Lepidium oleraceum G.Forst. ex Sparrm., Nova Acta Soc. Sc. Upsal. iii, 193 (1780)

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 : 71-84

Lepidium oleraceum G.Forst. ex Sparrm., Nova Acta Soc. Sc. Upsal. iii, 193 (1780)

Type Collection:

From cultivated plants, originally collected from New Zealand (see below).

Neotype

( Fig. 69 , designated here): S, Sparrman, Nova Zelandia.

Notes:

Nicolson and Fosberg (2004) were unsure about typification of Lepidium oleraceum G.Forst. ex Sparrm., and the name has not been typified. They listed two Spar rman specimens at S, but did not select a type specimen since neither of these appeared to have been gathered from cultivated plants. Given the revised taxonomic treatment presented here for the Lepidium oleraceum complex, it is necessary to be certain of the application of Lepidium oleraceum G.Forst. ex Sparrm. Therefore, we select one of the Sparrman sheets as neotype.

When describing Lepidium oleraceum , Sparrman (1780) indicated that the description was based on cultivated plants: ' Prima vero, quam heic ex Forsterianis offerre licet, in praedi patrimoniali Sponga, seminibus ex Nova Zelandia allatis, culta per maximam partem aestatis floruit, Forsteroque Lepidium Oleraceum dicta, quippe qua, cum oleo & aceto, oleraceorum loco, ut & in jusculo cocta, deficientibus alius generis vegetabilibus, in itinere utebamur '. Indeed, Lepidium oleraceum was cultivated in Upsala (Sweden), where Sparrman resided, as it is one of 11 species of Lepidium listed by Thunberg (1803) as having been grown there between 1780 and 1800.

It is unusual that this description was based on cultivated plants since it was the practice of A. Sparrman and G. Forster to prepare descriptions from freshly collected material during Captain Cook’s second voyage ( Forster and Forster 1776 (see Edgar (1969) for translation). Plant material of Lepidium oleraceum , along with other edible, herbaceous coastal plants was frequently collected during the New Zealand part of the voyage to be utilised for their antiscorbutic properties ( de Lange and Norton 1996). Therefore, there would have been ample opportunity to prepare the description from freshly collected material. Indeed, as noted by Nicolson and Fosberg (2004), the published description of the later homonym Lepidium oleraceum G.Forst. differs from that of Lepidium oleraceum G. Forst. ex Sparrm., and it is most likely that the description of the homonym was prepared on the voyage from fresh material.

The wild locality of the neotype of Lepidium oleraceum is not known, except that it is from New Zealand. While anchored in Queen Charlotte Sound during May 1773, G. Forster noted 'the antiscorbutic plants grew on every beach’ and 'we immediately gathered vast quantities... of a well-tasted scurvy-grass ( Lepidium )' ( Forster 1777, p. 126). They also collected it from Long Island ( Hoare 1982, vol. II, p. 287), and saw it in the vicinity of Maori settlements: 'near all the places where the Indians have their huts, there grows a kind of Scurvy-Grass or Lepidium ' ( Hoare 1982, II, p. 297). Therefore, since J. R. Forster, G. Forster, and A. Sparrman would have had ample opportunity to collect Lepidium oleraceum in Queen Charlotte Sound it is very likely that the neotype was collected from there. Dusky Sound, Fiordland, is the only other location where landfall was made in New Zealand during Cooks 1773 voyage, but the species is not known from the Fiordland coastline so is unlikely to have been collected from there.

Etymology.

The exact meaning of the species ' oleraceum ' was not given by Sparrman (1780). However the epithet derives from the Latin ' oleraceus 'meaning 'used for herbs or vegetables’ ( Taylor 2002), a point that Sparrman had alluded to in a brief note he wrote in Latin on the backside of the neotype sheet.

= Lepidium oleraceum var. acutidentatum Kirk, Stud. Fl. N.Z., 35 (1899)

Type Collection:

'NORTH and SOUTH Islands; STEWART Island; the SNARES; AUCKLAND Islands; CHATHAM Islands. In places near the sea.'

Neotype

( Fig. 70 , designated here): T. Kirk 367, March 1869, Taranga Islands - labelled as 'Lepidium oleraceum var. incisum’ in Kirk’s hand. WELT SP027646!

