Aspidoglossum albocoronatum Bester & Nicholas, 2016

Bester, Stoffel P. & Nicholas, Ashley, 2016, Aspidoglossum albocoronatum (Apocynaceae, Asclepiadoideae), a new species with a remarkable petaloid corona from the northern provinces of South Africa, Phytotaxa 282 (3), pp. 186-196 : 188-195

Aspidoglossum albocoronatum Bester & Nicholas , spec. nov. ( Figs. 1–5 )

Distinguished from other species of Aspidoglossum by the conspicuously elaborate and apically fimbriate corona (leading to the flowers resembling a carnation) and terminal inflorescence.Allied to Aspidoglossum dissimile and with distant connections to Schizoglossum and Miraglossum , but differing from these genera in having terminal and sessile inflorescences (in Schizoglossum pedunculated and in Miraglossum axillary inflorescences).

Type:— SOUTH AFRICA, Limpopo Province, 2430 (Pilgrim’s Rest): southern Leolo Mountains below Thamagoshi Peak near the village of Thamagoshi (–CA) on norite-derived loamy soils, north–eastern aspect, 1758 m, 20 January 2005, S.P. Bester 5591 (holotype, PRE!; isotypes, E!, J!, K!, MO!, NH!, PRU!) .

Perennial geophytic herb with milky latex. Underground organ fleshy, rounded and turnip-shaped to elongated napiform tuber, 30–110 × 4–23 mm, neck cylindrical, 5–66 mm long, rarely branched, pale cream-coloured with fibrous outer layer. Stem erect, rarely branched, if branched then not from base, sparsely to densely foliate, villous, 70–360(–530) mm tall. Leaves opposite to sub–opposite, decussate, sometimes three–whorled becoming alternate towards the apex, usually 6–11 pairs, simple, erect to spreading erect; lamina narrowly oblong to lanceolate, 12–70 × 2–12 mm, basal 1 or 2 pairs of leaves shorter than the rest, then becoming gradually shorter toward the apex, hirsute, hairs sparsely distributed, base obtuse to somewhat truncate or asymmetrical to oblique, apex acute to attenuate, margins revolute, paler below with fewer hairs, midvein prominent, smooth to scabrid or hirsute, slightly incurved adaxial, bulged out and prominent abaxially, paler in contrast to abaxial surface; petiole 1–4 mm long, sparsely pubescent. Inflorescence mostly in solitary and terminal sessile umbels 28–45 mm in diameter, rarely a second umbel developing from the basal inflorescence then with a short peduncle 2–4 mm long; rarely in particularly robust plants the stems may be two or three branched then umbels also terminal and sessile on branches; bracts filamentous–linear, (4–) 5–8 (–10) × 0.24–1.5 mm, scabrid dorsally, glabrous ventrally. Flowers 3–16 per umbel, 4–5 mm in diameter; pedicels, (3–) 6–15 (–18) mm long, puberulous, recurving after pollination, puberulous; calyx erect to spreading-erect, free, only fused at the base, lobes ovate to lanceolate, acute, usually half as long as the corolla, 4–8 × 1–1.5 mm, apex acute, ventral surface glabrous, dorsal surface with scabrid hairs at base, dark olive–green to greyish; corolla divided to the base, spreading erect to recurved at anthesis, soon rolled up or coiled after anthesis; lobes ovate to lanceolate, 5–8 × 2.5–4 mm, apex acute, ventrally glabrous and dorsally sparsely scabrid towards the base and middle of the lobe; outside maroon or purplish to greyish green and rarely striated, paler greenish inside; staminal corona arising at the base of the gynostegial column; lobes free, erect, dorsiventrally flattened; lobe 5–11 × 4–8 mm with two divided appendages on ventral face, apically randomly fimbriate to serrated; lower ventral appendage ovoid, ovate-lanceolate, oblongligulate, 3–4 × 1.4–2.2 mm; upper ventral appendage 0.49–1.44 × 0.10–0.34 mm with globose papillae near base, obtuse with two keels on the lateral sides, apex variously fimbriate; lobes much longer than the staminal column, pure white or cream with pink–maroon tinge on rare occasions; staminal column cylindrical or barrel-shaped, 1.8–2.3 × 1.6–1.9 mm, white; stamens with anther-wings triangular, broadest in the base, 0.8–1.2 × 0.3 mm wide extending 0.2– 0.3 mm outward; anther appendages ovate, broadly ovate, obtuse with tips erect-inflexed over the style-apex, apex obtuse to acute; style-apex rounded to rounded-conical and concave at apex, exceeding the anthers, white; pollinaria with pollinia oblong and slightly curved, 0.47–0.53 × 0.15–0.16 mm; caudicle horizontal orientated in anther–sac, 0.12–0.22 × 0.02–0.08 mm, widely diverging, affixed at the base to the corpusculum and terminally to the pollinium, flat and ribbon-like at attachment with corpusculum becoming broad and flat at attachment with pollinia; corpusculum oblong, elongated-ovoid to ovoid, sub-acute, 0.23–0.30 mm long. Fruit fusiform, 70–76 × ca. 12 mm, broadest in the middle, outer surface echinate with soft prickles to 3 mm long, green; seed (immature?) 1.5 × 2 mm with coma 15–18 mm long, white; fruiting pedicel recurved.

