Bulbine decastroi Gideon F.Sm., 2023

Smith, Gideon F., Grobler, Retief & Hankey, Andrew, 2023, Bulbine decastroi (Asphodelaceae subfam. Asphodeloideae), a new peatland species with grass tuft-like rosettes from Mpumalanga, South Africa, Phytotaxa 587 (1), pp. 59-65 : 60-64

Bulbine decastroi Gideon F.Sm. , sp. nov.

Type: SOUTH AFRICA. Mpumalanga province. North-central region of the province . Steenkampsberge . 14 October 2022, G.F. Smith 1202 (holotype PRU) .

Diagnosis:— Bulbine decastroi differs from B. capitata in being somewhat smaller and daintier in most vegetative respects. The glaucous leaves of B. decastroi are relatively short and narrow (120–180 × 1.0– 1.5 mm), while those of B. capitata are light to mid-green and usually more robust (400 × 3 mm). Bulbine decastroi has contractile roots, an adaptation to its peatland habitat, while the roots of B. capitata are not contractile. Bulbine decastroi often grows in dense clusters of up to 40 plants, while up to six plants of B. capitata can be clustered together, but they are usually well spaced. The inflorescences of B. decastroi are fewer-flowered than those of B. capitata , and the pedicels of B. decastroi are generally shorter than those of B. capitata .

Description:—Perennial, acaulescent, small, rosulate leaf succulent up to 0.18 m tall in vegetative phase, at first solitary, with age dividing basally to form clusters with up to 40 rosettes, each with short pseudo-stem (5–) 10–12 mm long. Pseudo-stem generally devoid of persistent, basal leaf material. Roots wiry to somewhat succulent, up to 1.5 mm in diameter, contractile, white to pinkish yellow. Leaves 120–180 × 1.0– 1.5 mm, distinctly graminoid, soft-textured, flexuous, numerous, erect to erectly spreading, old leaves eventually shed; blade mid- to dark green with a glaucous sheen, senescing pinkish brown, narrowly linear, attenuate, at 15 mm from base broadening gradually downwards to width of ± 10 mm, gradually and narrowly tapering towards apex; adaxial surface flat to concave, longitudinally grooved; abaxial surface convex, lacking striations; margins entire; apex acute, hardly drying from tip. Inflorescence a cylindrical raceme, appearing subcapitate when few flowers open simultaneously, usually 1 arising from a rosette, few- to subdensely-flowered (8–20), 0.1–0.4 m tall, ascending to slightly spreading, elongating somewhat as flowering proceeds upwards; peduncle 3–4 mm in diameter, round in cross-section, slightly tapering upwards, glabrous, not sterile bracteate, drying pinkish brown. Flowers rather densely borne in upper ⅓ to 1 / 5 of inflorescence, 13–15 mm in diameter, 5–7 mm apart, 3–6(–8) open simultaneously, diurnal, open from ± 08:00–17:00, closing in inclement weather; floral bracts deltoid-acuminate, 5–6 mm long, 2–3 mm broad at base, membranous, clasping peduncle and higher up the pedicel, light brown with dark brown central vein, margins lacerate, base auriculate, auricles creamy white; pedicels slender, 12–16 mm long in bud and at early anthesis, sometimes elongating to 25–40 mm long in fruit, erectly spreading in both flower and fruit, persistent when dry, rarely slightly recurved when barren; perianth a stellate perigone; tepals in two whorls, bright, glistening yellow, margins somewhat rolled under, 1-nerved, vein light green, raised below; outer tepals elliptic, 6–8 × 3.0– 3.5 mm, apices blunt-tipped, sometimes slightly notched, variously flat to up- or down-curved in apical ½; inner tepals ovate to round, 5–7 × 3.0– 3.5 mm, apices blunt-tipped. Stamens distinctly spreading at 30° from vertical, up to 2–3 mm long; filaments yellow, slender, hairy in lower ½; anthers light brown, oblong, dorsifixed. Ovary globose, 1.0– 1.5 mm in diameter; style erect, terete, up to 2 mm long; stigma apical, minutely capitate, whitish yellow. Fruit a globose, loculicidal capsule, up to 4.5 mm in diameter, light green, at maturity, at first enveloped in dark brownish black remains of perigone. Seed 0.75(–1.00) × 1.0(–1.5) mm, black, ± D-shaped, angled, few per capsule. Chromosome number: unknown.

