Erica hessequae R. D. Hoekstra, 2025

Hoekstra, Rendert D., Musker, Seth D., Pirie, Michael D. & Vlok, Jan H. J., 2025, An integrative approach to alpha taxonomy in Erica L. (Ericaceae) with three new species from the Western Cape, South Africa, PhytoKeys 257, pp. 95-117 : 95-117

Erica hessequae R. D. Hoekstra sp. nov.

Fig. 5

Link.

WFO: https://list.worldfloraonline.org/wfo-1000079210.

Type.

South Africa • Western Cape, 3321 CD (Sandkraal): Langeberg Range, Romanskraal north of Albertinia, north-facing slopes west of Skoorsteen Peak , 1165 m, 33.945°S, 21.482°E, 23 December 2023, R. D. Hoekstra 181 ( NBG, holotype; BG, isotype [2088580]) .

Diagnosis.

Erica hessequae matches characteristics exhibited in E. hispidula , E. oakesiorum , E. rivularis , E. tegetiformis , E. umbratica and E. woodii . It can be distinguished from all these taxa by its ovate leaves (linear, linear-lanceolate or lanceolate in all). It is further distinguished by its glandular pedicel, sepals, bract and bracteoles (all eglandular in E. magistrati , E. oakesiorum and E. tegetiformis ); by its subcapitate stigma (peltate in E. hispidula ; simple in E. rivularis and E. tegetiformis ), and by its densely lanate ovary (shortly hispid in E. hispidula , E. oakesiorum , E. rivularis , E. woodii and E. umbratica ).

Description.

Semi-spreading shrublet up to 80 cm tall. Branches twiggy, glabrous to puberulous; secondary branches ascending, hispid with a mix of simple, eglandular hairs and stipitate glands. Leaves 3 - nate, erect, ovate, blades 4.0–5.0 × 1.5–2.5 mm, acute, open-backed; adaxially slightly convex, hispidulous when young with simple, eglandular hairs mixed with stipitate and sessile glands, glabrescent, margins thickened, revolute; abaxially deeply sulcate, pale, densely hispidulous with simple, eglandular hairs; petiole 0.8–1.2 mm long, hispidulous and glandular as for adaxial leaf surface, not decurrent. Inflorescence of 3 - nate flowers, terminal on secondary and side branches; pedicel 4.0– 5.5 mm long, pale creamy green turning red-purplish with exposure to sun, stipitate-glandular, viscid; bracteoles 2, median, lanceolate, ± 1.5 × 0.5 mm, acute, creamy white to dark pink, leathery, margins densely sessile-glandular, abaxially sparsely hispid towards apex and along basal margin, adaxially glabrous; bract partially recaulescent, sub-median, ovate to lanceolate, ± 0.5 × 1.5 mm long, acute, creamy white to dark pink, leathery, margins densely sessile-glandular, abaxially sparsely hispid towards apex and along basal margin, adaxially glabrous. Calyx 4 - lobed; sepals adpressed to corolla, ovate, 2.0–2.5 × 1.0– 1.5 mm, creamy white / yellow with green tips, leathery; margins densely sessile-glandular, revolute towards apex; abaxially sulcate, with occasional stalked glands and sparsely hispidulous with simple, eglandular hairs within sulcus and at base, otherwise glabrous, viscid; adaxially glabrous, midrib slightly raised. Corolla 4 - lobed, cyathiform to shortly urceolate, throat constricted, 3.5–4.5 × 3.0–4.0 mm, creamy white, glabrous, viscid, occasionally with stalked glands adjacent to sepals; lobes recurved, 0.75–1.25 mm long, obtuse, margins smooth. Stamens 8, free, manifest to exserted, filaments flat, 2.5–3.0 mm long, glabrous, white turning dark reddish pink towards apex, apically kyphotic; anthers cuneate, 0.7–0.8 mm long, brown, dorsifixed at base, bipartite, thecae erect, ventral surface golden brown and shortly scabrous; awns ± 0.4 mm long, thin, laterally fixed to apex of filaments, simple or rarely with one or two basal barbs, reddish brown; pores round, ± 0.4 mm long. Ovary 4 - locular, turbinate, ± 1.0 mm long, dark purple, densely lanate with simple, white, eglandular hairs; ovules 15–20 per locule; placenta apical; nectaries basal, green to black; style ± 3.5 mm long, glabrous, pale pink above but white towards base, exserted; stigma dark pink to purplish, subcapitate. Fruit and seeds not seen. Flowering time: December to January.

Distribution and habitat.

