Lepidium castellanum, 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 : 27-31

Lepidium castellanum sp. nov.

A Lepidio oleraceo sympatrico sed foliis in caule medio ad supero anguste lanceolatis ad linearo-lanceolatis dentibus acicularibus, apicibus foliorum decresento-acuminatis, et pedicellis minutis et sparsim puberuli differt, et sequentia nucleotidorum DNA distinguenda.

Holotype.

Kermadec Islands ( Fig. 26 ): Macauley Island, north-east coast, 3 July 2006, J. W. Barkla M29 & T. C. Greene, AK 297694! Isotype: CHR 552474!

Etymology.

The epithet ' castellanum ' from the Latin 'associated with a fort, fortress or castle’ refers to the remote, craggy, castle-like habitats of this species in the southern Kermadec Islands group on which islands it is endemic.

Description

( Figs 27 -32 ). Tap-rooted, strongly pungent smelling, much-branched, leafy perennial shrub, up to 1.8 × 2.0 m. Tap-root up to 800 mm long, ± napiform and/or scarcely branched. Rootstock 6-10 mm diam., woody, exposed portion smooth. Stems persistent, arising from rootstock base and basal portion of main central stem, closely packed, woody, erect, weakly angled to ± terete, glabrous; mature stems 3.8-8.2 mm diam., 0.3-1.8 m long; red-green to yellow-green, brittle, bases bearing numerous leaf abscission scars otherwise mostly leafy from mid-stem to apex at flowering; middle stems dark green to red-green, fleshy and pliant, initially ± square, prominently angled, becoming ± terete with age. Leaves coriaceous, fleshy, green to dark green, rosette-leaves absent, stem leaves withering with age; basal stem leaves 88.5-120.0 × 14.5-30.0 mm, lamina broadly lanceolate to lanceolate, margin ± deeply and ± evenly incised, teeth in 50-90 ± equal pairs, 0.5-2.9 mm long, protruding beyond leaf line, narrowly deltoid, to deltoid, leaf apex truncate-praemorse often deeply lacerate, teeth 3-5, cut 2.4-4.2 mm to lamina, narrowly deltoid, to deltoid, often bidentate, leaf base attenuate extending into a broad petiole wing; petiole distinct, 23.6-31.0 × 3.1-3.3 mm, decurrent, channelled, often with a broadly sheathing base; upper stem leaves 50.0-68.0 × 4.4-12.2 mm, decreasing in size toward inflorescences, lamina narrowly lanceolate to linear-lanceolate, margin ± deeply and ± evenly incised, teeth in 6-14 widely and evenly spaced ± pairs, 1.5-7.2 mm long, protruding beyond leaf line, narrowly deltoid, tapering, acerose, ± acicular to acicular-falcate; lamina apex acute (rarely truncate-praemorse), acuminate, acumen 5.8-11.0 mm long, margins of acumen toothed, teeth often bidentate, 8-10 mm long, acerose, often acicular, or acicular-falcate, leaf base attenuate extending into a narrow petiole wing; petiole distinct, 2.9-8.2 × 1.2-3.3 mm, decurrent, channelled, often with a broadly sheathing base. Inflorescences racemose, 50-100 mm long at fruiting; rachis 0.5-2.25 mm diam., terminal and lateral, leaf-opposed, often long-persistent, sparsely to densely covered in pale, patent, ± clavate hairs or rarely glabrous, hairs 0.1-0.14 mm long; pedicels 5.6-7.2 mm long at fruiting, erecto-patent, with sparse, pale, patent, clavate hairs on adaxial surface, hairs 0.1-0.12 mm long. Flowers 3.0-4.5 mm diam., fragrant. Sepals 4, saccate, ± overlapping at base, lateral sepals broad, 0.5-1.5 mm diam., orbicular, pale to dark green with a broad white, ± undulose margin, apex rounded to obtuse, abaxial surface often hairy, hairs 0.2-0.4 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, 1.1-2.0 × 1.0-1.6 mm, spreading, claw 0.4-0.8 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 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, 2.4-3.6 × 1.8-2.5 mm, elliptic to rhomboid, apex acute and tapering, valves green maturing grey-white, glabrous, scarcely separating at apex at maturity, not winged; style 0.3-0.7 mm long, exserted. Seeds 2, 1.3-1.9 × 0.8-1.6 mm, narrowly to broadly ovoid, brown to orange-brown, not winged. FL Jul-Jun. FR Sep-Jul.

