Frankenia fruticosa J.C.Manning & Helme, 2014

Manning, J. C. & Helme, N. A., 2014, Frankenia fruticosa (Frankeniaceae), a new dwarf shrub from the Knersvlakte, Western Cape, South African Journal of Botany 91 (10), pp. 84-87 : 85-87

Frankenia fruticosa J.C.Manning & Helme , sp. nov.

Type: South Africa, Western Cape, Vanrhynsdorp (3118): 11 km NE of Lutzville, Moedverloren 208, 3 km NW of old marble mine, (− AD), 20 Nov. 2013, N.A. Helme 7796 ( NBG, holo. ; K, PRE, MO, iso.) .

Rounded, multi-stemmed, densely leafy dwarf shrub to 350 mm high, with numerous short, upright branchlets from thick, gnarled or twisted, woody base up to 80 mm diam., ending in flowering dichasia, young branches reddish with dense white, curly pubescence, later glabrescent with grey bark; internodes as long as leaves, 1.5–3.0 mm long. Leaves opposite–decussate, ascending–incurved, subsessile, allantoid–ericoid, 1.5–2.5 × 0.5–1.0 mm, coarsely punctate, densely scabridulous, ventral surface with densely puberulent longitudinal groove, apex with a small warty apiculus, sheath a fringe of coarse hairs; bracts 2 or 4 in a verticel, similar to leaves; bracteoles 1.0– 1.5 mm long, with broad, flattened petiole partially adnate to sheath. Flowers 1–few in dichasia congested at branch tips, bisexual, unscented. Calyx tubular, induplicate, 5-ribbed, 4–6 mm long, coarsely puberulous outside with white hairs on ribs and densely puberulous in grooves, glabrous inside. Petals 5, narrowly oblong, ± 8 mm long, white with pink claw, claw ± 4 mm long, ligulate, cohering laterally with margins tucked along ligule, ligule linear and longitudinally adnate to claw with truncate apex merging imperceptibly into blade, blade oblong, ±4 × 1 mm, erose. Stamens 6, exserted up to 1 mm beyond mouth of calyx at anthesis, later torn loose at base by ripening fruit and then spreading and exserted ± 3 mm, filaments linear– oblanceolate, ± 7 mm long, slightly expanded and angled in lower half and cohering, filiform above, white flushed pink, anthers subglobose, bipartite, versatile, ± 1 mm long, wine-red, pollen yellow. Ovary ellipsoid, 5-angled or -ribbed by pressure from stamens and petals, ± 1.5 mm long, 6-ovulate with two ovules near base of each of three parietal placentas, funicles erect, shorter than ovules; style terete, up to 3 mm long at anthesis but later elongating to 5 mm, usually sharply kinked at base, 3-branched, branches ± 1 mm long, included at anthesis but later exserted 3–4 mm but never beyond stamens, pink to wine-red, stigmas clavate. Immature capsule ovoid, ± 2 mm long. Immature seeds ellipsoid–fusiform, angled by pressure, ± 1 mm long, smooth; developing rapidly even before flower has withered. Flowering time: November, possibly late October in dry years. Figs. 1 & 2.

3.2.1. Distribution and ecology

A local endemic of the Knersvlakte in southern Namaqualand, Western Cape, Frankenia fruticosa is known thus far only from Moedverloren 208 ( Fig. 3 ), the original, anchor property in the Knersvlakte Biosphere Reserve, managed by CapeNature as a conservation area. The species is locally common on the upper parts of south facing, quartz covered slopes, a habitat that receives significant extra moisture in the form of fog condensation (N. Helme, pers. obs.). The species is absent from many seemingly suitable habitats, and co-occurs with Mesembryanthemum digitatum Aiton (= Dactylopsis digitata (Aiton) N.E.Br. ), Sarcocornia xerophila (TÖlken) A.J. Scott, Gazania othonnites (Thunb.) Less. , and the recently described local endemics Romulea quartzicola J.C.Manning & Goldblatt and Ficinia quartzicola Muasya & Helme. The underlying soils are derived from heavily weathered shales, slightly saline, quick to erode, and rich in gypsum.

3.2.2. Conservation status

The total population is estimated to be 1 000–5 000 plants in a discontinuous but single population over a total area of about 100 ha, and there are no known threats to the population.We therefore suggest a conservation status of Least Threatened ( IUCN, 2001).

3.2.3. Diagnosis

A very distinctive taxon, unique among the southern African species in its gnarled, woody habit, the plants forming compact dwarf shrubs up to 35 cm high, with numerous short, erect branches issuing from a thick, woody base. The small, sausage-shaped leaves, 1.5–2.5 mm long, are densely puberulous with short, white hairs, and narrowly grooved beneath. The flowers are distinctive in their densely puberulous calyx ribs and narrow petals, ± 8 mm long with the blade scarcely wider than the claws, the apex of the ligule merging into the blade. Frankenia fruticosa is unusual in the genus in the relatively few ovules per locule — just six ovules in three pairs, one pair near the base of each of three parietal placentas. Enlargement of the ovary that accompanies early and rapid ripening of the seeds causes the petals and stamens to tear free at the base and to be pushed up to protrude well beyond the mouth of the calyx tube, giving a false impression that the stamens and style are well exserted at anthesis.

Frankenia fruticosa cannot be confused with any of the southern African species, all of which are straggling or prostrate plants. The sausage-shaped leaves resemble those of the two endemic species, F. pomonensis from coastal southern Namibia, and F. repens , which is widespread in coastal areas throughout the Greater Cape Floristic Region, but both these species have significantly larger leaves, 3–7 mm long with the upper surface glabrous, larger flowers with obovate petals 9–11 mm long, a calyx that is either glabrous ( F. pomonensis ) or sparsely hispid ( F. repens ), and numerous ovules, ±20–40 per ovary ( Obermeyer, 1976).

The relationships of this remarkable species remain to be established in view of its distinctive characters, notably the imperceptible grading of the ligule into the petal blade, quite unlike the usual acute ligule of other species of Frankenia , and the reduced number of ovules. In its gnarled, woody habit F. fruticosa resembles the southern South American F. patagonica , which also has a reduced number of ovules on basal– parietal placentas ( Whalen, 1989) but minute, granular leaves. The New World species in particular are variable in the number of ovules ( Whalen, 1989), and a possible relationship with F. fruticosa should be considered.

3.2.4. Additional specimen seen

South Africa, Western Cape: 3118 (Vanrhynsdorp): Moedverloren , (− AD), 3 Oct. 2002, U. Schmiedel 123431 ( HBG) .

Figures

Fig. 1. Frankenia fruticosa, Helme 7796 (NBG). A, calyx; B, petal; C, stamen (adaxial view) and detached anther (abaxial view); D, ovary at anthesis (left) and after pollination (right). Scale:1 mm.Artist: John Manning.

Fig. 2. Frankenia fruticosa, Moedverloren. A, habit (lens cap 50 mm diam.); B–D,detail of inflorescences and flowers.Photographer: Nick Helme.

Fig. 3. Distribution of Frankenia fruticosa.