Notes:

Kirk (1899) described var. acutidentatum thus 'stems with slender leafy branches. Leaves 1in.- 1½ in. long, narrow, cuneate or oblong-spathulate, the upper portion acutely serrate or almost dentate’. Plants matching this vague description span large parts of the range of Lepidium oleraceum s.l. Our searches of the herbaria where Kirk traditionally lodged specimens (see comments by de Lange 2007) have failed to find any specimens labelled by Kirk as var. acutidentatum. However, there are a range of specimens in WELT (WELT SP027646!, SP027647!, SP027648!, SP030087!) bearing in Kirk’s hand the manuscript names 'var. erectum’ and 'var. incisum’, which, being unpublished, have no nomenclatural status whatsoever. These specimens, along with the generally confusing notes provided by Kirk (1899, p. 34-35) in his entry for Lepidium oleraceum , suggest that Lepidium was a genus he was still working on close to his death on 8 March 1898 ( Moore 1973, but see also comments by de Lange 2007 and de Lange and Gardner 2002). At the time of his death, Kirk was using these manuscript names on his herbarium specimens, but he was either undecided on his final choice of epithet or had yet to relabel his specimens as var. acutidentatum, a name which was then later published posthumously when his unfinished Flora manuscript was uplifted and published ( Kirk 1899). Despite this confusion, Kirk’s description of var. acutidentatum matches most closely those WELT specimens (T. Kirk 367, WELT SP027646, T. Kirk 368, WELT SP027647) that he had collected from Taranga Island, which is the largest of the Hen and Chicken Islands group and labelled 'var. incisum’. Notably, both specimens match his protologue as to the description of var. acutidentatum, e.g., 'slender leafy branches... Leaves 1in.- 1½ in. long, narrow, cuneate … upper portion acutely serrate’. Therefore, in the absence of any suitable material for a lectotype we designate T. Kirk 367 (WELT SP027646) as the neotype of Lepidium oleraceum var. acutidentatum Kirk.

Etymology.

The meaning of the epithet ' acutidentatum ' was not given by Kirk (1899). However, the epithet as indicated by the protologue probably derives from the sharply toothed leaves.

= Lepidium oleraceum var. frondosum Kirk, Stud. Fl. N.Z., 34 (1899)

Type Collection:

'Banks and Sol., MSS and Ic.'

Lectotype

( Fig. 71 , designated here): WELT SP063976/A! IsolectotypeWELT SP063976/B!

Notes:

Kirk (1899, p. 34) despite his rather confused and evidently incomplete treatment of Lepidium oleraceum nevertheless clearly described Lepidium oleraceum var. frondosum in the following manner: 'var. frondosum, (sp.), Banks and Sol. MSS. and Ic. Robust, leaves large, fleshy, broadly cuneate-oblong or oblong, sometimes 3in-5in. long and 1in. wide, sessile or narrowed into a broad petiole, serrate’. Although no specimens or locations were cited by Kirk in his protologue, his wording makes it clear that any specimens collected by Banks and Solander and labelled by them 'Lepidium frondosum’ and any accompanying illustrations made from these specimens constituted the type collections from which he formally recognised his Lepidium oleraceum var. frondosum. Therefore, we have selected WELT SP063976/A as lectotype because this sheet, comprising two flowering and fruiting, leafy specimens, is labelled both by Kirk ' Lepidium oleraceum Forster Prodr. N. 248 var. frondosum ' and also in Solander’s hand as 'Lepidium frondosum Mscr’.

Etymology.

The meaning of the epithet ' frondosum was not given by Kirk (1899) who took the name from the unpublished Banks and Solander manuscript. Nevertheless it seems reasonable to assume that the epithet refers to the large, much tooth, arched leaves typical of the robust forms of Lepidium oleraceum that Kirk referred to this variety.

= Lepidium oleraceum var. serrulatum Thell., Die Gatt. Lepidium, 293, (1906)

Holotype

( Fig. 1 ): P! ' Lepidium oleraceum Forst. var. serrulatum Thell. n. var. 1905 3 VIII, New River, Godey’ (label in A. Thellung’s hand).

Notes:

Thellung (1906, p. 293) described Lepidium oleraceum var. serrulatum from a single undated gathering which, according to the specimen details, came from 'New River’ where it was collected by Godey. Allan (1961, p. 177) equated this location thus: 'S[outh Island]. New River estuary, Riverton, Southland’. The holotype bears two labels, one written in the hand of the naming author, Thellung, and the other in an unknown hand, presumably Godey, which reads ' Lepidium oleraceum Forst var. New River, Nouv. Zélande, Godey’. We have been unable to find out who the collector Godey was.

