ISSN 1179-3155 (print edition) Phytotaxa 306 (1): 091–095 http://www.mapress.com/j/pt/ Copyright © 2017 Magnolia Press Article PHYTOTAXA ISSN 1179-3163 (online edition) https://doi.org/10.11646/phytotaxa.306.1.8 A new species of Craterostigma (Linderniaceae) from Kenya IAIN DARBYSHIRE1 & EBERHARD FISCHER2 1 Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB, United Kingdom; e-mail: i.darbyshire@kew.org Institut für Integrierte Naturwissenschaften – Biologie, Universität Koblenz-Landau, Universitätsstraße 1, 56070 Koblenz, Germany; e-mail: efischer@uni-koblenz.de 2 Abstract The new species Craterostigma loitense from the Loita Hills in Kenya is described and illustrated. It differs from Craterostigma purpureum in the two abaxial staminodes, the basal tufts of hairs on the anthers, and the subentire to serrulate leaf margin. Introduction The family Linderniaceae (Lamiales) has been recently separated from the traditional Scrophulariaceae (Rahmanzadeh et al. 2005). Molecular and morphological studies have shown that Lindernia Allioni (1766: 178) in the broader sense, usually accepted by most recent authors (e.g. Pennell 1935, Fischer 1992, 1999, Philcox 1990, 2008), is polyphyletic and comprises several clades, with seed type being an important apomorphy (Fischer et al. 2013). The seeds of Linderniaceae can be divided into three different types: bothrospermous, aulacospermous and non-alveolated. In bothrospermous seeds the surface is sculptured due to the pit-like ingrowth of the inner epidermis of the ovule integument, the endothelium, into the endosperm. This endosperm alveolation results in characteristic rounded pits on the seed surface. By fusion of several endosperm pits, longitudinal furrows are produced that are typical of the aulacospermous seed type. In the non-alveolated seeds, the surface of the endosperm shows 5–6 rib like shallow longitudinal furrows but no deeply impressed pits or ditch-like furrows (Fischer 1992). According to Fischer et al. (2013), Lindernia s.str. has non-alveolate seeds while the clades with bothrospermous seeds comprises the genera Torenia Linnaeus (1753: 619), Craterostigma Hochstetter (1841: 668) in a broad sense, Bonnaya Link & Otto (1821: 25), Vandellia Linnaeus (1767: 384, 422) and Linderniella Fischer et al. (2013: 227). The clade with aulacospermous seeds consists of Crepidorhopalon Fischer (1989: 443), Hartliella Fischer (1992: 204), and Bampsia Lisowski & Mielcarek (1983: 377). Tropical Africa is a centre of diversity for Linderniaceae, where more than 90 species have been recorded (Fischer 1992, 1999, Fischer & Lachenaud 2013, Fischer et al. 2014). Tropical East Africa is a particularly species-rich region, with at least 45 recorded taxa (Ghazanfar et al. 2008). The members of Craterostigma s.str. can easily be recognized by the usually rosulate, Plantago-like habit with truncate synflorescence bearing only axillary flowering shoots sometimes reduced to a single flower. However, the only autapomorphy of Craterostigma s.str. is the red to yellow-orange color in the intercellular spaces of the root cortex (Fischer 1992). The more broadly defined Craterostigma is a well-supported monophyletic clade and includes taxa with basal rosulate leaves and sterile abaxial staminodes, e.g. C. engleri Fischer et al. (2013: 222), C. yaundense (Moore 1919: 216) Fischer et al. (2013: 223), C. gossweileri (Moore 1919: 215) Fischer et al. (2013: 222), as well as taxa with elongate stems and well developed main inflorescence bearing flowers with usually 4 fertile stamens. During research for a revised edition of his Upland Kenya Wild Flowers (Agnew 2013), Andrew Agnew collected a remarkable specimen of Linderniaceae from Loita which proved to be a new species of Craterostigma, based on the characteristic rosulate habit and single-flowered axillary inflorescences