Periglossum podoptyches Nicholas & Bester, 2016

Bester, Stoffel P. & Nicholas, Ashley, 2016, Periglossum podoptyches (Apocynaceae-Asclepiadoideae), a new species from KwaZulu-Natal province, South Africa, Phytotaxa 282 (1), pp. 28-36 : 30-33

Periglossum podoptyches Nicholas & Bester spec. nov. ( Figs. 1–3 ).

Periglossum podoptyches is morphologically closest to P. mackenii and P. kassnerianum from which it differs in the presence of folded flaps of tissue at the base of the restricted basal stalk of the staminal corona lobes. Further it does not have a “T”-shaped slit on the ventral surface of the staminal corona lobe which is instead solid and smooth.

Type: — SOUTH AFRICA. KwaZulu-Natal Province, Dannhauser area, Fairbreeze farm, 26 December 1984, A. M. Ngwenya 107 (holotype, NH!; isotype, PRE!) ( Fig. 2 ) .

Perennial, geophytic herb, exuding milky latex where damaged. Underground organ a cylindrical swollen tuber with white flesh, 43.9–62.3 × 9.5–14.7 mm; neck 11.6–40.6 mm long. Stems solitary, erect, terete, grooved, mostly unbranched, 160–286(–440) mm tall, internodes 8.3–43.2 mm long, glabrous to bifariously pubescent. Leaves opposite, simple, spreading-erect, horizontal or slightly pointing downward; petiole sessile or subsessile, up to 2.5(–4.0) mm long; lamina linear to almost filiform, 22–95(–132) × (0.6–) 0.8–5.5 mm, base attenuate, margins smooth and revolute, apex acute, midrib prominent below, glabrous; bottom leaves caducous. Inflorescences: 1–4 extra-axillary along the upper part of the stem, globose umbels 12–18 mm in diameter, 4–15(–20)-flowered; peduncle erect, 8.9–22.6(–35) mm long, bracts filiform, ca. 1.4 × 0.2 mm. Flowers sessile to subsessile, 6.6–7.6 × 6–8.7 mm wide at the top, pedicel to 0.4 mm long. Calyx reaching beyond the corolla sinuses; lobes lanceolate to ovate, 4.1–4.5(–6.0) × (1.2–)1.3–1.7(– 2.5) mm, ventral surface glabrous, dorsal surface pilose pubescent; small, lanceolate colleters opposite the sinuses. Corolla 5-lobed, tubular, fused in basal 5th (0.9–1.9 mm) or almost free to the base; lobes erect, oblong, linear-oblong to lanceolate, narrowly deltate or obovate, 5.9–7.8(–9) × 1.6–2.5 mm, apex with margins inflexed and connivent to form a small sharp point, notched or rounded, margins hyaline, revolute and wavy in the upper part, dorsal surface glabrous, ventral surface puberulous especially towards the apex, variable in coloration from white with brown stripes (Ngwenya 107), green or whitish tinged with purple (Ngwenya 471), purplish-green (Ngwenya 1107) or plain green (Bester 10585). Corona in 2 unequal series, produced at the gynostegial column-base. Staminal corona 5-merous, fused basally; lobes erect, dorsi-ventrally flattened, 4.8–6.0 mm tall, blade elliptic to ovate, (3.0–)3.7–4.4(–4.5) × 1.0–2.1(– 2.2) mm, sometimes shortly stipitate, stipe 0.5–1.0(–2.0) × 0.3–1.2 mm, base obtuse ratio of stalk to blade 1:6–8, inner face smooth, apical portion sometimes convex with 2 obscure longitudinal ridges, margins revolute (as if pinched, then apical section ca. half as broad as basal section) and concave on the outer surface or featureless, apex obtuse or rounded, sometimes slightly emarginate, basally tapering into a short stalk which has two laterally placed, paddleshaped or foot-shaped, irregularly margined, sometimes lobular, inflexed and pressed flaps of tissue 0.3–0.6 × 0.3–0.6 mm and distinctly longitudinally ridged, margins sometimes slightly reflexed below, much reflexed apically, outer surface smooth and featureless. Interstaminal corona 5-merous; lobes short, dentate-filiform, 0.3–0.7 × 0.1–1.7 mm. Staminal-column arising from the base of the corolla, subglobose with anther-wings and anther-appendages forming a frilly cap over the style-apex, 2.8–3.0 × 2.4–2.7 mm. Androecium: anthers 1.4–2.5(–4.0) × 0.8–1.49(–1.8) mm; anther-wings 0.4–0.6 mm tall produced at the very apex of the anthers (above the anther-sacs), extending 0.4–0.6 mm from gynostegial column, (0.3–)0.4–0.6 × 0.1–0.3(–0.7) mm, gynostegial-groove wide 0.2–0.3(–0.5) mm and gutter-like; anther-appendages sagittate-ovate, folded basally and connivent at the acute apex, 0.8–1.7(–1.8) × 0.1–1.0(–1.3) mm, held well above the style-apex on 0.2–0.5 mm long basal stalk. Pollinarium: pollinia solitary and pendulous in each anther-sac, oblong-curved or boomerang-shaped, 0.83–0.95(–1.20) × 0.23–0.25(–0.30) mm, attached apically to the translators, distal end forming a flat germination zone; caudicle long, thin, sinuous, 1.3–1.5(–1.7) × (0.03–) 0.08–0.11 mm, narrowing to 0.03–0.07 mm wide where attached to clip, and 0.20–0.26 mm broadened and excavated at the base where it is attached to the pollinia; corpusculum diamond-shaped to ovate, 0.2–0.4 × 0.08 × 0.09(–0.21) mm, with 2 downwardly pointing paddle-like wings ca. 5 × 65–80 μm. Gynoecium: style-apex small and truncated. Follicles solitary, erect, narrowly fusiform, 68.6–72.2 × 4.8–5.9(–6.0) mm, apex attenuately beaked and sometimes slightly curved, surface smooth, tomentose when young, sparsely hairy when more mature. Seeds not seen.