Thellung distinguished his new variety from Lepidium oleraceum s.s. thus: ' folia obovata, a medio ad apicem regulariter subtiliter et acute serrator ' meaning 'foliage obovate, regularly and acutely, finely serrated from middle of the leaf to the apex’.

Significantly the silicles of the holotype are acute rather than notched, a condition seen only in Lepidium castellanum and Lepidium oleraceum , neither of which are known from the southern South Island. For this reason, we suspect that the gathering was collected from the northern part of New Zealand, rather than the southern South Island, and that Allan’s interpretation of location of 'New River’ is incorrect. We also suspect that the exact location of the 'New River’ will now never be known. In all probability this name may have simply been one used locally for some other part of New Zealand.

The obovate leaves of Lepidium oleraceum var. serrulatum place this variety within Lepidium oleraceum (as treated here) rather than Lepidium castellanum . Within Lepidium oleraceum s.s., there are a few vegetatively similar, obovate-leaved plants with finely serrated leaf margins that approach the extreme condition seen in var. serrulatum. These gatherings all come from offshore islands in the northern part of the North Island (e.g., Three Kings Group, A. E. Wright 6072,AK 173005; Rock Stack north of Motuopao Island, R. Parrish s.n., AK 196229; Motutakapu Island, R. Parrish s.n., AK 209112). However none of those obovate-leaved plants have such prominently serrated leaf margins as the holotype of var. serrulatum. Based on these observations, we think that var. serrulatum was collected from somewhere in the northern part of the range of Lepidium oleraceum , and that it represents nothing more than an extreme form of that species, which even following our treatment here remains a highly variable species.

Etymology.

Thellung (1906) chose the epithet ' serrulatum ' to reflect the finely serrated / serrulate leaves of the holotype.

Description

( Figs 72 -75 ). Tap-rooted, glabrous, strongly pungent smelling, much-branched, erect, perennial, herb up to 1.2 × 1.3 m, usually less. Rootstock woody, exposed portion smooth, in old specimens usually retaining dead stem remnants admixed with actively growing stems. Stems sparse to closely packed depending on local growing conditions, persistent (only partially dying back in winter), erect to spreading; mature stems 0.2-1.5 m long, 3-15 mm diam. stout, woody near base, weakly angled to terete, devoid of foliage on lower and middle parts of stems; new stems 20.0-800.0 × 2.5-10.0 mm, fleshy, rigid, initially ± square, prominently angled, becoming ± terete with age, bases much covered in leaf abscission scars, middle and upper portion leafy. Leaves coriaceous, fleshy, green to dark green, rosette-leaves absent, stem leaves withering with age, variable in size and shape; petiole distinct, 2.0-50.0 × 1.2-5.3 mm, decurrent, weakly to prominently channelled, sometimes broadly winged, often with a broadly sheathing base; lamina variable 16.2-120.0 × 3.0-46.3 mm decreasing in size toward inflorescences, linear, linear-lanceolate, lanceolate, obovate, oblong, obdeltoid, oblanceolate to broadly elliptic, rarely spathulate; apex acute, subacute to obtuse, usually tridentate, rarely praemorse; margin coarsely and regularly to irregularly dentate, dentate to biserrate, sometimes deeply incised, finely denticulate or subentire; teeth usually protruding beyond leaf outline; in 10-60 pairs, up to 4 mm deep, increasing in size toward apex, sometimes with sporadic larger teeth randomly appearing from about the middle portion of lamina margin, or with teeth arranged ± evenly along lamina margin; base broadly cuneate tapering, sometimes extending into a broad petiole wing. Inflorescences racemose, 20.4-90.5 mm long at fruiting, rachis 0.7-2.35 mm diam., terminal and lateral, usually leaf-opposed, often long-persistent, pedicels 3-10 mm long at fruiting, erecto-patent. Flowers 3.0-4.2 mm diam., fragrant. Sepals 4, saccate, pale to dark green with a broad white, ± undulose margin; lateral sepals broad, 0.5 -1.4 mm diam., orbicular, obovate to broadly obovate, ± overlapping at base, apex rounded to obtuse, abaxial surface often hairy, hairs 0.1-0.4 mm long, eglandular or with glandular tip, mostly shedding at anthesis except near base, median sepals 0.5-0.9 mm diam., broadly elliptic, pale to dark green with a broad white, ± undulose margin, apex rounded to obtuse, abaxial surface glabrous. Petals white, 1.3-2.2 × 1.6-2.3 mm, spreading, claw 0.4-0.9 mm long; limb obovate, obovate-spathulate to orbicular, apex obtuse to rounded often slightly emarginate, margins smooth, sometimes weakly undulose. Stamens 4, filaments 1.2-2.0 mm long, white; anthers 0.3-0.5 mm long, yellow. Ovary 1.1-1.8 × 0.6-1.3 mm, ovate, broadly ovate to elliptic, green-brown, apex round or subacute; style 0.11-0.4 mm long, cylindrical; stigma 0.2-0.5 mm diam. Nectaries 4, 0.2-0.3 × 0.1-0.15 mm, narrow-oblong to deltoid, pale translucent green. Silicles cartilaginous when fresh, coriaceous when dry, 2.6-4.8 × 1.7-3.4 mm, elliptic, rhomboid (rarely orbicular-rhomboid), apex acute to rounded, valves green maturing grey-green to straw-yellow, glabrous, not winged; style 0.3-0.6 mm long, exserted. Seeds 2, 1.2-1.9 × 0.8-1.4 mm, narrowly to broadly ovoid, brown to orange-brown, not winged. FL Aug-Jun. FR Sep-Jul.