held above the leaf rosette. This taxon is morphologically close to Craterostigma purpureum Lebrun & Toussaint in Robyns (1943: 83) but differs in the adaxial stamens being reduced to sterile staminodes and the fertile anthers bearing long hairs at the base. The present study is based on the investigation of dried specimens. The type specimen comprises four wildcollected individual plants with both flowers and fruits present. Floral dissections were made on flowers from plants grown on from seed by Andrew Agnew. Accepted by Christian Bräuchler: 11 Apr. 2017; published: 5 May 2017 91 Craterostigma loitense I.Darbysh. & Eb.Fisch. sp. nov. (Fig. 1) Lindernia sp. A (“loitensis”) sensu Agnew (2013: 300, pl. 115). Type:—KENYA. Loita Hills, Enkang Sapuk Camp, on ridge above Entesakerra, 2300 m, 20 June 2009, A.D.Q. Agnew & J. Agnew s.n. (holotype EA000004205!). Craterostigma loitense differs from C. purpureum in the leaf margin subentire to minutely serrate (vs. entire), in the two abaxial staminodes with minute rudimentary anthers (vs. fertile), and in the anthers of the fertile stamens with basal tuft of long hairs (vs. hairs lacking). Subrosulate dwarf annual herb, leaves clustered between very short internodes, sometimes with a longer trailing internode 11 mm long between leaf clusters. Stems 4-angular, puberulous, hairs blunt-tipped. Leaves subsessile or with flattened petiole to 3 mm long; blade somewhat fleshy, adaxial surface green, abaxial surface often purple, at least towards apex, ovate to narrowly so or elliptic, 6.5–11 × 2.5–4.7 mm, base attenuate, margin subentire or minutely serrate, apex narrowed into an acute or blunt tip; midrib prominent, lateral veins inconspicuous; young leaves minutely puberulous, later glabrescent. Inflorescences axillary with flowers usually held well above the leaf rosettes; flowers solitary, ebracteolate; pedicels 4–12 mm long or rarely shorter in flower, extending to 11–22 mm long in fruit, indumentum as stems. Calyx green with purple lobes or purple extending to near the base, 3.0–4.5 mm long in flower, extending to 4–5 mm long in fruit, shortly and unevenly 5-lobed, longest (adaxial) lobe 1.0–2.2 mm long, shortest (abaxial) pair of lobes 0.4–1.25 mm long, sparsely puberulous mainly along midrib of each lobe and towards lobe apices. Corolla white with purple streaking on the limb, bilabiate; tube held erect, cylindrical, 3.0–3.3 mm long, c. 1.5 mm in diameter; lips 3.0–3.4 mm long when flattened; upper lip hooded, triangular-attenuate from broad base, 3.0–3.4 mm wide at base, apex shortly bilobed; lower lip with three rounded lobes 1.5–1.7 mm long with irregular margin, palate minutely puberulous centrally and extending into throat. Stamens two, adaxial, attached at base of upper lip, filaments 0.7–1.1 mm long, convergent, the divergent anther thecae forming a cross-shape, thecae 0.6–0.7 mm long, lower theca of each stamen with a basal tuft of long hairs; staminodes two, abaxial, attached on palate of lower lip, geniculate with a swollen yellow-puberulous boss and a recurved filament together up to 1.5 mm long when flattened, apex with a vestigial anther up to 0.25 mm long. Pistil glabrous; ovary oblong, ± 2 mm long; style slender, ± 2 mm long; stigma of two broad membranous lobes, ± 0.75 mm in diameter; disc annular but with one side incomplete. Capsule elongate, (5.0–) 8.5–12.0 × 1.5–2.5 mm, glabrous; seeds ± 0.5 × 0.4 mm, bothrospermous, with longitudinal ribs and finer transverse ribs. Distribution:—Southern Kenya (Flora of Tropical East Africa region K6), only known from the type locality. Etymology:—Named after the type locality of the Loita Hills. Habitat and Ecology:—Shallow soils on quartzitic rocks at 2300 m elevation, growing under the edges of tall plants. The species is reported as poikilohydric (Agnew 2013). Conservation status:—Craterostigma