Pelargonium auriculipetalum E. M. Marais 2024, sp. nov.
Creators: name: Marais, Elizabeth M.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Geraniales
Geraniaceae
Pelargonium
Pelargonium auriculipetalum

description: Pelargonium auriculipetalum E.M.Marais, sp. nov. (Fig. 1).
Diagnosis:— Similar to P. triphyllum because in both species the petals are ligulate with claws auriculate, stamens straight, longer than the sepals, almost similar in length and protruding from the flower. They differ in that P. auriculipetalum has white to pale pink flowers and pinnately to bipinnately compound leaves, although juvenile leaves are often simple. The flowers of P. triphyllum are pink to a striking bright pink and leaves vary from simple or three-parted to many-parted. However, compound leaves are never as finely divided as in the case of P. auriculipetalum.
Type:— SOUTH AFRICA. Western Cape: on the Gydo–Citrusdal road, next to the farm Rocklands, (3319 AB), 1 September 1990, E. M. Marais 371 (holotype NBG!; isotypes K!, PRE!).
A deciduous geophyte 110–130 mm tall when in flower. Tuber: turnip-shaped, elongated or moniliform root covered with flaking dark brown periderms, 20–30 mm long and 12–25 mm diam. Leaves: radical, erecto-patent, regularly pinnately to bipinnately compound, petiolate; lamina elliptic in outline, 25–35 × 15–25 mm, pinnae irregularly deeply incised, segments 1–2 mm wide, apices acute, ending in one or two stiff hairs, adaxially and abaxially sparsely hirsute with appressed stiff hairs, sparsely interspersed with short glandular hairs, margins sparsely ciliate; petiole rigid, erect, 35–65 mm long and 1.2 mm in diam., green, covered with appressed curly hairs interspersed with stiff hairs and short and long glandular hairs; stipules narrowly triangular, ciliate, 12–22 × ± 1 mm, white, adnate to petiole, apices free. Inflorescence: scape 10–40 mm long, pale green, hirsute with distally appressed stiff hairs and short curly hairs interspersed with short and long glandular hairs, branched, bearing 2–5 pseudo-umbellets with 6–8 flowers each; peduncles 80–110 mm long, 2 mm in diam., brownish green, densely hirsute with distally appressed stiff hairs and short curly hairs interspersed with short and long glandular hairs; bracts inconspicuous, narrowly triangular, 3–6 × 1.5 mm, abaxially hirsute with distally appressed hairs, densely interspersed with glandular hairs; flower buds, flowers and fruits erect. Pedicel ± 0.5 mm long. Hypanthium 5–11 mm long, 1.0–1.5 times the length of the sepals, reddish brown, densely covered with glandular hairs interspersed with appressed curly hairs. Sepals 5, posterior one erect, others recurved, lanceolate, apices acute, 5–9 × 0.8–2.2 mm, pale reddish brown with margins white to pink, abaxially densely covered with glandular hairs interspersed with appressed curly hairs. Petals 5, white to pale pink, patent during anthesis; posterior two with dark pink markings, ligulate, 9.5–18.0 × 1.5–2.5 mm, length/width ratio 4.0–7.2; claws auriculate, 4–6 mm long, apices rounded to emarginated; anterior three with faint V-shaped markings, unguiculate-spathulate, 6.0–13.5 × 1.3–2.0 mm, claws filiform 2.0– 3.5 mm long, apices rounded. Stamens 10, basally connate, staminal column 2–3 mm long, smooth, white, fertile stamens 5, posterior filament 9–11 mm long, lateral two filaments 9.5–11.0 mm long, anterior two filaments 9.5–11.5 mm long, 1.2–1.9 times the length of the sepals, protrude from the flower, apices of free filaments pale pink, remaining straight during anthesis, staminodes 3.5–4.0 mm long; anthers pink, ± 2 mm long, pollen orange. Gynoecium: ovary 2.8–4.0 mm long; style 1.5–3.5 mm long, dark pink; stigma with 5 recurved branches, 1.0– 1.2 mm long, dark pink. Fruit: bases of mericarps 4 mm long, with glandular hairs, tails 12–13 mm long. Chromosome number: 2n=18 Focke Albers, pers. comm.).
