Lepidium crassum, Lange & Heenan & Houliston & Rolfe & Mitchell, 2013

Lange, P. J. de, Heenan, P. B., Houliston, G. J., Rolfe, J. R. & Mitchell, A. D., 2013, New Lepidium (Brassicaceae) from New Zealand, PhytoKeys 24, pp. 1-147 : 32-36

Lepidium crassum sp. nov.

A L. oleraceo habitu temporali, caulibus ad caudicem lignosum emorientibus, foliis crasse coriaceis, distincte petiolatis, late ellipticis, ellipticis vel obovatis, apicibus obtusis vel truncatis, marginibus saepe duplicato-serratis, siliculis orbiculatis vel orbiculato-rhomboideis, et sequentia nucleotidorum DNA distinguenda.

Holotype.

New Zealand ( Fig. 33 ): Otago Land District, Otago Peninsula, Aramoana, Mole, open sites among stones and rocks at the edge of the road down mole and in car park, 26 November 2009, P. B. Heenan s.n., CHR 609777A! Isotype: CHR 609777B!

Etymology.

The specific epithet ' crassum ' from the Latin for ‘thick’ refers to the distinctly thick and fleshy leaves of this species.

Description

( Figs 34 -37 ). Tap-rooted, strongly pungent smelling, perennial herb. Growth habit dense, stems closely placed, up to 50 cm tall, arising from underground woody stems. Stems upright to spreading, stout, short, rigid; mature stems woody, 100-400 × 10-12 mm, often devoid of foliage on middle and lower parts of stems, new stems 50-200 × 4-5 mm, leafy, glabrous. Leaves glabrous, coriaceous, green, undulate, rosette and stem leaves usually withering, variable in size and shape. Leaves of young and vigorous plants and stems: lamina 50-90 × 17-35 mm, broadly elliptic, elliptic to obovate; apex obtuse to truncate, often with up to 3 or 4 teeth; margin singly or doubly crenate, with 15-32 pairs of teeth; teeth up to 3.5 mm deep, sometimes overlapping, often protruding beyond leaf outline; base cuneate, petiole usually distinct; petiole up to 35.0 × 3.0-6.0 mm, channelled. Leaves of mature plants and cauline stems: lamina 15-45 × 6-15 mm, broadly elliptic, elliptic-obovate to obovate-oblong; apex obtuse to truncate, often with up to 3 or 4 teeth; margin singly crenate in upper half, teeth often protruding from leaf outline, with 5-10 pairs of teeth; teeth up to 1.2 mm deep, not overlapping, often protruding beyond leaf outline; base cuneate, sometimes narrowly so, usually tapering to ± distinct petiole; petiole 5-12 × 1.6-2.3 mm, channelled. Inflorescence terminal and lateral, racemose, 15-60 mm long, rachis 0.7-1.2 mm diam., glabrous; pedicels 4-7 mm long, erecto-patent, glabrous. Flowers 4.0-5.0 mm diam. Sepals 4, 1.3-1.6 mm long, saccate, overlapping at base, green, apex obtuse, margin white, shape dimorphic; lateral sepals broad, 1.4-1.5 mm diam., orbicular, abaxial surface often hairy, hairs 0.2-0.5 mm long; median sepals narrow, 1.0-1.3 mm diam., broadly elliptic, glabrous. Petals white, 1.8-2.0 × 1.0-1.1 mm, spreading, claw 0.6-0.8 mm long; limb broadly elliptic to orbicular, apex obtuse to rounded. Stamens 4; filaments 1.2-1.6 mm long, base 0.4-0.5 mm diam., equal; anthers 0.4-0.6 mm long. Ovary 1.0-1.6 × 0.9-1.1 mm, broadly ovate to broadly elliptic, green to green-brown, apex round or sometimes weakly shouldered; style 0.15-0.3 mm long, cylindrical; stigma 0.2-0.4 mm diam. Nectaries 4, 0.2-0.3 × 0.1-0.15 mm, oblong to oblong-triangular, green. Silicles cartilaginous when fresh, coriaceous when dry, 3.0-3.7 × 2.6-3.1 mm, orbicular to orbicular-rhomboid, apex obtuse to shallowly notched, valves pale brown,glabrous, not winged; style 0.2-0.3 mm long, exserted. Seeds 1.6-1.7 × 0.9-1.1 mm, narrowly ovoid, brown to orange-brown, not winged. FL Dec-Mar. FR Jan-Jul.

Representative Specimens.