Flowering time:— Bulbine decastroi flowers from spring to mid-summer (September to December) in the southern hemisphere.

Natural geographical distribution range:— Bulbine decastroi is currently only known from three localities that are in close proximity in the Steenkampsberge in north-central Mpumalanga in South Africa.

Except for the most general, no locality data from specimens or field observations are given. This deviation from widely followed taxonomic practice is justified by the fact that poaching of succulent plants from the wild in South Africa is a severe and escalating problem, and it was decided not to provide any information regarding the exact whereabouts of this new species that could cause known populations to be targeted for destructive collecting ( Smith et al. 2023).

Habitat:— Bulbine decastroi is a habitat specialist that occurs on true peat substrates with a dead soil organic matter content of over 30% (dry mass) ( Joosten & Clark 2002, Grobler 2022) in high-altitude mire peatlands in valleybottom and seep settings ( Ollis et al. 2013), and is absent from hydromorphic mineral soils situated directly adjacent to these mires. The three known localities where B. decastroi occurs on the quarzitic plateau of the Steenkampsberge are at elevations ranging from ca. 2100 to 2245 metres above sea level. The mire wetlands that comprise the habitat of B. decastroi are embedded within grassland vegetation representative of the Steenkampsberg Montane Grassland vegetation type ( Dayaram et al. 2017).

Bulbine decastroi is an obligate hygrophyte (sensu Retief & Herman 1997) that occurs in near-pristine mires vegetated by dense herbaceous plant communities comprised entirely of hygrophytes.

Conservation status:— Bulbine decastroi is currently known from three localities, each representing a distinct subpopulation, within a very small Extent of Occurrence (sensu IUCN 2022) of ca. 20 km 2. All known localities are located in South Africa’s Mpumalanga province within two formally protected areas and there are currently no known significant threats to this species or its habitat. It is therefore considered to be unlikely that B. decastroi currently meets the IUCN thresholds for categorisation as threatened (CR [Critically Endangered], EN [Endangered], or VU [Vulnerable]) or Near Threatened (NT) ( IUCN 2012). However, B. decastroi is regarded as ‘Rare’ in accordance with the South African conservation status categories used by Raimondo et al. (2009).

Eponymy:— Bulbine decastroi is named for Antonio (‘Tony’) D’Azevêdo Pinto de Castro (Lourenço Marques [present-day Maputo], Mozambique, 17 January 1970 –) ( Fig. 1F ). He matriculated from King Edward VII High School in Johannesburg in 1987, after which he attended the Rand Afrikaans University (currently the University of Johannesburg), graduating with a B.Sc. (Hons) degree in Botany in 1994. In 1997 Tony entered his current occupation as a professional consultant in the fields of botany and ecology, and in 1999 he founded De Castro & Brits c.c. an ecological consulting firm of which he is at present the Managing Member. He is a registered member of the South African Council for Natural Scientific Professions and conducts specialist work in, inter alia, terrestrial, wetland, and riparian ecosystems of the Savanna and Grassland Biomes of southern Africa. Tony has worked in 13 African countries, and as part of his field surveys has authored several scientific papers and over 570 specialist reports pertaining to biodiversity management, impact assessment, and the sustainable utilisation of natural resources.

Figures

FIGURE 1. Bulbine decastroi. A. In its natural peatland habitat. The peatland burned a few months before the photograph was taken. Note the high water table in the bottom right of the image. B. This section of the peatland did not burn. The vegetation is very dense. C. Contractile roots. D. A dense cluster of 40 rosettes. Note the glaucous sheen to the leaves. E. Close-up of racemes and flowers. F. Tony de Castro (1970–) after whom B. decastroi is named. Bulbine decastroi grows in the foreground. All photographs: Gideon F. Smith.