Phenology:—Plants flowers in November to January with follicles maturing about a month afterwards.

Etymology:—The genus name is derived from the Greek peri - (= around) and glossum (= tongue), in reference to the tongue-like corolla and staminal corona lobes that surround the gynostegium. The epithet is derived from the Greek podion (= foot) and ptyches (= folds) in reference to the “foot-like” folds of tissue on the ventral side of the base of the staminal corona lobe ( Nicholas 1999).

Distribution and habitat:—South African endemic (KwaZulu-Natal Province, Dannhauser and Utrecht Districts) ( Fig. 4 ). Plants are restricted to dry grasslands of ± level plains and floodplains, growing in well drained loam and sometimes rocky to stony soil. The habitat is found in the Sub-Escarpment Grassland Bioregion (vegetation types: Northern KwaZulu-Natal Moist Grassland; Income Sandy Grassland) (Muchina & Rutherford 2006).

Conservation assessment:—So far this species is only known from six collections within four locations in a fairly well-collected province. Label information indicates that the species is locally rare where it occurs. Some were collected in a densely populated human rural settlement (Ngwenya 471) and another was found growing in severely overgrazed grassland (Ngwenya 107). Another specimen (Ngwenya 1107) was collected in an already transformed habitat between blue gum trees and ploughed land, and label information indicates its presence as rare.All of these annotations indicate that most material came from already transformed sites and may present conservation challenges.

Seeds—although wind-dispersed—do not travel far. From personal observation in a number of Asclepiadoideae the coma detaches from the seed within a short time (less than 5 minutes) after being released from the follicle. In the absence of wind the seed will fall and germinate within the population; with strong wind present the seed could travel a short distance—a few hundred meters at most. Flies have been measured to fly between 1.6–3.2 km ( Townsend 2016), bees on average 3 km, but up to 9 km from the hive ( Eckert 1933), and wasps up to 1 km ( Cranshaw 2012). The specialised insect-pollination mechanism ( Johnson & Steiner 2000, Shuttleworth & Johnson 2008, 2009), coupled with the minimum of 22 km distance between the two closest subpopulations, each location is likely to be a different sub-population thus rendering sub-populations and locations to be the same in this case. This species has been recorded from 4 locations (=sub-populations). The calculated EOO is 1 411 km 2. As there are no indications of declining populations, but observations at one of the locations indicate it as being transformed (Ngwenya pers. com. 2016) the conservation status should be deemed Vulnerable (VU D2) according to the IUCN (2001) criteria (Assessors SP Bester & JE Victor 17/02/2016). In places this species establishes well in disturbed (e.g. edges of ploughed lands) areas, and thus this disturbance is not seen as an immediate threat in this case.

Figures

FIGURE 1. Periglossum podoptyches. A, apical portion of the stem with leaves and inflorescences. B, tuber. C, fully open flower in side view. D, dissected basal part of flower with corolla and corona lobes removed showing the gynostegial column. E, ventral flaps at base of staminal corona lobes with reduced interstaminal corona lobes on either side of basal foot of staminal corona lobe. F–H, staminal corona lobe; F, side view; G, dorsal view; H, ventral view with basal flaps. I, Pollinarium. J, immature fruit. Vouchers: A, B, A. Ngwenya 107 (NH); D–I, S.P. Bester 10585 (PRE); C, J, L.E. Codd 114 (PRE). Scale bar: A, B, J = 10 mm; C, F, G, H = 1 mm; D = 0.5 mm; E, I = 0.2 mm. Artist: G.S. Condy.

FIGURE 2. Scan of the holotype of Periglossum podoptyches (Ngwenya 107, NH)

FIGURE 3. Comparison of the face (ventral-side) of the staminal corona lobes of A, Periglossum angustifolium; B, P. mackenii; and C, P. podoptyches. Note the T-shaped slits on and thickened apical portion in A & B in contrast to the featureless blade of C. Vouchers:A, E.J. Moll 3464 (PRE!); B, S.P. Bester 10817 (PRE!); C, S.P. Bester 10585 (PRE!). Scale bar: 1 mm. Artist: G.S. Condy.

FIGURE 4. Map of the known distribution of Periglossum podoptyches.