Erica hessequae is only known from two localities, some 4 km apart, on the mountains surrounding Romanskraal north of Albertinia — one along the ridgeline leading up to a plateau mountain west of Skoorsteen Peak, the other on Langeberg Peak. It appears to be confined to high-elevation ridgelines where it grows amongst craggy rocks in North and South Langeberg Sandstone Fynbos ( Mucina and Rutherford 2006). It has only been observed at altitudes above 1100 m.

Threat status.

Erica hessequae appears to be a naturally rare, range-restricted species. There are only two records of the species, one plant having been observed on Langeberg Peak and two west of Skoorsteen Peak. Limited surveys performed in the surrounding area have failed to reveal additional localities. While alien vegetation is present in the region, favouring middle, south-facing slopes, neither location is yet threatened by invasive species. The plants examined at both localities demonstrated a reseeding regeneration strategy, which may represent a vulnerability to too-frequent fires. Erica hessequae was found to have an AOO of 8.00 km 2 and an EOO of 8.00 km 2. Unfortunately, its habitat is remote and not easily accessible, making estimation of the population size difficult in the absence of more systematic surveys. Until more data can be collected, current conservative estimates put the total population size at fewer than 50 mature individuals. Based on this estimate, an IUCN (2012) category Critically Endangered (CR) under criterion D is recommended.

Pollination syndrome.

The small, open cup-shaped flowers of Erica hessequae have well-developed nectaries and anther appendages, suggesting entomophily. The corolla is remarkably viscid and thus likely to trap crawling and flying insects that would need to land on the surface to effectuate pollination. Therefore, small and medium-sized flying insects that avoid trapping by landing on the recurved adaxial lobes or by entering the corolla through the mouth are the most likely pollinators of this species, although no clear interaction with pollinators has been observed. The lack of a peltate stigma and the fact that pollen is not released in a cloud after manipulation make anemophily highly unlikely.

Etymology.

Erica hessequae is named for the Hessequa clan which occupied most of the modern-day Hessequa municipal area encompassing the Eastern Langeberg Range between the Tradouw Pass and Gourits River.

Subgeneric classification.

Erica hessequae could be placed in section Ceramia ( Guthrie & Bolus, 1905) by its glabrous, pitcher-shaped corolla and terminal inflorescence.

Notes on morphology and phylogeny.

Phylogenetic data suggest that E. macrophylla and E. ocellata (sect. Ceramia ) are closely related to E. hessequae . While there are morphological similarities among these three Langeberg-endemic taxa, the former two are readily distinguishable by their muticous anthers. In addition, E. macrophylla has a more elongate, urceolate or tubular corolla with a more constricted throat as compared to the stouter bell- to cup-shaped corolla of E. hessequae . Erica ocellata is distinct in having a capitate, 6 - to 10 - flowered inflorescence (terminal and 3 - nate in E. hessequae ) with significantly shorter pedicels and sepals as compared to E. hessequae .

Beyond character matching and phylogenetic relatedness, Erica hessequae bears an overall morphological similarity to E. grata and E. cordata , two other species found in the Langeberg. Erica hessequae and E. grata are restricted to the Langeberg Range whilst E. cordata has a wider distribution. Erica hessequae can be distinguished from E. grata by its viscid (as opposed to dry), creamy white (as opposed to light- to red-pink) corolla with a less pronounced constriction at the throat, and by its more densely hairy, lanate (as opposed to hispid) ovary; and from E. cordata by its awned (as opposed to muticous) anthers and subcapitate (as opposed to capitate to peltate) stigma. The leaves in E. grata are usually narrower and more lanceolate with less markedly revolute margins than those of E. hessequae , and it is usually a laxer, upright shrublet preferring wet, south-facing lower to middle slopes. Erica cordata is also mostly upright in habit with softer, shorter side branches. In contrast, Erica hessequae has hard ligneous stems and main branches, a semi-spreading, rounded habit, and preference for high-altitude craggy peaks.

Additional specimens examined.

Western Cape, 3321 CD (Sandkraal): Langeberg Mtns, summit of Unnamed Peak (Trig Beacon 45) east of the Langkloof, 1506 m, 33°57.037'S, 21°26.257'E, 22 February 2003, R. C. Turner 701 (NBG).

Figures

Figure 5. Erica hessequae R. D. Hoekstra A multiple inflorescences B single inflorescence C calyx and pedicel D dissected flower showing androecium E dissected flower showing ovary F whole plant in situ. Voucher R. D. Hoekstra 181 (NBG).