Representative Specimens.

Kermadec Islands: Herald Islets, Dayrell Island, 17 May 2011, P. J. de Lange K911, (AK 326657); Herald Islets, Napier Island, 18 May 2011, P. J. de Lange K894, (AK 326586);Curtis Island, n.d., R. E. A. Shakespear s.n., (AK 4465); Curtis Island, November 1900, F. Shakespear s.n., (AK 128467); 18 July 1969, Curtis Island, W. R. Sykes 842/K, (CHR 193786); Curtis Island, 18 July 1969, W. R. Sykes 843/K, (CHR 193787); L’Esperance Rock, 26 May 2011, P. J. de Lange K859, (AK 326039). New Zealand (Three Kings Islands). Three Kings, November 1889, T. F. Cheeseman s.n., (AK 4466);Great Island (Manawa Tawhi), 1 January 1948, G. T. S. Baylis s.n., (AK 24128); South-West Island, 10 January 1950, G. T. S. Baylis s.n., (OTA 3804); Hole in the Wall Rock, 1 December 1983, A. E. Wright 6072, (AK 173005);Hinemoa Rock, 30 November 1983, A. E. Wright 6062, (AK 172998); Arbutus Rock, 1 December 1983, A. E. Wright 6074, (AK 173007);West Island, 29 November 1983, A. E. Wright 6060, (AK 172996). New Zealand (North Island). Motuopao Island, 11 May 1994, L. J. Forester s.n., (AK 294641); Matapia Island, 21 May 1993, L. J. Forester s.n., (AK 212201); Poor Knights Islands, Tawhiti Rahi, Hope Point, 26 April 1991, A. E. Wright 11492, (AK 201743); Poor Knights Islands, Aorangi Island, Crater Bay, 13 January 1978, G. N. Park s.n., (CHR 385039, WELT SP077730); Poor Knights Island, Tunnel Island (Aorangaia), 17 November 1933, L. B. Moore s.n. & L. M. Cranwell, (AK 100093); Mokohinau Islands, Stack “H”, 10 November 1993, P. J. de Lange 2643, (AK 226975, CANU, CHR, WAIK); Mokohinau Islands, Maori Bay Island (Hokoromea), 2 January 1984, E. K. Cameron 2664, (AK 273235); Mokohinau Island, Knights Group, Stack “D”, 13 November 1993, P. J. de Lange 2620, (AK 226964, CHR); Mokohinau Islands, Motuharakeke Island, 15 November 1993, P. J. de Lange 2662, (AK 226984 CHR, WAIK); Mokohinau Islands, Fanal Island (Motukino), 22 May 1979, A. E. Wright 3152, (AK 150595 WELT SP077068); Hen & Chicken Islands, Hen Island (Taranga), May 1880, T. F. Cheeseman s.n., (AK 4469); Little Barrier Island, December 1898, T. F. Cheeseman s.n., (AK 4470); Little Barrier Island, West Landing, 6 Oct 1945, B. Molesworth s.n., (AK 100091); Great Barrier Island (Aotea Island), Grey’s Archipelago, January 1868, T. Kirk s.n., (AK 11428, WELT); Great Barrier Island (Aotea Island), Broken (Pig) Islands, Mahuki Island, 2 January 1985, A. E. Wright 6883, (AK 171283); Oaia I, October 1953, Mr [sic] Wightman s..n., (AK 37510). Cuvier Island (Repanga), October 1895, T. F. Cheeseman s.n., (AK 4467, AK 221114, AK 221115, AK 247259); Mercury Island, Middle Island, 15 November 1983, E. K. Cameron 2536, (AK 272908); Mercury