South African Journal of Botany 124 (2019) 20–22 Contents lists available at ScienceDirect South African Journal of Botany journal homepage: www.elsevier.com/locate/sajb Zygotritonia atropurpurea (Iridaceae: Crocoideae), a new local endemic species from northern Zambia of this small tropical African genus P. Goldblatt a,b,⁎, J.C. Manning b,c, N. Wightman d, W. McCleland e a Missouri Botanical Garden, P.O. Box 299, St. Louis, MO 63166, USA Research Centre for Plant Growth and Development, School of Life Sciences, University of KwaZulu-Natal, Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa Compton Herbarium, South African National Biodiversity Institute, Private Bag X7, Claremont 7735, South Africa d Homegarden Landscape Consultants Ltd., Private Bag 30C, Chilanga, Lusaka, Zambia e ECOREX Consulting Ecologists, PostNet Suite 192, Private Bag X2, Raslouw 0109, Gauteng, South Africa b c a r t i c l e i n f o Article history: Received 28 January 2019 Received in revised form 8 March 2019 Accepted 17 April 2019 Available online xxxx Edited by GV Goodman-Cron Keywords: Africa New species Phylogeny Taxonomy Watsonieae a b s t r a c t A seventh species of the tropical and sub-Saharan African genus Zygotritonia Mildbr. has recently been discovered in northern Zambia. It is distinct in the genus in its tall stature, sometimes exceeding 1.3 m, and multibranched spike bearing numerous relatively small, dark purple flowers. The new species, here described as Z. atropurpurea Goldblatt & J.C.Manning, broadly conforms to other species of the genus in its pleated foliage leaf or leaves, zygomorphic flowers with a large, arching dorsal tepal and smaller upper lateral and lower tepals, the three lowermost directed downward and with spooned tips. Known by both morphological comparison and DNA sequence analysis to be a member of tribe Watsonieae of Crocoideae, Zygotritonia is allied to the Lapeirousia Pourr. group of genera, specifically Savannosiphon Goldblatt & Marais and Cyanixia Goldblatt & J.C.Manning. © 2019 SAAB. Published by Elsevier B.V. All rights reserved. 1. Introduction The tropical and sub-Saharan African genus Zygotritonia Mildbr. (1923) (Iridaceae) now includes seven species of herbaceous geophytes (Goldblatt, 1989; Goldblatt et al., 2015). It is distinguished within subfamily Crocoideae by the typically pleated leaves (sometimes linear or terete) and relatively small, zygomorphic flowers with the dorsal tepal largest and strongly arched, the lower tepals spathulate and spooned at the tips, and the style with extremely short branches or apparently undivided. Its relationships within the subfamily have been established to lie with tribe Watsonieae where its corm of axillary origin is consistent with tribes Tritoniopsideae and Watsonieae, whereas the remaining tribes in the subfamily have corms of axial origin (Goldblatt and Manning, 2008; Goldblatt et al., 2016). The coarsely fibrous, shaggy corm tunics likewise accord with some members of these two tribes. The inner floral bracts are typically bilobed and apically notched, and sometimes shorter than the outer, thus consistent with Watsoniaeae but the weakly divided (or undivided) style is not. Most genera and species of Watsonieae have well-developed style branches that are in turn usually divided for half their length. The style branches in Tritoniopsideae are undivided. Zygotritonia is taxonomically well studied (Goldblatt, 1989; Goldblatt et al., 2015) but several species remain poorly collected. A recent collection from northern Zambia stands out in its tall stature, sometimes exceeding 1.3 m, and multibranched spike bearing numerous relatively small, dark purple flowers. It cannot be accommodated in any known species and we conclude that it represents a new species that we describe here as Z. atropurpurea. 2. Materials and methods All relevant type material was examined, as well as all herbarium material from BOL, MO, NBG, NDO, NU, PRE, K, SAM and UZL (acronyms after Thiers, 2017). The new species was studied in the field. 