Etymology: — The specific epithet is a conjunction of alba (meaning white) and coronatum (meaning crown), referring to the five white coronal lobes which are very distinctive in appearance and form a structure resembling a crown ( Fig. 1D ).

Distribution and habitat:— South African endemic collected in Limpopo and Mpumalanga Provinces ( Fig. 6 ). Growing at an altitude between 1600–1900 m on hilltops and mountain slopes in well–drained loamy to humic, mainly norite–derived soils in rocky grassland mixed with scrub. This species grows in an area that fall within the Sekhukhuneland centre of Endemism ( Siebert et al. 2001, 2002), which has revealed numerous new species ( Siebert et al. 2010).

Phenology:— On a visit to Thamagoshi on 2 December 2004 three plants were found.At that stage the plants were already fully grown. The umbels were visible with flower buds of 1–2 mm long. Also at that stage the bracts formed an almost cage-like structure around the umbel. Development seems to be rather slow and 11 / 2 months later the plants were in full flower. Based on the specimens examined the flowering time stretches from November to April. Based on our observations we speculate that there is some kind of synchronising mechanism for flowering leading to an almost simultaneous flowering in a population. During a visit to Thamagoshi on 20 January 2005 less than 1% of plants showed some development of fruit, the rest being in full flower. At this time no plants with developed fruit or any plants in bud were encountered. The corolla was totally recurved exposing the large elaborate corona during anthesis. Soon after anthesis the corolla becomes rolled-up longitudinally (coiled) in most plants. No possible pollinators were observed on plants (during daytime), nor did the plants had any distinguishable scent during day light hours. It would be interesting to test if the pure white corona might indicate a crepuscular pollination syndrome adapted to moth pollination. After the flowers are pollinated or as the flowers die the corolla seem to unwind slowly becoming erect. At this stage the pedicel also starts to recurve and bend downwards. Thus far fruits were only collected in April. As the winter conditions where these plants grow are harsh (including occasional snow-falls) and veld fires are common in spring, it is postulated that the seeds are distributed at the end of the growing season and stay dormant until springtime. During these unfavourable times the above ground stems die back and the plants survive underground.

Conservation status:— As a vast areas in this region remain unexplored at present this taxon should probably be listed as data deficient (DD) ( IUCN 2001, Victor 2006). Mrs. M. Lehman indicated that she has visited the Thamagoshi area a few times and found Aspidoglossum albocoronatum to be rather common. The first author agrees, but to him it seemed to be rather occasionally scattered over vast areas and restricted to grasslands. There are two subpopulations scattered over an area of about 710 km 2, where the species is quite common but threatened by various mining activities. However, since there are more than 10 locations (23), the criteria for a category of threat are not met. Because this species may be declining (at least one location is known to be destroyed), it is appropriate to assess A. albocoronatum as Near Threatened (NT) according to the IUCN (2001) criteria.