Representative Specimens.

Kermadec Islands: Curtis I., 18 July 1969, W. R. Sykes 836/K, (CHR 193789); Haszard Islet, 21 July 2002, T. Greene s.n., P. Dilks & P. Scofield, (AK 258039); Cheeseman Island, 19 November 1971, W. R. Sykes 932/K, (CHR 211838); Cheeseman Island, 26 July 2002, T. Greene s.n., P. Dilks & P. Scofield, (AK 258038);Cheeseman Island, "Te Mimi Paora Rock", 24 May 2011, P. J. de Lange K850, (AK 326008); Cheeseman Island, "The Castle", 24 May 2011, P. J. de Lange K851, (AK 326009); Cheeseman Island, "The Castle", 24 May 2011, P. J. de Lange K852, (AK 326010). Cultivated (New Zealand): ex Curtis I. from CHR 193789, 9 January 1970, W. R. Sykes 901/K, (CHR 20188A); ex. Curtis I. from CHR 193789, 25 February 1971, W. R. Sykes 901/K, (CHR 201088B); Lincoln, ex Macauley Island, Landcare Research experimental nursery, 10 July 2008, P. B. Heenan s.n., (CHR 609796); Lincoln, ex Macauley Island, Landcare Research experimental nursery, 2 October 2009, P. B. Heenan s.n., (CHR 609806).

Distribution

( Fig. 15 ). Endemic. Kermadec Islands (Macauley Island, Curtis Island, Haszard Islet and Cheeseman Island).

Recognition.

Lepidium castellanum is distinguished by its very robust, shrubby growth habit ( Fig. 27 ), sometimes up to 1.8 × 2.0 m, erect, often closely packed, usually leafy stems, narrowly lanceolate to linear-lanceolate upper stem leaves, and by the very long, needle-shaped teeth of the leaves which reach well beyond the leaf margin ( Figs 28 -30 ). In this species, the pedicels (and often the inflorescence rachises) are minutely hairy ( Fig. 31 ), whilst those of Lepidium oleraceum are glabrous. Lepidium castellanum is sympatric with Lepidium oleraceum on Curtis Island. Elsewhere, in northern New Zealand, especially on the Poor Knights and Hen (Taranga) islands, narrow-leaved forms of Lepidium oleraceum are also common. However, these plants have a much smaller growth habit, their leaves lack the distinctive long needle-shaped teeth and long-acuminate leaf apices of Lepidium castellanum , and, as with Lepidium oleraceum populations elsewhere, their pedicels are glabrous.

Ecology.

Lepidium castellanum is a sparse associate of the vegetation that has colonised the soft, erosion-prone cliff tops of Macauley Island, the less geothermally active summit slopes of Curtis Island, and the rocky tops of Haszard Islet and Cheeseman Island. On Macauley Island, Lepidium castellanum was recorded from open or sparsely vegetated, petrel-burrowed ground where it formed windswept shrubs in association with the creeping Scaevola gracilis Hook.f., tangles of Ipomoea cairica (L.) Sweet., Disphyma australe subsp. stricticaule Chinnock and Polycarpon tetraphyllum (L.) L. ( Barkla et al. 2008; J. W. Barkla and T. C. Greene pers. comm.). On Curtis Island, it has been recorded growing amongst Disphyma australe subsp. stricticaule, while on the extensively seabird-burrowed Haszard Islet, it is one of the main shrub species, growing there in association with Myoporum rapense subsp. kermadecense (Sykes) Chinnock, Cyperus insularis Heenan et de Lange, Tetragonia tetragonioides (Pall.) Kuntze, and Parietaria debilis G.Forst. On Cheeseman Island, numerous seedlings and a few adults were seen in 2011 growing on heavily petrel-burrowed soil covered ledges amongst Disphyma australe subsp. stricticaule, and also as a few sub-adults within an active petrel colony in a narrow gully, growing in association with Cyperus insularis , Tetragonia tetragonioides , and Parietaria debilis .