New Zealand (South Island): Oamaru, n.d., D. Petrie s.n., (WELT SP027632); Weston, North Otago, n.d., D. Petrie, s.n., (CHR 328313); south of Orore Point, North Otago, March 1982, T. R. Partridge s.n., (CHR 464024); Bridge Point, near Kakanui, North Otago, 13 February 1988, P. N. Johnson 751, (CHR 439956); Dunedin, February 1920, A. Wall s.n., (CHR 329217); Dunedin, St Leonards, 31 December 1896, B. C. Aston s.n., (WELT SP027641, SP027642); near Port Chalmers, Deborah Bay, March 1891, D. Petrie s.n., (WELT SP027633); Aramoana, The Mole, 13 November 1997, P. J. de Lange 3378 & J. W. Barkla, (AK 234312); Sandymount, Otago Peninsula, 12 May 1985, P. N. Johnson 300, (CHR 417850); Tairoa Head, Otago Peninsula, 27 March 1998, J. Barkla s.n. & L. Perriman, (CHR 579981); near mouth of Catlins River, n.d., D. Petrie s.n., (WELT SP 027639); The Nuggets, South Otago, 5 Apr 1984, J. Ward s.n., (CHR 415751). South Otago, Waikawa Harbour, North Head, 9 February 1896, B. C. Aston s.n., (WELT SP027640); The Mole, Aramoana, 13 July 2009, P. B. Heenan s.n., (CHR 609772); Bridge Point, Orore Point, Waianakaru Road, 12 July 2009, P. B.Heenan s.n., CHR 609774. Cultivated (New Zealand): Auckland Regional Botanic Gardens, ex. Dunedin, The Mole, 1 December 1996, J. Lord 5/96, (AK 231116); Landcare Research experimental nursery, Lincoln, ex Bridge Point, 10 July 2008, P. B. Heenan s.n., (CHR 609797); Landcare Research experimental nursery, Lincoln, ex Aramoana, 10 July 2008, P. B. Heenan s.n., (CHR 609800); Landcare Research experimental nursery, Lincoln, ex Wharekakahu Island, 10 July 2008, P. B. Heenan s.n., (CHR 609801); Landcare Research experimental nursery, Lincoln, ex Nugget Point, 30 March 2009, P. B. Heenan s.n., (CHR 609805); Landcare Research experimental nursery, Lincoln, ex Wharekakahu Island, 25 January 2010, P. B. Heenan s.n., (CHR 609814).

Distribution

( Fig. 15 ). Endemic. New Zealand, South Island, Otago and Southland. Lepidium crassum once ranged from the Waitaki Valley (an inland location) and coastal locations at Oamaru to North Head, Waikawa Harbour in the south Catlins. Today, Lepidium crassum is most common on Otago Peninsula, but occurs in small populations from near Kakanui, North Otago to The Nuggets, South Otago.

Recognition.

Lepidium crassum differs from the related Lepidium oleraceum by its usually much smaller stature ( Fig. 34 ) and seasonal growth habit (with plants dying back to a basal rosette overwinter). Lepidium crassum has distinctly petiolate, uniformly broadly elliptic, elliptic to obovate, thickly coriaceous, often doubly crenate leaves with obtuse to truncate apices ( Figs 35 , 36 ). Its silicles are usually orbicular, sometimes orbicular-rhomboid, and with obtuse to shallowly notched apices ( Fig. 37 ) and by its rDNA ETS sequence.

Ecology.

Known from scattered populations that usually comprise fewer than 50 plants in a small geographic area. Lepidium crassum usually occurs on coastal headlands and rocky outcrops where it grows in disturbed open areas and among coastal herbfield of Disphyma australe subsp. australe and Samolus repens (J.R.Forst. et G.Forst.) Pers. var. repens. This species has also colonised the man made ‘Mole’ at Aramoana ( Fig. 34 ) where it is can be common amongst rubble, concrete blocks and landfill.

Conservation Status.

Lepidium crassum is known from a small number of wild populations on the Otago coast. As most populations comprise few plants or occur on unstable coastal headlands and rocky outcrops, this species is vulnerable to stochastic events. We estimate there are between 250 and 1000 plants and the largest population comprises fewer than 300 plants. Using the New Zealand Threat Classification System ( Townsend et al. 2008), Lepidium crassum qualifies as 'Threatened/Nationally Endangered’ (criterion B(1/1). We recommend appending the qualifiers ‘CD’ (Conservation Dependent - because there have been several populations established by the Department of Conservation and these are being actively managed), ‘DP’ (Data Poor - to reflect uncertainty over plant numbers), ‘EF’ (Extreme Fluctuations - because the largest known monitored population, that on Wharekakahu Island, appears to naturally undergo huge and apparently natural population fluctuations (J. W. Barkla pers. comm.)), and ‘RR’ (Range Restricted - because it is naturally confined to a geographically small part of the New Zealand Botanical Region).

Figures

Figure 15. Distribution of Lepidium aegrum, Lepidium amissum, Lepidium castellanum (Kermadec Islands only), Lepidium banksii, and Lepidium crassum.

Figure 33. Holotype of Lepidium crassum Heenan et de Lange.

Figure 34. Wild plant of Lepidium crassum showing growth habit at Aramoana Mole.

Figure 35. Leafy stem of Lepidium crassum showing basal leaves.

Figure 36. (From left to right) basal-, mid- to upper-stem leaves of Lepidium crassum. Scale bar = 20 mm.

Figure 37. Mature silicle of Lepidium crassum. CHR 439956. Scale bar = 1 mm.