loitense is only known from the type collection. The area where it occurs is grazed and trampled, which may help to maintain the open habitat the plants require, although the substrate is so nutrient-poor that this may also limit dense woody growth (A.D.Q. Agnew, pers. comm.). As the specimens of C. loitense are so tiny, they could easily be overlooked and may well occur at other sites in the Loita Hills and beyond. In the light of the limited distribution, population and threat data on this species, it is provisionally assessed as DD (Data Deficient), following the Categories and Criteria of IUCN (2012). Taxonomic notes:—Craterostigma loitense appears from morphological evidence to be most closely allied to C. purpureum from the Democratic Republic of the Congo. However, it clearly differs in having the combination of a subentire to minutely serrate leaf margin, the two abaxial staminodes having minute rudimentary anthers and in the anthers of the fertile stamens having a basal tuft of long hairs, whilst in C. purpureum, the leaves are entire, the abaxial stamens are fertile and the anthers are glabrous. Within its range, it superficially resembles Linderniella pulchella (Skan in Hemsley & Skan 1906: 348) Fischer et al. (2013: 227) in general habit and leaf shape, but differs in the truncate inflorescence with single long-pedicelled flowers in the axils of the basal rosulate leaves while L. pulchella has a main stem with a racemose inflorescence bearing bracts with axillary flowers above the basal rosulate leaves. Furthermore the abaxial staminodes lack any anther vestiges in L. pulchella, and the fertile anthers lack the basal tuft of hairs. The only other African Linderniaceae bearing a tuft of hairs at the base of the anthers are Craterostigma engleri and C. gossweileri from Angola and C. yaundense from Cameroon, all growing on granitic rock outcrops. They share with C. loitense the basal rosulate leaves and the lack of a main inflorescence, but all three differ from it in the axillary inflorescence always having a distinct long peduncle bearing bracts with axillary flowers, the corolla being bluish, and the sterile abaxial staminodes being geniculate or clavate and lacking an anther vestige (Fischer 1992). 92 • Phytotaxa 306 (1) © 2017 Magnolia Press DARBYSHIRE & FISCHER FIGURE 1.—Craterostigma loitense. A–D: habit, A & D in flower, B & C in fruit; E & F: dissected corollas; G: calyx dissected to show pistil; H & I: abaxial staminodes with vestigial anthers; K: detail of fertile anther from adaxial stamen. Drawn by E. Fischer, A from photograph of living material, B–K from the holotype (A.D.Q. Agnew & J. Agnew s.n.). A NEW SPECIES OF CRATEROSTIGMA (LINDERNIACEAE) Phytotaxa 306 (1) © 2017 Magnolia Press • 93 Additional specimens examined:—Hort. A.D.Q. Agnew, August–September 2010, A.D.Q. Agnew s.n. (EA!). Craterostigma purpureum Lebrun & Toussaint in Robyns (1943: 83)—D.R.CONGO. Parc National de Virunga, May ya moto, savane au bord de la Rutshuru, July 1937, Lebrun 6919 (holotype BR!); plaine de la Rusizi, region de Luberizi, Mt. Kalambo, 24 February 1950, Germain 6280 (BR!); plaine de la Rusizi, Bulamata, March 1950, Germain 663 (BR!). Acknowledgements We thank the Directors of the following herbaria for the possibility to study specimens (acronyms according to Holmgren et al. 1990): BR, EA and K. Special thanks go to Dr. Andrew Agnew who provided the specimen and photographs of the new taxon and useful information on the type locality. We thank the subject editor, Dr. Christian Bräuchler, and an anonymous reviewer for their helpful comments on a draft of the manuscript. References Agnew, A.D.Q. (2013) Upland Kenya Wild Flowers and Ferns: a flora of the flowers, ferns, grasses and sedges of highland Kenya. Third Edition. 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