearis |
– | Internodes > 2 cm long; leaves oblong-lanceolate, the principal nerves 5–7 in number; calyx-tube with simple setose and short stellate trichomes sometimes mixed with glandular trichomes; intersepalar appendages present | 6 |
6 | Reticulate secondary venation of the leaves invisible beneath; calyx-tube campanulate, non-glabrescent with age; intersepalar appendages subulate-filiform (Angola) | A. angolensis |
– | Reticulate secondary venation of the leaves visible beneath; calyx-tube ovoid-subspherical, glabrescent with age; intersepalar appendages shortly subulate or absent (widespread in Africa) | A. canescens |
We are grateful to the curators and personnel of the following herbaria (BR, BRLU, C, EA, MO, WAG, K and UPS) for providing loans and assistance during visits. We are also thankful to Nina Davies for scanning and sending images of the new species from K. We would also like to thank Doris Franke for preparing the illustration. We are also grateful to Ricardo Kriebel, Fabian Michelangli and an anonymous reviewer for their useful comments and suggestions. This study is part of a larger project on African Melastomateae which is supported by the International Association for Plant Taxonomy (IAPT), German Research Foundation (DFG) project number KA1816/10-1, Equal opportunity travel grant, University of Mainz, Germany, the German Academic Exchange Service (DAAD) and the Feldbauschstiftung.