Lepidium amissum, 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 : 20-24

Lepidium amissum sp. nov.

A L. obtusato habitu suberecto parce ramoso et sine rhizome, caulibus arcutis potius quam flexuosis, foliis rosulae et caulis inferi profunde denticutis persistente oblanceolato-spathulatis ad obovato-spathulatis, foliis caulis superi sparsis lanceolatis ad anguste oblanceolatis vel obdetoideis truncatis et profunde dentatis (raro integris) paribus dentorum usque ad 6 profunde incises et sparsim foliaceis, racemis longioribus quibus non obscuris caulibus vegetativis siliclisque parvioribus et angustioribus differt.

Holotype.

New Zealand ( Fig. 16 ): Cliffs between Karekare and Manukau Heads, January 1917, T. F. Cheeseman s.n., AK 4474! Isotypes: AK 206570!, WELT SP030095!

Etymology.

The epithet ' amissum ' is derived from the Latin ' amissus ' meaning ‘lost’ and is used here to refer to the loss though extinction, of this plant from the New Zealand flora.

Description

( Figs 17 -20 ). Glabrous, suberect, sparingly branched, succulent, perennial, herb forming open patches up to c. 1 m diam. Rootstock stout, woody, exposed portion rough, covered in old dead stem and rosette-leaf remnants admixed with actively growing stems. Stems arching, widely spreading, possibly with apices weakly ascendent, succulent, mature stems woody, 200-300 × 3-6 mm, densely leafy near base, leaves more widely spaced along upper stems. Leaves glabrous, coriaceous, probably succulent, dark green, planar, variable size and shape. Rosette leaves persistent at fruiting 71.7-95.2 × 12.4-23.2 mm, oblanceolate-spathulate to obovate- spathulate; apex, truncate, praemorse, with 3-8 deeply incised teeth; margin coarsely and often irregularly incised or dentate, often weakly bidentate, with 24-36 pairs of teeth; teeth up to 4.8 mm deep, irregular in size, protruding beyond leaf outline; base narrowly attenuate to cuneate, ± decurrent, petiole distinct, 43.4-55.2 × 1.4-2.3 mm long, slightly winged, or not, channelled. Lower stem leaves similar to rosette leaves, apparently persistent, widely spaced, gradually decreasing in size toward inflorescence; petioles distinct, slightly winged or not. Upper stem leaves much reduced; lamina 10.3-27.5 × 3.4-7.6 mm, lanceolate, narrowly oblanceolate, lanceolate to narrowly obdeltoid, apex truncate, with 3-4 prominent teeth, margins prominently toothed in upper ⅓ of lamina with 4-6 deeply incised pairs of teeth (rarely entire except for apex), base cuneate to broadly cuneate; petiole distinct or indistinct, up to 6 mm long when present, channelled. Inflorescence racemose, terminal and lateral, conspicuous, sparingly leafy and unfettered by associated vegetative leafy stems; racemes 22-68 mm long, rachis 0.9-1.6 mm diam., glabrous; pedicels 2.8-3.2 mm long at flowering, erecto-patent, elongating somewhat after anthesis, glabrous. Flowers 4.3-4.6 mm diam. Sepals 4, saccate, overlapping at base, green, apex obtuse, margin white, shape and size dimorphic; lateral sepals 2.2-2.9 × 2.1-3.0 mm, suborbicular, mostly glabrous, sometimes sparsely hairy, hairs 0.2-0.4 mm long, caducous; median sepals 1.9-2.9 × 1.5-1.7 mm, broadly elliptic to obovate, abaxial surface glabrescent, sparsely hairy, hairs 0.2-0.4 mm long, caducous. Petals white, 1.3-1.8 × 1.3-1.8 mm, erect, claw minute, 0.2-0.3 mm; limb orbicular, apex obtuse. Stamens 4, ± equal lengths, 1.2-1.8 mm long, base 0.6-1.0 mm wide; anthers 0.6-0.8 mm long, yellow, pollen yellow. Ovary 1.3-1.8 × 1.3-1.7 mm, broadly ovate to suborbicular green, apex distinctly notched; style 0.3-0.5 mm long, cylindrical below, spreading at apex; stigma 0.5-0.6 mm diam. Nectaries 4, green, 0.12-0.14 × c. 0.09 mm, narrow oblong, apex obtuse. Silicles 3.4-4.5 × 2.9-3.9 mm, broadly ovate, oval to obovate, apex prominently notched, valves yellow-green (in dried specimens), glabrous, slightly winged; style 0.2-0.5 mm long, not or only slightly exserted. Seeds 2.0-2.7 × 1.8-2.0 mm, obovate, broadly obovate, brown to orange-brown, not winged. FL: Dec-Jan. FR: Dec-Jan.

Representative Specimen.

New Zealand (North Island): North Auckland, Cliffs north of the Manukau heads, December 1870, T. F. Cheeseman s.n., (AK 4473).

Distribution

( Fig. 15 ). Endemic. New Zealand, North Island, where it was recorded from 'between Manukau Heads and Karekare’ ( Cheeseman 1906, 1925), not the ‘Titirangi’ noted by Kirk (1899). Lepidium amissum was last collected from the west Auckland coastline in 1917 and is presumed to be extinct.

Recognition.

Lepidium amissum had previously been included in Lepidium obtusatum , perhaps because the species have no obvious floral differences and both have deeply notched and winged silicles with tapering bases. However, from Lepidium obtusatum , Lepidium amissum differs by the non-rhizomatous, suberect growth habit; arching, sparingly leafy stems ( Fig. 16 ); long persistent, deeply, and sharply incised rosette and lower stem leaves ( Figs 17 , 18 ); upper stem leaves which are lanceolate, narrowly oblanceolate, to narrowly obdeltoid and mostly prominently toothed, with up to 6 pairs of deeply incised teeth, and with a truncate apex bearing 3-4 prominent teeth. The inflorescences of Lepidium amissum are larger, only sparsely leafy when mature, and without associated vegetative stems ( Fig. 19 ). The silicles are smaller than those of Lepidium obtusatum ( Fig. 20 ).

Ecology.

Little is known about the habitat preferences and ecology of Lepidium amissum , beyond that it grew on sea cliffs ( Cheeseman 1906, 1925).

Conservation Status.

Lepidium amissum is considered to be extinct. There have been repeated unsuccessful surveys for this species over the last fifty years by various botanists. Aside from the type the species is known from only one collection made in 1917. This collection and the type came from an ill defined area of coastline stretching for some 6 km from the Manukau Heads to Karekare. Today this coastline is protected within the Centennial Park, Waitakere Ranges. However, during the period when this species was gathered, all of the coastline was being modified as a result of kauri ( Agathis australis (D.Don) Lindl.) logging (see Harvey 2001, 2006; MacDonald and Kerr 2009), and this may have contributed to its eventual extirpation. It does seem that Lepidium amissum was already uncommon at the time of its discovery and it is possible that the gatherings made by Thomas Cheeseman where sufficient to cause its extinction as they are copious and comprise many stems.

Figures

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

Figure 16. Holotype of Lepidium amissum de Lange et Heenan.

Figure 17. Basal stem leaves of Lepidium amissum. AK 4473

Figure 18. Basal stem leaf of Lepidium amissum. AK 4473.

Figure 19. Upper-stem leaves and inflorescences of Lepidium amissum. AK 4473.

Figure 20. Mature silicle of Lepidium amissum. AK 4473. Scale bar = 1 mm.