Bay, Motukorure (Centre Island), 5 March 1989, G. A. Taylor s.n., (AK 229759); Alderman Islands, Hongiora, May 1972, D. J. Court s.n. & A. Hardacre, (AK 131204); Motukaramarama Island, 30 August 1983, A. E. Wright5800, (AK 167081, CHR); South Auckland, Ngatutura Point, Shag Rock, 3 September 1988, P. J. de Lange 53, (CHR 462622);South Auckland, Albatross Point, Waioioi Reef, 15 September 2006, A. M. Brandon s.n. & D. W. Smith, (AK 297502); Bay of Plenty, Karewa Island, 26 April 2007, P. B. Cashmore s.n., S. J. Crump & J. Heaphy, (AK 299140); Bay of Plenty, Mt Maunganui, 1942, M. E. Sexton s.n., (AK 249218); East Cape Island (Whangaokeno), n.d.,L. Cockayne 9214, (AK 100089); East Cape, Waihau Bay, Gable-end Foreland, n.d., Hill s.n., (WELT SP023196). Taranaki, Sugar Loaf Islands, Motumahunga (Saddleback I.), 24 January 1989, G. A. S. Taylor s.n., (AK 295695); Hawke’s Bay, Cape Kidnappers, Black Reef, 19 November 1933, W. R. B. Oliver s.n., (WELT SP027655); Porirua, Mana Island, 1916, B. C. Aston s.n., (WELT SP027653); Porirua, Titahi Bay, n.d., B. C. Aston s.n., (WELT SP027652);South Wellington Coast, Cape Terawhiti, November 1908, B. C. Aston s.n., (AK 4468, AK 221113, WELT SP027657); South Wellington Coast, Mouth of the Karori Stream, 1 March 1931, W. R. B. Oliver s.n., (WELT SP027656); South Wellington Coast, Tongue Point, n.d., W. R. B. Oliver s.n., (WELT SP09712), Wellington, Seatoun, 28 February 1937, W. R. B. Oliver s.n., (WELT SP09711). New Zealand (South Island) Wharariki Beach, Archway Islands, Richard Seddon Island, 10 Febraury 2003, S. Courtney s.n., (CHR 551339); Wharariki Beach, north Nguroa Island, 10 February 2003, S. Courtney s.n., (CHR 551338). Marlborough, Pelorus Sound, Duffers Reef, 23 May 2001, S. Courtney s.n., (CHR 552377); Marlborough, Pelorus Sound, Bird Island, 21 May 2001, S. Courtney s.n., (CHR 552381); Marlbor ough, Titi Island, 27 January 1981, G. Y. Walls s.n., (CHR 416807); Marlborough, Stephens Island, 13 May 1957, M. E. Gillham s.n., (CHR 111512); Marlborough, Chetwode Islands, The Haystack, 29 March 1984, A. E. Wright 6435, (AK 174701); Marlborough, Chetwode Islands, Nukuwaiata Island, 29 March 1984, A. E. Wright 6450, (AK 174716); Marlborough, Chetwode Island, Sentinel Rock, 26 March 1984, A. E. Wright 6347, (AK 174639); Northern Brother Island, June 1963, G. Collett s.n., (CHR 141950); Queen Charlotte Sound, n.d.,J. H. Macmahon s.n., (AK 4471). Chatham Islands. Mangere Island, Mangere Island Nature Reserve, 14 February 2006, P. J. de Lange CH564 & P. B. Heenan, (AK 295979). Cultivated (New Zealand): Lincoln, ex Ngatutura Point, Landcare Research experimental nursery, 26 January 2010, P. B. Heenan s.n., CHR 609811.