Ethnobotanic Uses: — Aspidoglossum albocoronatum does not seem to be utilized extensively. However, Mr. Jim Mariri, a local inhabitant at Leolo, said: ‘the tuber is edible, the outer fibrous layer is peeled off and the inner parts are given to young children to keep them busy when they are hungry’. According to him it is not used medicinally. He also mentioned that the regional name for the plant is ‘ Segwete’. The vernacular name ‘ Segwete’ is, however, used for various species in the Asclepiadoideae that are used medicinally (Mr. Tšhiane, pers. comm.). Segwete is a generic term in Setswana/siSwati for carrot. No signs of grazing were observed.

Notes: —Morphologically this new species is allied to A. dissimile in that the apical portion of the basal lobe of the staminal corona is similarly fimbriate or crispate with the distinction of the inner appendage that is never “split”. The inflorescences in A. dissimile are also not strictly apical but axillary and indeterminate (compared to apical and determinate in A. albocoronatum ). There are a number differences between our new species and the circumscription of Aspidoglossum sensu Kupicha (1984) that are indicated in Tab. 1. Further, molecular work place A. albocoronatum in the well-supported Aspidoglossum-clade (Bester et al., unpublished).

Our new species further superficially resembles members of the tropical genus Margaretta because it has petaloid corona lobes but preliminary phylogenetical work (Bester et al., unpublished) place A. albocoronatum and Margaretta spp. in different and well-defined clades and the former in the well-supported Aspidoglossum -clade. The basic structure of the corona is a dorso–ventral flattened lobe splitting into two primary apical portions with two teeth on the ventral face. The upper tooth is inserted at the apical split with the lower tooth closer to the base. The upper tooth is usually unbranched and shows less variation than the lower tooth. The lower tooth ranges in length, number of branches and width. Within a single flower two adjacent lobes show a range of variation; hence the generic name ( Fig. 2 ). This remarkably high level of variation was observed between flowers from the same umbel, populations and localities ( Fig. 4 ). Margaretta is the only other genus in the subtribe Asclepiadinae that have petaloid corona lobes. Our new species is further distinguished from the species of Margaretta which have pollinia ovoid to pyriform in shape; the absence of a germination zone on the pollinia; the translator arms that are flat, ribbon-like and ridged; corona lobes that has a claw; and a fruiting peduncle that is straight.

Colour variation has been reported on some collections indicating that the flowers are white to yellow to purple and cream. The petals are maroon or purplish to greyish green on the outside and much paler on the inside. Because of the prominence of the corona it is assumed that the reference of some of the labels indicating flower colour actually referred to the colour of the corona which may vary from pure white to cream sometimes with pinkish-maroon tinges.

Additional material examined:— SOUTH AFRICA. Limpopo Province: Lulu Mountains, Het Fort farm, 7 January 1939, W.G. Barnard & A.O.D. Mogg 1038 ( PRE!) ; Leolo Mountains , 20 January 2005, S.P. Bester 5546 (MO!, PRE!, UDW!), 5550 (NU!, PRE!, PRU!, SRGH!, Z!), 5552 ( PRE!, BNRH!), 5562 ( LYD!, PRE!), 5592 ( MO!, PRE!), 5593 ( PRE!, UNIN!) ; Lebowa, Leolo Mountains, ca. 1.6 km direct S of Thamagoshi Peak. ± 4.2 km ENE from Sekhukune village and 30 km WSW from Burgersfort , 1 November 2010, S.P. Bester 9819 (PRE). Sekhukhuneland, footslopes of Tama Kgoshi Peak ( Leolo Mountains ), Soupiana 325KT farm, 5 February 2013, S.P. Bester 11482 ( PRE!, LYD!), 11483 ( PRE!). Sekhukhune, Leolo Mountain , 5 February 2011, S. Kremer-Köhne 102 ( PRE!) ; Sekhukhuneland, Leolo (Lulu) Mountains , 20 January 2005, M.K. Maserumule 367 (B!, JBG!, PRE!) ; Leolo Mountains, Thamagoshi Village next to main road, 20 January 2005, A. Masombuka 350 (J!, PRE!, UDW!, UNIN!) ; Lulu [Leolo] Mountains, Patswana Thamagoshi , 20 January 2005, N. Swelankomo 189 (LYD!, NBG!, PRE!) ; Salpeterkrans , 22 January 1997, J.V. van Greuning & al. 672 ( PRU!) ; Leolo Mountains, ca 200 m E of crest of pass, 8 m south of road, 14 March 2007, P.J.D. Winter 7135 (PRE! with follicle only). Mpumalanga Province: Roossenekal district, Uitkyk & Naaupoort farms in Tonteldoos area , 11 January 1997, K. Balkwill 9610 (J!, K) ; Roossenekal, 4.5 km on Lydenburg road from Mapoch Cave turn-off on left, take gravel road 3 km, 28 April 1999, S.J. Siebert 830 (PRU! fruit remains) ; Dullstroom District ; Middelkraal farm, 24 January 1994, R. Smit 2669 ( PRU!) ; Belfast District, Doornkop farm, January 1912, J. Thode 2644 ( NBG!) ; Roossenekal, Eagle Quarries , 1 April 2000, A.E. van Wyk & S.J. Siebert 1426 ( PRU!) ; Roossenekal District, Tonteldoos area, Newby farm, 20 January 2001, P.J.D. Winter 4630 ( PRE!, UNIN!) .

