Lepidium aegrum, 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 : 15-20

Lepidium aegrum sp. nov.

A L. oleraceo caulibus gracilibus flexilibus, foliis pallide viridibus membranaceis, lanceolatis elliptico-lanceolatis vel anguste ellipticis, apice prominente acuto vel subacuto, marginibus serratis dentibus prominentibus profundis, et sequentia nucleotidorum DNA distinguenda.

Holotype

( Fig. 9 ). New Zealand: Canterbury, Lincoln, Landcare Research experimental nursery, ex Banks Peninsula, rock stack near Island Bay, May 2011, P. B. Heenan s.n., CHR 616211!

Etymology.

The specific epithet ' aegrum ' is derived from Latin, meaning 'diseased and/or sick body’ and refers to the condition of the plants in the single known extant wild population on the unnamed rock stack near Island Bay, many of which are infected with turnip mosiac virus ( Fletcher et al. 2009).

Description

( Figs 10 -14 ). Tap-rooted, strongly pungent smelling, perennial herb. Growth habit open, up to 50 cm tall, stems arising from basal woody stems. Stems upright, slender, flexible; mature stems woody, 100-500 × 10-12 mm, often devoid of foliage on middle and lower parts of stems; new stems 80-200 × 3-4 mm, leafy, glabrous. Leaves glabrous, membranous, light green, planar, pellucid glands sometimes scattered on abaxial surface, rosette and stem leaves usually withering, variable in size and shape. Leaves of young and vigorous plants and stems: lamina 35-80 × 10-20 mm, lanceolate, elliptic-lanceolate, narrowly elliptic; apex subacute, with a single prominent tooth; margin singly serrate, with 8-12 pairs of teeth; teeth up to 3.5 mm deep, not overlapping; base attenuate, tapering to distinct petiole. Leaves of mature plants and cauline stems: lamina 30-65 × 4-11 mm, narrowly lanceolate, elliptic-lanceolate, narrowly elliptic; apex acute to subacute, with a single prominent tooth; margin singly serrate in upper and/or lower half, with 2-10 pairs of teeth; teeth up to 1.2 mm deep, not overlapping; base attenuate, tapering to petiole. Inflorescence terminal and lateral, racemose, often branched, up to 95 mm long, rachis up to 2.1 mm diam., glabrous; pedicels 4-10 mm long, erecto-patent, glabrous. Flowers 4.0-4.5 mm diam. Sepals 4, 1.0-1.5 mm long, saccate, green, apex obtuse, margin white, shape dimorphic; lateral sepals broad, 1.0-1.1 mm diam., orbicular, abaxial surface often hairy, hairs entirely eglandular or with glandular tip, 0.2-0.3 mm long; median sepals narrow, 0.8-0.9 mm diam., broadly elliptic, glabrous. Petals white, 2.3-2.5 × 1.2-1.4 mm, spreading, claw 0.7-0.9 mm long; limb broadly elliptic to orbicular, apex obtuse to rounded. Stamens 4; filaments 1.7-2.0 mm long, base 0.3-0.4 mm diam., equal; anthers 0.4-0.5 mm long. Ovary 0.9-1.0 × 0.9-1.0 mm, broadly ovate to broadly elliptic, green, apex usually with shoulders; style 0.3-0.4 mm long, cylindrical; stigma 0.3-0.4 mm diam. Nectaries 4, 0.2-0.3 × c. 0.1 mm, oblong, green. Silicles cartilaginous when fresh, coriaceous when dry, 4.0-4.7 × 3.2-3.5 mm, elliptic-rhomboid to orbicular-rhomboid, apex shallowly notched, valves pale brown,glabrous, not winged; style 0.3-0.4 mm long, exserted. Seeds 1.6-1.7 × 0.9-1.0 mm, narrowly ovoid, brown to orange-brown, not winged. FL Mar. FR Mar.

Representative Specimens.