Distribution

( Fig. 76 ). Endemic. Kermadec Island (Dayrell, Napier and Curtis islands). New Zealand, Three Kings, North, South (North-west Nelson and Marlborough Sounds and Chatham (Mangere Island) islands.

Recognition.

Although extremely variable with respect to stature, leaf shape, size and dentition, Lepidium oleraceum is consistently recognised by the glabrous pedicels and by the mature silicles which are elliptic, rhomboid (very rarely orbicular-rhomboid) and with an acute to rounded apex that leaves the style remnant standing proud above the silicle apex ( Fig. 75 ). Silicles often give the false impression of being notched, something that happens when the valves are over mature and so have started to dehisce at the apex. Lepidium oleraceum often forms a widely spreading but erect bushy plant whose stems are long persistent and, while slowing in growth over winter, do not die back to the rootstock as do all other New Zealand members of Lepidium oleraceum complex except Lepidium castellanum and, on occasion, Lepidium oblitum and Lepidium panniforme . Lepidium oleraceum also lacks the distinct rosette leaves seen in all other members of the Lepidium oleraceum complex except Lepidium castellanum .

Ecology.

Much has been written about the ecology of Lepidium oleraceum , of which the summary provided by Norton et al. (1997) still applies despite our segregation here of 10 new species from it. Lepidium oleraceum is intimately associated with sea-bird trails, roosts and nesting grounds. Plants are dependent on these birds not only for the habitats they create through disturbance but also the nutrients they bring from the sea in the form of guano and discarded or regurgitated food, and because these birds assist with seed dispersal. Seed dispersal is most readily facilitated by birds because Lepidium oleraceum , as well as growing around bird nests and burrows, is often used for nesting material. In this way, the seeds, which are mucilaginous when wetted, can easily stick to the feathers and feet of birds.

Lepidium oleraceum tends to be short-lived, with individual plants rarely persisting for more than three years in the wild and up to five in cultivation. It has also been observed that some wild populations are prone to sudden crashes, and may even completely die out, only to reappear some years later. It is unknown whether the reappearance is from a residual seed bank or from seeds dispersed by birds from another site. Plants may even behave as annuals in some locations because, despite its predilection for open, drought-prone coastal habitats, Lepidium oleraceum does not relish drought.

Norton et al. (1997) stressed the importance of sea birds in providing the nutrient regime necessary to sustain the species, arguing that the loss of sea bird breeding grounds from large parts of the country best explains the rapid demise of Lepidium oleraceum . However, while that view is probably still valid, some anomalies remain to be explained. For example, Lepidium oleraceum appears to have always been scarce on the Three Kings Islands, which are naturally predator-free and harbour large sea bird breeding colonies. On those islands, Lepidium is confined to white-fronted tern ( Sterna striata Gmelin, 1789) and red-billed gull ( Chroicocephalus scopulinus (Forster, 1844)) nesting grounds, and is absent from all other sea bird colonies, including the heavily burrowed ground left by breeding black-winged petrel ( Pterodroma nigripennis Rothschild, 1893). This requires further study, as on many Hauraki Gulf islands Lepidium oleraceum is usually absent from tern and gull nesting sites, and more usually associated with petrels such as grey-faced ( Pterodroma macroptera gouldi (F.W.Hutton, 1869)), black-winged, and Pycroft’s ( Pterodroma pycrofti Falla, 1933), or with shearwaters ( Puffinus spp.), white-faced storm petrels ( Pelagodroma marina Latham, 1790) and common diving petrels ( Pelecanoides urinatrix (Gmelin, 1789)). On some islands supporting these birds and gannets ( Morus serrator Gray, 1843), Lepidium oleraceum is found only near gannet colonies. Interestingly, Lepidium oleraceum was regarded as one of the most common plants on the foreshore of Aorangi Island, Poor Knights until the removal of pigs in 1936 ( Reynolds 1988; de Lange and Cameron 1999), yet now, despite the massive sea bird colonies covering that island, this species is scarce, being mostly confined to cliff habitats and recent slip scars ( de Lange and Cameron 1999).

These patterns suggest that the overriding need for this species is a combination of nutrient rich soils and frequent habitat disturbance to keep sites free from competition. Yet why Lepidium oleraceum is so uncommon on some naturally predator free islands which appear to meet these criteria, and why it seems to show preferences for particular bird nesting associations that can vary from island to island remains to be elucidated.

