Notothlaspi viretum Heenan, 2019

Heenan, Peter B., 2019, A taxonomic revision of Notothlaspi (Brassicaceae), a specialist alpine genus from New Zealand, Phytotaxa 399 (3), pp. 248-260 : 256-258

Notothlaspi viretum Heenan , spec. nov. ( Figure 3 )

Distinguished from N. australe by its compact cushions with numerous closely placed rosettes, the lamina green, linear to linear-narrowly lanceolate, 7.0–17.0 mm long and 0.7–2.4 mm wide, and ultramafic habitat.

Holotype:— NEW ZEALAND. Red Hill , Red Hills, Richmond Range, 5500 ft, rock crevice, ultramafic rocks, 31 December 1980, A. P. Druce s.n. ( CHR 366015 !).

Description:—Perennial herb, with short lateral stems, stems 1.0– 1.7 mm diam., usually forming compact cushions of few to numerous rosettes. Leaves 9.0–26.0 mm long, rosulate or spreading on stems; lamina 7.0–17.0 mm long, 0.7– 2.4 mm wide, linear to linear-narrowly lanceolate, green, coriaceous, glabrous on abaxial and adaxial surfaces; margin usually entire, occasionally 1-pinnatafid; apex attenuate, tip obtuse with a prominent hydathode, base attenuate; petiole 2.0–10.0 mm long, often indistinct from lamina. Inflorescence axillary, flowers solitary; peduncle 7–10 mm long, 0.4–1.0 mm diam., ascending, glabrous. Sepals 3.7–4.5 mm long, 1.2–1.5 mm wide, linear-lanceolate, green, glabrous, margin entire, apex subacute, base truncate. Petals 5.5–6.5 mm long, 1.6–2.4 mm wide, white, limb obovate to broadly elliptic, patent to reflexed; apex obtuse; base cuneate, tapering to a 2–3 mm long claw. Stamens 6; filaments linear, two 2.4–4.0 mm long, four 3.4–5.4 mm long; anthers 0.9–1.0 mm long, cream to pale yellow. Ovary 2.2–3.0 mm long, 1.2–1.8 mm wide, compressed, green, glabrous; ovules 5–8 per locule; style 2.0– 2.1 mm long, terete; stigma capitate, 0.4–0.5 mm diam. Silicle 4.3–5.2 mm long, 4.5–5.1 mm wide, green, glabrous, obcordate, angustiseptate; valves keeled, winged, wing c. 0.5 wide at base, up to 2.3 mm wide at apex, wing extended to form an apical notch to silicle; style persistent, up to 1.2 mm long. Seeds 0.8–1.1 mm long, 0.6–0.9 mm wide, orbicular-oblong, brown. Chromosome number 2 n = 90–100. FL Dec–Jan; FT Feb–Apr.

Representative specimens:— NEW ZEALAND. Marlborough. Red Hill basin, Red Hills , P. J. de Lange 3273 & P. B. Heenan, 9 April 1997, AK 232636 !; Red Hill , February 1979, J. Howard s.n. ( CHR 363071 !) ; Red Hill, Red Hills , 14 January 1998, S. Courtney s.n. ( CHR 533022 !/ CHR 533023 !/ CHR 533024 !) ; Red Hills, 9 April 1997, P. B. Heenan & P. J. de Lange s.n. ( CHR 512603 !/ CHR 512597 !/ CHR 512598 !) ; Red Hills summit, February 1979, J. Howard s.n. ( WELT SP092803 !) ; Red Hill, Red Hills , 31 December 1980, A. P. Druce s.n. ( CHR 366016 !) .

Distribution and habitats:— New Zealand, endemic. Notothlaspi viretum is known only from the summit of Red Hill, Red Hills, Marlborough, northern South Island ( Figure 5). It is sympatric with the more widespread N. australe in the Red Hills. The Red Hills ultramafic area has high genus and phylogenetic endemism ( Millar et al. 2017), and includes the following endemic species: Carex devia Cheeseman (1883: 301) , Chionochloa defracta Connor in Connor & Edgar (1987: 164), Festuca ultramafica Connor (1998: 363) , Geranium rubricum Heenan & Courtney (2017: 90– 93) , Leptinella pyrethrifolia var. linearifolia ( Cheeseman 1883: 299) Lloyd & Webb (1987: 103) , Montia racemosa ( Buchanan 1871: 210) Heenan (2007: 438) , and Poa acicularifolia ssp. ophitalis Edgar (1986: 444) .

Notothlaspi viretum occurs among rocky outcrops, on open, sparsely vegetated, stable to semi-stable scree, coarse sand, and soil derived from ultramafic harzburgite rock at an elevation of 1540–1700 m.

Etymology:—The specific epithet viretum , meaning grass green, refers to the color of the leaves.

Conservation status:— Notothlaspi viretum is assessed as having a conservation status of Threatened, Nationally Critical ( de Lange et al. 2018, as Notothlaspi (a) (CHR 363071; Red Hills)). The area of occupancy is assessed as being less than or equal to 1.0 hectare, the population is stable and at one location. Hybridisation may pose a long term threat as N. viretum is sympatric with N. australe and plants possibly representing hybrids were observed during the site visit in April 1997.

Figures

FIGURE 3. Notothlaspi viretum. A. Young plants of N. viretum (top) and N. australe (bottom) growing together among the summit rocks of Red Hill, Red Hills, Marlborough. B. Numerous densely placed rosettes forming a compact cushion with grass-green leaves. C. Fruiting plant with characteristic linear, grass-green leaves.