Flowering period:— October to December.
Habitat:— Occurs in dry stony areas in fynbos on sandstone or in renosterbosveld on clay, in areas with an annual rainfall of 100–200 mm mainly during the winter months.
Distribution:— Occurs in the Kouebokkeveld and around the Witteberge (Fig. 2). This distribution overlaps with that of P. triphyllum, although the latter has a much larger distribution area from Nieuwoudtville in the north to Riviersonderend in the south and an extention to Aberdeen in the east (Fig. 2). Collections of P. triphyllum were usually made at higher elevations (Marais 1994) in areas with an annual precipitation higher than 400 mm. Both species occur in fynbos on sandstone derived soil or on clay or shale bands and both flower from October to December.
Diagnostic characters:— Pelargonium auriculipetalum is a deciduous geophyte with small white to pale pink flowers, ligulate petals with claws auriculate, five fertile stamens, stamens remaining straight during anthesis, almost similar in length and always longer than the sepals and pinnately to bipinnately compound leaves.
Conservation status:— Because of extensive agricultural activities in the Kouebokkeveld the areas with natural vegetation are declining and this species could be under threat. However, more in depth exploration is needed for the correct assessment of the extinction risk of this species. Therefore, according to IUCN (2024) guidelines, it is previously indicated as Data Deficient (DD).
Etymology:— The specific epithet refers to the auriculate claws of the petals (Latin auriculatus, furnished with ear-like appendages).
Notes:— The flowers of P. auriculipetalum and those of P. triphyllum are very similar. In both species the posterior petals are ligulate with auriculate claws, both have relatively short hypanthia (5–19 mm long) and long stamens protruding from the flower. The five fertile stamens are almost similar in length and are always longer than the sepals. The stamens remain straight during anthesis. In both species the scape is branched with 2–4(–5) pseudo-umbellets and (3–)6–8(–10) flowers per pseudo-umbellets, and they have the same indumentum on the leaves, scape, peduncle, hypanthia and sepals. The structure of the pollen grains of both species is very similar. The equatorial diameter of the pollen grains in both species lies between 53–74 μm (P. triphyllum: 60–68 μm; Marais 1994 and P. auriculipetalum: 53–74 μm) and the structure of the tectum in both species can be described as striate-reticulate (Marais 1994). However, they differ with regard to flower colour, leave shape and chromosome numbers. In P. auriculipetalum 2n=18 (Focke Albers, pers. comm.) and in P. triphyllum 2n=20 (Gibby et al. 1996; Touloumenidou et al. 2004).
The ligulate petals and the long stamens of P. auriculipetalum and P. triphyllum resemble those of P. auritum (Linnaeus) Willdenow (1800: 644), although in the latter the staminal column is papillate whereas in the first-mentioned two species the column is smooth (Marais 1994).
Additional specimens examined:— SOUTH AFRICA, Western Cape: Ondertuin, Kouebokkeveld, (3219 CC), December 1978, Hanekom 2522 (PRE); farm Tweefontein, Kouebokkeveld (3219 CD), 22 November 1975, A. E. Cillie s.n. (STEU); 15 November 1985, E. M. Marais 187 (STEU); Rocklands, on Gydo Pass–Citrusdal road (3319 AB), 1 September 1990, E. M. Marais 372 (STEU); on top of Bantamskop, Witteberg (3320 BC), 20 October 1989, E. M. Marais 350, 351, 352, 353 (STEU).
description: Published as part of Marais, Elizabeth M., 2024, Three new species of Pelargonium, section Hoarea (Geraniaceae) from the Western Cape Province, South Africa, pp. 69-78 in Phytotaxa 675 (1) on pages 70-73, DOI: 10.11646/phytotaxa.675.1.6, http://zenodo.org/record/14521998