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| Stylochaeton sekhukhuniense Struwig, S.J.Siebert & A.E.van Wyk, in Struwig, Le Roux, Siebert et van Wyk. 2023. Photographs: A.E. van Wyk (A, C & D) and S.J. Siebert (B). |
Abstract
We are describing here Stylochaeton glaucophyllum and S. sekhukhuniense, two new species from northeastern South Africa. Both species have a restricted distribution and are endemic to the Sekhukhuneland Centre of Plant Endemism, Limpopo and Mpumalanga Provinces, South Africa. The new species occur sympatrically with S. natalense, but never with one another. Stylochaeton glaucophyllum prefers norite and pyroxenite hills and mountains, whereas S. sekhukhuniense is associated with similar rock types in low-lying rocky areas. Both new species have the base of the spadix and infructescence partly below-ground and are mainly associated with open savannah. Stylochaeton glaucophyllum can be distinguished from S. sekhukhuniense in having greenish blue leaves with linear lobes while S. sekhukhuniense has green leaves with elliptic lobes. The leaves of S. glaucophyllum are longer (112–332 mm) than those of S. sekhukhuniense (44–180 mm). The petiolar sheath of S. sekhukhuniense extends into two slender, curling ligulae which are absent in S. glaucophyllum. Also included here is a key to the seven currently accepted species of Stylochaeton in southern Africa (South Africa, Eswatini, Zimbabwe and Mozambique).
Key words: bushveld arum, endangered, geocarpy, Sekhukhuneland Centre of Endemism, serpentine, Stylochaetoneae,
taxonomy, ultramafic soil, Zamioculcadoideae
Stylochaeton glaucophyllum Struwig, S.J.Siebert & A.E.van Wyk, sp. nov.
In habit approaching forms of S. borumense with sagittate leaf blades, but differs in the spadix having male and female flowers contiguous and the filaments not thickened (vs. male and female flowers separated by a zone of few to 10 sterile flowers and filaments thickened towards apex). Morphologically most similar to S. sekhukhuniense, differing in having a glabrous petiole (vs. scattered trichomes on petiole immediate distal to petiolar sheath); petiolar sheath not ligulate (vs. distinctly ligulate); leaf blade long, 112–332 mm (vs. shorter, 44–180 mm) with basal and apical lobes linear (vs. elliptic), greenish blue (vs. green); spadix protruding somewhat from spathe-tube (vs. entirely enclosed by spathe-tube).
Etymology:—The specific epithet is a compound word derived from the Greek glaucos = greenish blue or seagreen, dull green, passing into greyish blue + phyllon = leaf (Stearn 1992). It refers to the greenish blue color of the leaves. The generic name is treated as neuter, as this is how it was originally published (Nicolson & Mayo 1984). The local vernacular name in English for S. natalense (Fig. 1) is “bushveld arum” and in Afrikaans bosveldvarkoor. As English and Afrikaans names for the new species we propose “blue bushveld arum” and bloubosveldvarkoor, respectively.
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| Stylochaeton sekhukhuniense, morphology of leaves and inflorescence. A. Basal part of leaves showing the distinctly ligulate petiolar sheaths; note hairs on the part of the petiole above the sheath. B. Petiolar sheaths with curly ligulae, viewed from above. C. Inflorescence with strongly forward curving spathe. D. Inflorescences removed from plant and soil cleaned from basal parts; viewed from different angles. Photographs: A.E. van Wyk (A, C & D) and S.J. Siebert (B). |
Stylochaeton sekhukhuniense Struwig, S.J.Siebert & A.E.van Wyk, sp. nov.
In habit approaching forms of S. borumense with sagittate leaf blades, but differs in the spadix having male and female flowers contiguous and the filaments not thickened (vs. male and female flowers separated by a zone of few to 10 sterile flowers and filaments thickened towards apex). Morphologically most similar to S. glaucophyllum, differing in having scattered trichomes on petiole immediate distal to petiolar sheath (vs. glabrous); petiolar sheath distinctly ligulate (vs. not ligulate); leaf blade short, 44–180 mm (vs. longer, 112–332 mm) with basal and apical lobes elliptic (vs. linear), green (vs. greenish blue); spadix entirely enclosed by spathe-tube (vs. protruding somewhat from spathetube).
Etymology:—The specific epithet “sekhukhuniense” refers to “Sekhukhuneland”, the geographical region to which the species is endemic. The region derives its name from that of the 19th century Bapedi king, Sekhukhune I [ca. 1814–1882] (Raper et al. 2014). As English and Afrikaans names for the new species we propose the name “Sekhukhune bushveld arum” and sekhukhunebosveldvarkoor respectively
Madeleen Struwig, Precious T. Le Roux, Stefan J. Siebert, Abraham E. van Wyk. 2023. Two New Species of Stylochaeton (Araceae: Aroideae) from South Africa. Phytotaxa. 620(1); 1-17. DOI: doi.org/10.11646/phytotaxa.620.1.1
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