Corybas obscurus Lehnebach, 2016

Lehnebach, Carlos A., Zeller, Andreas J., Frericks, Jonathan & Ritchie, Peter, 2016, Five new species of Corybas (Diurideae, Orchidaceae) endemic to New Zealand and phylogeny of the Nematoceras clade, Phytotaxa 270 (1), pp. 1-24 : 11

2. Corybas obscurus Lehnebach , sp. nov. ( Fig. 7A–C)

Type:— NEW ZEALAND. South Island: Nelson Lakes National Park, Lake Rotoiti, along Lakeside track, near Whisky falls, 25 November 2011, Lehnebach & Zeller SP104133 (holotype: WELT!).

Diagnosis:—Similar to C. confusus in lip colour but differs by its short dorsal sepal firmly appressed against the upper margins of the labellum and reniform to cordiform leaf. It differs from C. trilobus by the overall non-transparent, dark maroon to black flower.

Terrestrial herbs, 14–30 mm tall at flowering. Leaf distinctly petiolate, petiole (5.1)14.2–23.1(40.8) mm long; lamina reniform to cordiform, (5.8)10.9–13.4(18.2) × (9.6)16–21.5(26.7) mm; margin entire; apex mucronate with mucro (1.1)15–2.2(2.5) mm long. Flower solitary, held erect on a peduncle (2.0)3.6–5.3(7.8) mm long, floral bract triangular to sub-triangular when flattened, (2.3)3.6–5.8(7.7) × (1.5)2.1–2.6(4.0) mm; dorsal sepal dark red to dark maroon to black, arching over the labellum, concave to cucullate, narrow at the base and widely spathulate towards the tip, apex retuse to emarginated; lateral sepal linear-filiform, crimson to dark red, (11.7)16.1–18.0(20.6) mm long; petals similar to the lateral sepals but longer, (27.3)35.7–43.6(57.2) mm long; labellum mostly dark crimson to almost black with a pale green centre, auriculate at base, aperture (1.6)1.7–2.1(2.4) mm in diameter; lamina deflexed, ca. 10 mm wide, with a central groove formed by the inwards folding of the lamina, extending downwards almost to the lower margin and sunken pit formed at the point where the lamina bends, margin incurving, mostly entire but erose at the lower edge, inner surface of the labellum covered glandular trichomes. Ovary (3.0)4.6–7.0(8.4) mm long. Column 1.6 mm long, curved, retuse column wings at either sides of the stigma.

Specimens examined: — SOUTH ISLAND: Nelson Lakes National Park, Cascade track. 26 November 2011, Lehnebach & Zeller SP104134 ( WELT) ; Nelson Lakes National Park, St Arnaud Range track, 27 November 2011, Lehnebach & Zeller SP10413527 ( WELT) ; Nelson Lakes National Park, Mt Robert road, 9 November 2012, Lehnebach, Moorhouse & Upson SP104152 ( WELT) ; Nelson Lakes National Park, Lake Rotoiti, Lakeside track from Mt Robert road to Coldwater hut, near Whiskey falls , 25 November 2011, Lehnebach & Zeller SP104404 ( WELT) ; Nelson Lakes National Park, Lake Rotoiti, Lakeside track from Mt Robert road to Coldwater hut, 25 November 2011, Lehnebach & Zeller SP104405 ( WELT) .

Etymology:— A reference to the dark colour of the flower.

Distribution:— Endemic to NZ. Only known from Nelson Lakes National Park in the South Island and nearby forested areas ( Fig. 7D).

Habita t:—Found in leaf litter under southern beech forest ( Fuscospora or Lophozonia , Nothofagaceae ] or Myrtaceae scrub, 600–1000 m.

Phenology:— Flowering October to early November; fruiting September to December.

Conservation status:—This species is common within the limits of Nelson Lakes National Park and nearby forested areas. According to Scanlen & St. George (2011) it also occurs in a few sites of the upper South Island, but we were not able to find any photographic or voucher material to confirm whether these sightings correspond to C. obscurus . Based on our field observations and following the New Zealand Threat Classification System ( Townsend et al. 2008), we suggest C. obscurus should be ranked as Naturally Uncommon.