3. Taxonomy 3.1. Key to species of Zygotritonia ⁎ Corresponding author at: Missouri Botanical Garden, P.O. Box 299, St. Louis, MO 63166, USA. E-mail address: peter.goldblatt@mobot.org (P. Goldblatt). https://doi.org/10.1016/j.sajb.2019.04.016 0254-6299/© 2019 SAAB. Published by Elsevier B.V. All rights reserved. 1a Flowering stem either bearing sheathing leaves only or leaves with blades shorter than the sheaths (foliage leaves produced after flowering from separate shoots in some species): 21 P. Goldblatt et al. / South African Journal of Botany 124 (2019) 20–22 3a Leaf blade ribbed, mostly 1–3 mm wide; floral bracts dry, 2–3 mm long; upper tepal 6–8 mm long ... Z. praecox Stapf. 3b Leaf blade pleated and ribbed, 3–5 mm wide; floral bracts green below, ± 3 mm long; upper tepal ± 4.5 mm long … Z. benishangula Goldblatt & Sebsebe. 1b Flowering stem bearing foliage leaves with blades at least as long as sheaths or much longer: 4a Foliage leaf blade ± terete, b2 mm at widest diameter; plants up to 200 mm tall ... Z. teretifolia Goldblatt & J.C.Manning. 4b Foliage leaf blade lightly pleated with blade at least 3 mm wide; plants 150 to over 1000 mm tall: 5a Uppermost cataphyll straight, sheathing throughout (not spreading to revolute and with straight margins); floral bracts dark green, smooth or rugose, not regularly minutely papillate ... Z. bongensis Mildbr. 5b Uppermost cataphyll with spreading to revolute apex; floral bracts pale green to dry straw-coloured: 6a Plants to ±450 mm tall; uppermost cataphyll with straight margins; spike simple or few-branched; floral bracts minutely papillate (using 10 × magnification); dorsal tepal 9–12 mm long ... Z. nyassana Mildbr. 6b Plants mostly 1.0–1.3 m tall; uppermost cataphyll with undulate margins; spike several-branched; floral bracts smooth (using 10× magnification); dorsal tepal ±7 mm long ... Z. atropurpurea Goldblatt & J.C. Manning. 3.2. Zygotritonia atropurpurea Goldblatt & J.C.Manning, sp. nov. Fig. 1. Fruiting stem of Zygotritonia atropurpurea, showing multiple branches of flowering stem and developing capsules (McCleland & N. Wightman s.n.). Fig. 2. Flowers of Zygotritonia atropurpurea (McCleland & N. Wightman s.n.). 2a Plants usually N300 mm and up to 500 mm tall; flowering stem bearing 2 or 3 sheathing leaves without free blades; sometimes imbricate ... Z. hysterantha Goldblatt. 2b Plants rarely exceeding 250 mm; flowering stem bearing 1 or 2 leaves, these sheathing stem for most of their length but with free blade shorter than sheath; always imbricate: Type: Zambia, Mporokoso District, Northern Province, near the Kalungwishi River in Brachystegia woodland, 1172 alt., May 2017, W. McCleland & N. Wightman s.n. (K, holo.!; NDO, NU!, UZL, iso.). Plants mostly ±1.0 m but up to 1.3 m high. Corm globose, ±18 mm diam.; tunics fibrous, light brown. Cataphyll evidently solitary, 70–80 mm long, dry-membranous, sheathing below, with tapering, recurved apex and undulate margins. Stem several branched (up to 8) in upper fifth, bearing 6 or 7 overlapping sheathing leaves. Foliage leaf solitary, inserted near base, reaching to about base of spike, lanceolate, ±15 mm at widest, shallowly pleated, margins not obviously thickened, tapering below to narrow, thickened base ±3 mm diam. Inflorescence several branched (up to 8), lower 2 or 3 with secondary branches, each branch a several-flowered spike; bracts green below, dry apically, subequal, 3–4 mm long. Flowers predominantly dark maroon-purple, lower five tepals with pale whitish transverse band above base and paler purple distally, anthers ± red-black; perianth tube 3–4 mm long, ± cylindric below, widening gradually in upper half; tepals unequal, dorsal ± linear-spathulate, arcuate in bud but directed forward horizontally after anthesis, ± 7 × 1.5–2.0 mm, upper lateral tepals recurving, lower three tepals united for ±1 mm, directed downward, pale purple distal to white band, ±3.0 × 1.5 mm, abruptly expanded and spooned in distal 2 mm. Stamens unilateral, arcuate, almost reaching apex of dorsal tepal; filaments ± 5 mm long; anthers ± 1.0–1.5 mm long, linear, rounded at apex, parallel, dark purple. Ovary subglobose, ± 1.5 mm long; style arching adaxial to stamens, reaching