Figures

FIGURE 1. Aspidoglossum albocoronatum from Leolo Mountains, Sekhukhuneland, South Africa.A, flowers close-up showing elaborate corona lobes (white) and diminutive corolla rolled and twisted (maroon-brown). B, F, G, apical and sessile inflorescence in various views. C, leaves opposite to sub-opposite along stem (becoming verticillate towards apex—not shown here). D, E, leaves showing adaxial (left) and abaxial (right) sides with indumentum and prominent main vein. Scale bars: 10 mm. Photos: S.P. Bester.

FIGURE 2. Aspidoglossum albocoronatum:A, apical portion of plant; B, basal portion of plant with neck and tuber; C, pollinarium frontal view; D, pollinarium side view; E, gynostegial column viewed from side; F, semi-mature fruit; G, base of fruit showing contorted pedicel; H, transverse section through leaf showing revolute margins.A, B, E, H: Bester 5591 (PRE); C, D: Bester 5546; F, Winter 7135 (PRE); G, Siebert 830 (PRU). Scale bars: A, B, F (at A): 20 mm; C, D (at C): 0.24 mm; E, 1.2 mm; G, 5 mm; H, 8 mm.Artist: G. Condy.

FIGURE 3. Aspidoglossum albocoronatum: A–C, flower: A, viewed from side, front calyx and corolla removed; B, viewed from above; C, viewed from side, front calyx, corolla and corona-lobe removed. D & E: corolla: D, ventral side; E, dorsal side. F & G, calyx: F, ventral side; G, dorsal side. H–J: corona-lobe; H, side view with ventral appendages (“horns”) to the left projecting over gynostegial column; I, ventral view; J, dorsal view. A–J: Bester 5591 (PRE). Scale bars: A–C (at C), 30 mm; D–G (at D), 2.5 mm; H–J (at H), 1.25 mm. Artist: G. Condy.

FIGURE 4. Variation in morphological expression of the staminal corona-lobes of Aspidoglossum albocoronatum. A–E: dorsal view of the five corona-lobes from a single flower showing the variation in expression of the main lobe to the back and the ventral appendage, Bester 5591. F–K, each pair showing one corona-lobe from different flowers (different collections), F 1 –K 1, ventral side; F 2 –K 2, dorsal side. F, Balkwill & Balkwill 9610; G, Maserumule 367; H, Swelankomo 189; I, Winter 4630; J, Bester 5546; K, Bester 5591. Scale bar: 0.6 mm. Artist: G. Condy.

FIGURE 5. Aspidoglossum albocoronatum. Scan of the holotype, Bester 5591 (PRE! with tuber).

FIGURE 6. Known distribution of Aspidoglossum albocoronatum (z). Map created in ArcGIS 10.1.