Conservation Status.

Lepidium castellanum is confined to the Southern Kermadec Island group (see de Lange et al. 2004), part of the Kermadec Islands Nature Reserve. Within the southern Kermadec Islands group it has been recorded from Macauley Island, Cheeseman Island, Curtis Island, and from Haszard Islet. On Macauley Island it was recorded twice, in 2002 and 2006 ( Barkla et al. (2008); T. C. Greene pers. comm.), at that time numbering at best five or fewer individuals. However, it was not seen on Macauley Island in 2011 ( de Lange 2012; de Lange in press). In 2002 and 2006, the summit of Haszard Islet (6 ha, of which c.2.1 ha is vegetated) was thoroughly explored during helicopter-assisted landings by ornithologists. During those visits, it was noted that Lepidium castellanum was one of the major shrub-forming species on the richly manured and petrel-turbated soils of that islet’s summit slopes (T. C. Greene and K. Baird pers. comm.). While accurate counts of the number of plants present on Haszard Islet were not made, it would seem that on both visits the islet summit supported approximately 20-50 individuals (T. C. Greene and K. Baird pers. comm.). Further south, its status on Curtis Island remains unknown, as there have been no gatherings of Lepidium from there since 1969, and several visits during the 1980s and in 2002 did not see it there (G.A. Taylor and T. C. Greene pers. comm.). However, on nearby Cheeseman Island, a 7-ha island (of which c.5.6 ha is vegetated) two plants were recorded in 2002 during a brief helicopter assisted 40 minute visit (T. C. Greene pers. comm.). Later, in 2011, nine adults and an estimated 1000 seedlings were noted on Cheeseman Island during a thorough botanical investigation of that island ( de Lange 2012). Therefore, to the best of our knowledge there are between 20 and 50 adults on Hazard Islet and nine mature plants on Cheeseman Island, while the status of this species on Curtis Island and Macauley Island is uncertain. Therefore Lepidium castellanum qualifies as 'Threatened/Nationally Critical’ either because the total number of plants in the wild is <250 (criterion A(1) of Townsend et al. (2008)) or because the combined area of occupancy is <1 ha (criterion A(3) of Townsend et al. 2008). To that assessment we add the qualifiers ‘DP’ (Data Poor) and ‘IE’ (Island Endemic). Data Poor ( ‘DP’) is recommended because of the lack of accurate counts of wild plants from Haszard Islet, absence of any recent survey for the species on Curtis Island, and lack of any trend data.

Figures

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

Figure 26. Holotype of Lepidium castellanum de Lange et Heenan.

Figure 27. (A) Wild plant of Lepidium castellanum on cliff top of Macauley Island showing growth habit (plant growing with Scaevola gracilis, Tetragonia tetragonioides and Disphyma australe subsp. stricticaule) (image: J. W. Barkla).

Figure 28. Young inflorescences and upper-stem leaves of Lepidium castellanum (image: J. W. Barkla).

Figure 30. C lose up of basal-stem leaf of Lepidium castellanum on Cheeseman Island (image: W. Chinn).

Figure 31. Pedicel hairs of Lepidium castellanum. Scale bar = 1 mm.

Figure 32. Mature silicle of Lepidium castellanum. From holotype (AK 297694). Scale bar = 1 mm).