It is also possible that Lepidium oleraceum was deliberately cultivated and utilised as a pot herb by Māori who knew the species (and probably those allied to it) as “nau” (see de Lange and Norton 1996). The early writings of Banks, Solander and Forster make frequent mention of its abundance near Māori dwellings and settlements and that these people often directed Cook’s shore foraging crews to places where it could be collected ( Beaglehole 1962, 1967, 1968; Forster 1777; Hoare 1982; de Lange and Norton 1996). While it could be argued that Lepidium oleraceum flourished around coastal human habitations because these were sites of frequent disturbance and nutrient enrichment, the fact that Māori had a specific name for the plant and knew that it was edible suggests that they may also have cultivated it, a possibility that needs further critical ethnobotanical investigation.

Conservation Status.

Prior to this revision, Lepidium oleraceum was assessed as 'Threatened/Nationally Vulnerable CD, EF, RR, Sp’. Following the segregation of Lepidium oleraceum s.l. in this paper a new threat listing of Lepidium oleraceum s.s. is now necessary. As circumscribed here, Lepidium oleraceum is now confined to the Kermadec Islands, North Island (and adjacent offshore islands), northern South Island and Chatham Islands (Mangere Island only). Within this area, Lepidium oleraceum is only “common” (i.e. occurring in numbers greater than 200 individuals) on a very few islands and islets, notably Mahuki Island west of Great Barrier (Aotea Island), Karewa Island in the Bay of Plenty, Waioioi Reef off the west coast of Albatross Point, and on several islands (notably Stephens Island) within the Marlborough Sounds. It is now a very uncommon species elsewhere within this range, with most known populations comprising 50 or less mature individuals. At all known sites, populations are naturally prone to the sudden collapse and boom cycles briefly described by Norton et al. (1997) and Norton and de Lange (1999). Also, because there are few places where the Lepidium oleraceum s.s. is being closely monitored, available data on natural population fluctuations is insufficient from which to provide an overall general assessment of total population size and stability. Irrespective, the species is still very widespread in northern New Zealand and the Marlborough Sounds, and whilst most of the remaining populations are small (i.e. <50 mature plants) this may reflect a natural state of affairs, as past accounts of this species’ abundance do seem to have been exaggerated (see comments by de Lange and Norton 1996). Nevertheless, in the absence of key data on trend and rate of decline, it is difficult to provide a meaningful threat assessment, though the situation is not so difficult as to recommend a conservative assessment of 'Data Deficient’. Sufficient information exists to attempt a threat listing here, from which we recommend a conservation listing of 'Threatened/Nationally Vulnerable’ applying criterion ‘C’ of Townsend et al. (2008, p. 20-21). This assessment is based on data collected and stored by the Department of Conservation-sponsored coastal cress recovery team (P. I. Knightbridge pers comm.), from which we estimate the total population for this species at c. 3000-3500, and a rate of decline of c.10% over the next 10 years. As few wild plants last longer than three years, we have opted for (as recommended by the manual (Townsend et al. 2010)) the rate of loss rather than generation time. To that assessment the qualifiers ‘CD’ (Conservation Dependent), ‘EF’ (Extreme Fluctuations), ‘RR’ (Range Restricted) and ‘Sp’ (Sparse) still apply but we recommend the addition of ‘DP’ (Data Poor) to reflect the overall absence of trend data.

Hybridism.

Putative hybrids have between Lepidium oleraceum and Lepidium flexicaule and Lepidium obtusatum are discussed under those species.

Figures

Figure 1. Holotype of Lepidium oleraceum var. serrulatum Thell.

Figure 69. Neotype of Lepidium oleraceum G. Forst. ex Sparrm.

Figure 70. Neotype of Lepidium oleraceum var. acutidentatum Kirk.

Figure 71. Lectotype of Lepidium oleraceum var. frondosum Kirk. © Museum of New Zealand Te Papa Tongarewa.

Figure 72. Growth habit of Lepidium oleraceum on North Brother Island (image E. Dale).

Figure 75. (A) Mature and dehisced silicles of Lepidium oleraceum. (B) Mature silicle beginning to disarticulate at the base and at the apex (causing it to appear to have a notch). Scale bar = 1 mm.

Figure 76. Distribution of Lepidium oleraceum and Lepidium seditiosum.