Sansevieria rukwana M.Burkart, Piniely, Sikawa & Yinger, 2025

Burkart, Michael, Kavula, Kened Alfred, Constantine, Immaculate Kileo, Mollel, Neduvoto Piniel, Piniely, Luciana Naftal, Sikawa, Robert Augustino & Yinger, Barry R., 2025, Sansevieria bangalalana sp. nov. (Asparagales, Asparagaceae), close to extinction in the wild, and five other narrowly endemic and threatened species of Sansevieria from Tanzania previously unknown to science, European Journal of Taxonomy 1026, pp. 65-106 : 98-102

Sansevieria rukwana M.Burkart, Piniely, Sikawa & Yinger sp. nov.

urn:lsid:ipni.org:names:77370782-1

Figs 1, 25–27, Table 3

Diagnosis

Sansevieria rukwana sp. nov. seems to be similar to S. kirkii , but the leaves in S. rukwana are shorter and wider, lacking a pseudo-petiole as well as a strong ridge on the abaxial side but showing a silky gloss on both sides, characters different from that in S. kirkii . Also, the rhizome inner cortex is orange instead of brown as in S. kirkii , the peduncle, the bracts of the partial inflorescences and the styles all are shorter, and the flower odour is different in S. rukwana . The capitate but slightly elongate inflorescence (or its remnants, Fig. 25B) is typical for S. rukwana and indicates that it belongs to the subgenus Capitulatus .

Etymology

Sansevieria rukwana sp. nov. is named for Rukwa Region where this species is found.

Type material

TANZANIA • Rukwa Region; 1039 m a.s.l.; 19 Oct. 2021; B. Yinger & R.A. Sikawa YS 0925; holotype: NHT [ 000001157 ] .

Living specimens ex typo cultivated at TSF and POTSD.

Description

Acaulescent herb, rhizomatous, vegetative height to 1600 mm ††, to 620 mm #, 2–3 leaves per shoot. Rhizome belowground, ca 30 mm in diameter, forming short runners, colour of inner cortex dark reddish orange 172B. Leaves ( Figs 25A, 26) pointing to all directions, upright to spreading to almost horizontal, stiff but twistable, to 1600 mm long, to 110 mm wide, oblanceolate, slightly twisted, petiole missing, leaf base ca 21 mm wide, central lamina thickness 6 mm, basal thickness 16 mm, flat but u-shaped in cross-section, without a pronounced ridge on the abaxial side, surface very smooth on the adaxial side, smooth on the abaxial side, both sides with silk gloss†† and a heavy, conspicuous glaucous bloom; colour pattern distinct on the adaxial side, cloudy, without dark longitudinal lines, pattern less prominent on the abaxial side, forming transverse bands, lighter and darker parts 50: 50, with up to 9 dark longitudinal lines, colour pattern in older leaves weaker than in young ones; margin sinuate, red-brown and whitish; leaf tip leathery, to 29 mm long. Inflorescence ( Figs 26–27) terminal on fully leaved shoots, capitate, 223 mm long; peduncle 163 mm long, 20 mm thick, patterned with small dots and lines, dark greyish reddish brown 200A, with 4 bracts; peduncle bracts 46–114 mm long, dry at anthesis, light olive 152B; flower-bearing part of axis 60 mm long, flowering head 135 mm in diameter excluding anthers and styles, dense, 2–3 flowers per partial inflorescence, less in the uppermost part, 201 flowers counted on one head; bracts of partial inflorescences 17–23 mm long, 7–12 mm wide, herbaceous (not dry), lanceolate-elliptic, with up to 5 nerves, without extrafloral nectaries; pedicels inarticulate, 10 mm long, light olive 152A, wilted flowers not dropping. Flowers with flowery but astringent odour, greenish white 155C outside, wilted greyish yellow green 148C, with some pinkish striation most prominent on young buds ( Fig. 27A), 133 mm long overall; tube 100 mm long; lobes 33 mm long, inner lobes 4 mm wide, outer lobes 3 mm wide, strongly to intermediately curled back at anthesis; filaments greenish white 155C, 31 mm long, thread-like; anthers 4 mm long, strong yellow green 144C; style white, straight, 123 mm long above ovary, 45 mm exsert from tube mouth; stigma 1.5 mm wide, white; ovary ovoid with truncate apex, strong yellow green 144C; infructescence capitate but slightly elongate#. Fruits and seeds unknown.

Ecology and distribution

This species was collected only once in an area of steep wooded ravines and rocky slopes above streams within the Lake Rukwa drainage area. Although much of this area is still intact forest, the location of this collection was in a partially disturbed area where tree cover was mostly removed.

Taxonomic remarks

Sansevieria rukwana sp. nov. is superficially similar to S. kirkii . An overview of the differences is given in the diagnosis above and also in Table 3 . Sansevieria kirkii is relatively widespread in Indian Ocean coastal lowlands, far away from the small and restricted W Tanzanian realm of S. rukwana . Although many records exist from a wide geographical scene that claim to be S. kirkii , they lack true confirmation of their taxonomic identity. Moreover, the proper taxonomy of S. kirkii var. kirkii and var. pulchra N.E.Br. is still unresolved ( Newton 2020; MB and U. Scharf, pers. obs.).

Tentative threat assessment

Endangered: EN D.

We found what we are certain is this species only once in a mostly undisturbed area. The colony that we saw is about 150 plants. This area is very difficult to navigate and there are vast areas of similar topography there. We saw a number of other plants of Sansevieria there, but nothing with the distinctive infructescence remnant of S. rukwana sp. nov. ( Fig. 25B). This area was under no obvious immediate threat because of its steep rocky topography, but recently, a mine for iron ore has been proposed very close to the type location; in two days of surveying this area, no other colonies were seen. Based strictly on what we have observed, its threat status is EN (criterion D, <250 mature individuals), although the situation might change drastically if mining begins.