Aloe davyana var. subolifera, Groenewald, 1939

Smith, Gideon F., Klopper, Ronell R., Crouch, Neil R. & Figueiredo, Estrela, 2021, Reinstatement of Aloe davyana var. subolifera (Asphodelaceae subfam. Alooideae), a distinctive variety of an endemic South African aloe, Phytotaxa 482 (2), pp. 208-212 : 209-211

Nomenclature of Aloe davyana var. subolifera

Aloe davyana var. subolifera Groenewald (1939 : t. 732). Also treated in: Groenewald (1941: 65, 125), Reynolds (1950: 235), Jeppe (1969: 95), Bornman & Hardy (1971: 97), Jacobsen (1977: 77), Jacobsen (1986: 155). Type:—[ SOUTH AFRICA]. Transvaal [the locality is in the present-day Limpopo province], Pretoria Distr., near Pienaar’s River [Pienaarsrivier, ca. 55 km north of Pretoria], August 1936, F.[Z.] van der Merwe in Nat. Herb. 22816 (holotype PRE PRE0084275-0!).

Nomenclatural note on the type of the name Aloe davyana var. subolifera :— Reynolds (1950: 235) and Glen & Hardy (2000: 56) cite “ F.[Z.] van der Merwe in Nat. Herb. 22816 ” simply as “Type”. It is here corrected to holotype.

Amplified description of Aloe davyana :

Reinstatement of A. davyana var. subolifera necessitates the amendment of the description of A. davyana (see Smith et al. 2020) as follows:

Description: —Acaulescent plants or rarely with short stem; rosettes solitary or sometimes shortly suckering to form groups of 2–4, or up to 20 ( var. subolifera ). Leaves up to 30 cm long (20–25 cm in var. subolifera ), 6–8 cm wide ( var. davyana ) or 3–5 cm wide ( var. subolifera ). Inflorescences 0.5–1.4 m high (up to 1.2 m high in var. davyana ). Pedicels 20–25 mm long ( var. davyana ) or 8–11(–15) mm long ( var. subolifera ). Raceme apically dense, basally laxer or lax throughout ( var. subolifera ), 15–20 × 7–8 cm ( var. davyana ) or 9–12 × 4–6 cm ( var. subolifera ). Flowers: perianth nearly white to pale flesh-pink ( var. subolifera ) to dull brick-red, with greenish to greyish white stripes, 22–35 mm long [32–35 mm long in var. davyana ; (22–)25–27(–30) mm long in var. subolifera ]. Chromosome number (of both varieties): 2 n = 14 ( Groenewald 1941: 167).

The other characters of A. davyana var. subolifera are similar to those of A. davyana var. davyana .

Flowering time: — Aloe davyana var. subolifera flowers from (May–)June through to September.

Habitat: — Aloe davyana var. subolifera occurs on red sands or black turf in comparatively open, grassy patches in savanna, or in the dappled shade of deciduous trees.

Distribution: —The main centre of distribution of A. davyana var. subolifera is about 50 km due north to slightly northwest of Pretoria, around Pienaarsrivier in the Limpopo province ( Fig. 2 ).

Aloe davyana var. subolifera occurs naturally in a comparatively small area that is, at least in the south, impacted by urban sprawl and land transformation for the establishment of informal housing. The area is fortunately protected in some private conservation areas in the north, such as at Lunikhy Game Lodge and Wolfhuiskraal, and to the southeast in the Dinokeng Game Reserve, although the latter area is just beyond the main natural distribution range of A. davyana var. subolifera . However, in these reserves, which often focus on game and livestock farming, natural fires are customarily excluded. Under such conditions the integrity of ecosystems and the configuration of plant diversity can be negatively impacted.

In the African bushveld (savanna), including in the Waterberg close to the type locality of A. davyana var. subolifera (Wadley 2019) , several disturbances, such as fire and herbivory by large mammals, including the African elephant, Loxodonta africana ( Blumenbach, 1797) , influence, inter alia, the integrity of ecosystems and the composition of their vegetation components, as well as the configuration of plant diversity ( Van Staden et al. 2016 –2017). The intensity of natural fires, which mostly start after lightning strikes in summer, typically varies depending on the season in which it occurs, the dry winter or wet summer. Furthermore, given intensive agricultural activities in the Waterberg and adjacent parts of the bushveld, including both game and livestock farming, as well as crop planting, efforts to exclude fire have been implemented for some years. Such practices have resulted in bush encroachment and the almost invariably concomitant densification of the woody component of the flora; the often simultaneous densification of the grass layer can yield the vegetation moribund ( Van Staden et al. 2016 –2017, Van Staden et al. 2018). This influences the population dynamics of low-growing succulents, including of A. davyana var. subolifera . Processes that disturb biome integrity, including fire and the impact of herbivores, are complex and aspects such as climate shifts and physical topographical features additionally and interactively shape ecosystem functioning (Van Staden et al. 2018).

Additional specimens examined: — SOUTH AFRICA, Gauteng: Pretoria, Hammanskraal , 18 July 1914, I. B . Pole Evans 28 ( PRE!); 20 miles beyond Pretoria , fl. 4 July 1934, G. G . Smith 168 & 169 ( PRE!); 4 miles N of Pretoria, 30 August 1953, L. N . Prosser 1863 ( PRE!) ; Limpopo, Pienaar’s River , 16 August 1917, I. B . Pole Evans H 15698 ( PRE!); Beyond Hammanskraal, 28–38 miles from Pretoria , May 1935, A. A . Obermeyer & I . Verdoorn 1 ( PRE!); Pienaar’s River , 4 August 1935, G. W . Reynolds 1498 ( PRE!) .

Figures

FIGURE 2. Map of the natural geographical distribution ranges of Aloe davyana var. davyana [orange shading] and A. davyana var. subolifera [red shading].