to lower third of anthers, curving downward distally below anthers when apparently receptive, evidently undivided at apex. Capsules ± 3 mm long, broadly 3-lobed, locules evidently 2-seeded or 1 by reduction. Seeds probably 3 mm diam. [only immature seeds seen]. Flowering time: March–April, possibly also in February. (Fig. 1). (See Fig. 2.) Table 1 Comparison of significant morphological characters of Zygotritonia atropurpurea, Z. bongensis and Z. nyassana. Species No. sheathing leaves No. foliage leaves Plant height Flower colour Dorsal tepal length Lower tepal length Filament length Z. atropurpurea Z. nyassana Z. bongensis 6 or 7 2 (or 3) 2 largely sheathing 1 2 Usually 2 N100 cm or more 20–45 cm Mostly 40–65 cm Dark purple Pink or mauve to orange Mauve or orange ±7 mm 9–12 mm ±12 mm ± 3 mm 5–6 mm 7–8 mm 4 mm 9–10 mm 8–10 mm 22 P. Goldblatt et al. / South African Journal of Botany 124 (2019) 20–22 Distribution: known only from Mporokoso District, Northern Province, Zambia, on the eastern side of the Kalungwishi River slightly downstream of Lumangwe Falls in closed semi-deciduous woodland dominated by several Brachystegia species and Julbernardia paniculata. Plants were growing on a gentle slope above the river in a welldeveloped grassy understory on sandy-gravelly soil. Diagnosis: remarkable for its solitary foliage leaf tapering in the lower half to a subterete base, and its multibranched stems, each branch a many-flowered spike, Zygotritonia atropurpurea also has unusually small flowers for the genus, dark purple in colour, with a dorsal tepal ±7 × 1.5–2.0 mm and lower three tepals ± 3.0 × 1.5 mm. Consistent with the small flowers, the filaments are 4 mm long. The tall stems, up to 1.3 m high are unique in the genus (Table 1). The uppermost cataphyll is recurved in the upper part and the margins are undulate. Discovered in 2017 in Northern Zambia by Warren McCleland and Nicholas Wightman, Zygotritonia atropurpurea is so distinctive a species that it is difficult to assess its relationships in this small genus. The relatively broad foliage leaf, present at flowering time, links it to the West African Z. bongensis and the south tropical African Z. nyassana, both of which have well developed, softly pleated foliage leaves (Goldblatt, 1989). Zygotritonia bongensis, a plant of moderate height, up to 65 cm, has larger, orange or mauve flowers, and the uppermost cataphyll sheathes the lower part of the next leaf. Zygotritonia nyassana, also a shorter plant, up to 45 cm, has pale pink, mauve to orange and white flowers, also significantly larger than those of Z. atropurpurea (Table 1) but the tapering apex of the upper cataphyll is recurved and minutely papillate, recalling in part the recurved cataphyll apex of Z. atropurpurea but the surface of that species lacks papillae and the more or less dry margins are undulate. Acknowledgments We thank Benny Bytebier, University of KwaZulu-Natal for making available facilities at the Bews Herbarium to examine collections of Zygotritonia atropurpurea there. References Goldblatt, P., 1989. Revision of the tropical African genus Zygotritonia (Iridaceae). Bulletin du Museum d'Histoire Naturelle, 4 sér., sect. B, Adansonia. vol. 11, pp. 199–212. Goldblatt, P., Manning, J.C., 2008. The Iris family: natural history and classification. Timber Press, Portland, OR. Goldblatt, P., Manning, J.C., Demissew, Sebsebe, 2015. Zygotritonia Mildbr. (Iridaceae: Crocoideae), new species from eastern tropical Africa and notes on the morphology of the genus. S. Afr. J. Bot. 96, 37–41. https://doi.org/10.1016/j.sajb.2014.11.006. Goldblatt, P., Manning, J.C., Demissew, Sebsebe, Malakasi, P., Forest, F., 2016. Relationships of the sub-Saharan African genus Zygotritonia Mildbr. (Iridaceae: Crocoideae) inferred from molecular analysis. S. Afr. J. Bot. 105, 5–7. Mildbraed, J., 1923. Iridaceae Africanae. Botanische Jahrbucher für Systematik 58, 230–233. Thiers, B., 2017. Index Herbariorum: A Global Directory of Public Herbaria and Associated Staff. New York Botanical Garden's Virtual Herbarium http://sweetgum.nybg.org/ih/, Accessed date: 20 December 2018.