New Zealand (South Island): Banks Peninsula, Waikerikeri, n.d., R. M. Laing s.n., (AK 4463); Banks Peninsula, Akaroa, Akaroa Head, Island Bay, Unnamed Islet, July 2002, N. Head s.n., AK 283510. Cultivated (New Zealand): Landcare Research experimental nursery, Lincoln, ex Akaroa, Akaroa Head, Island Bay, Unnamed Islet, 5 September 2008, P. J. de Lange 7363 & G. Houliston, (AK 303515);Landcare Research experimental nursery, Lincoln, ex Island Bay, Banks Peninsula, 13 January 2010, P. B. Heenan s.n., (CHR 609820); Landcare Research experimental nursery, Lincoln, ex Island Bay, Banks Peninsula, 13 January 2010, P. B. Heenan s.n., (CHR 609821); Landcare Research experimental nursery, Lincoln, ex Island Bay, Banks Peninsula, 1 April 2009, P. B. Heenan s.n., (CHR 609804); Landcare Research experimental nursery, Lincoln, ex Island Bay, Banks Peninsula, 11 August 2009, P. B. Heenan s.n., (CHR 609792).

Distribution ( Fig. 15 ). Endemic. New Zealand, South Island, Canterbury, Banks Peninsula, Island Bay, unnamed rock stack.

Ecology.

Known from a single wild population on a small and unnamed island near Island Bay. Here it grows in open and disturbed areas among petrel burrows and Disphyma australe (W.I.Aiton) N.E.Br. subsp. australe ( Fig. 6 ). Additional populations of Lepidium aegrum have been established in Canterbury on Motunau Island (Pegasus Bay), Quail Island (Lyttleton Harbour), and at Stony Bay (Banks Peninsula).

Recognition. Lepidium aegrum is distinguished by its slender flexible stems ( Figs 11 , 12 ), light green membranous leaves that are lanceolate, elliptic-lanceolate or narrowly elliptic with a prominent acute to subacute apex, and margins that are serrate with prominent and deep teeth ( Fig. 13 ).

Conservation Status. Lepidium aegrum is known from a single wild population and three additional populations that have been established with nursery-raised plants. The single wild population and unknown recruitment patterns means that this species is especially vulnerable to stochastic events. Furthermore, turnip mosiac virus, which deforms and retards growth, is common in plants at the wild population, and this will likely reduce reproductive success ( Fletcher et al. 2009). Using the New Zealand Threat Classification System ( Townsend et al. 2008), Lepidium aegrum qualifies as Threatened/Nationally Critical. We recommend appending the qualifiers ‘CD’ (Conservation Dependent - as it has been established and is being managed at Motunau and Quail islands, and at Stony Bay), ‘DP’ (Data Poor - to reflect uncertainty over plant numbers and population trends), ‘OL’ (One location - since it is known from a single wild population).

Figures

Figure 6. Cauline leaves of (A) Lepidium oligodontum - variation within a single plant, (B) Lepidium oligodontum - variation amongst plants from different locations: (left to right) The Sisters, Western Reef, Point Somes, Moriori Creek, Star Keys, Rangatira Island, Antipodes Island. (C) Lepidium panniforme, (D) Lepidium rekohuense. Scale bars = 20 mm.

Figure 9. Holotype of Lepidium aegrum Heenan et de Lange.

Figure 10. Lepidium aegrum plant in the wild showing usual growth habit (Lepidium aegrum growing in association with Disphyma australe subsp. australe) amongst petrel burrows).

Figure 11. Lepidium aegrum stem showing four inflorescences. Scale bar = 20 mm.

Figure 12. Lepidium aegrum leafy stems showing mid-stem and apical foliage. Scale bar = 20 mm.

Figure 13. Lepidium aegrum (from left to right) basal- to mid-stem foliage. Scale bar = 20 mm.

Figure 14. Mature silicle of Lepidium aegrum. CHR 222380. Scale bar = 1 mm.

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