Uncinia auceps de Lange et Heenan, 2013

Lange, P. J., Heenan, P. B. & Rolfe, J. R., 2013, Uncinia auceps (Cyperaceae): a new endemic hooked sedge for the Chatham Islands, Phytotaxa 104 (1), pp. 12-20 : 16-19

Uncinia auceps de Lange et Heenan , sp. nov.

Diagnosis:—Distinguished from Uncinia uncinata by the mature fruiting culms which are greatly elongated, drooping and long trailing; by the more numerous female florets; and by the persistent rather than deciduous glumes.

Type ( Fig. 5 ):— NEW ZEALAND. Chatham Islands, Chatham Island, Te Whanga Lagoon, Nikau Scenic Reserve , P. B . Heenan & P. J . de Lange CH 1607, 1 Jun 2008 (holotype CHR 602500 A-B; isotype AK 304677) .

Description:—Large, caespitose plants, with shortly spreading, erect rhizomes. Mature culms (0.8–)1.2–2.0 m long, (0.6–)0.8–1.0 mm wide, glabrous, trigonous, greatly exceeding leaves, trailing; leaf sheaths up to 6 cm long, dark brown, prominently and deeply nerved, nerves concolorous with sheath. Leaves 4–8(–12) per culm, 48–68(–83) cm long, 4.3– 5.7(–6.2) mm wide, deeply channelled, upright to spreading, curved, dark green; adaxial surface scabrid in distal portion, otherwise glabrous; abaxial surface keeled, keel ± scabrid, often diffusely so, sometimes nearly glabrous, rest of surface glabrous margin scabrid, apex acute, trigonous, scabrid. Spikes 9–20(–40) cm long, 3–6 mm wide, linear, often curved and twisted; female florets proximal, 80–420 per spike; internodes up to 7 mm long at base, decreasing to 0.4 mm long (or sometimes less) above; male florets distal, 60–100 or more, imbricate. Spike sometimes subtended by a foliose bract; bract 9.0– 11.2 cm long, 0.2–1.2 mm wide, capillary, channeled, margins and abaxial midrib scabrid, apex trigonous. Glumes persistent. Male glumes, imbricate, 3.0–4.2(–5.1) mm long, 1.0– 1.8 mm wide, lanceolate, elliptic-lanceolate to narrowly elliptic, dark to light lustrous brown at maturity, midrib prominent, stramineous, with 1 central nerve, apex acute, margins membranous, entire, apices sometimes scabrid to ± lacerate. Filaments 3.6–5.0 mm long, pale brown; anthers, 1.2–1.8 mm long, yellow. Female glumes 3.4–5.3 mm long, 1.0–2.0 mm wide, ± equal in length to utricles, elliptic-lanceolate to narrowly elliptic, dark to light lustrous brown at maturity, midrib prominent, with 1 central nerve, usually concolorous with rest of glume, sometimes stramineous, especially at distal portion of spike, apex acute to subacute, margins membranous, entire; lowest 1(–2) glumes sometimes bearing foliose, slender (almost capillary), filiform awns up to 6 cm long, these mostly entire except for scabrid upper abaxial midrib and apex, apex trigonous. Utricles scarcely spreading when ripe, 4.8– 5.3 mm long, 1.2–1.4 mm wide, plano-convex to convex, ovoid, glabrous, lustrous brown to dark brown, lateral nerves ± prominent, though not conspicuous, stipe and beak narrow, each 1.0– 1.5 mm long; rachilla 7.0– 9.2 mm long. Nuts 2.2–2.4 mm long, 1.0– 1.2 mm wide, ovoid, light grey to silvery grey, papillate. FL: Aug–Oct. FR: Jan–Nov. Chromosome number 2 n = 88 ( Murray & de Lange 2013).

Representative specimens:— CHATHAM ISLANDS: Rekohu (Chatham Island): Te Hapupu, J. M. Barker Hapupu National Historic Reserve , 5 Jan 2007, E. K. Cameron 14182 ( AK 298929); Nikau Scenic

Reserve, 1 Jun 2008, P. B . Heenan & P. J . de Lange CH 1609 ( CHR 602520 A-E); south of Lake Huro , 16 Sep 1968, M. A. & I. M ., Ritchie s.n. ( CHR 178675 ); Nairn Valley , 20 Sep 1968, M. A. & I. M ., Ritchie s.n. ( CHR 178673 ); Tuku-a-Tamatea Nature Reserve , 26 Feb 1996, P. J . de Lange CH 138 & G. M . Crowcroft ( AK 230477); Tuku-a-Tamatea Nature Reserve , 2 Jun 2008, P. B . Heenan & P. J . de Lange CH 1618 ( CHR 596837 ); Tuku-a-Tamatea Nature Reserve , 2 Jun 2008, P. B . Heenan & P. J . de Lange CH 1619 ( CHR 602512 , AK). Rangiauria (Pitt Island): Glory, 23 Aug 1968, M. A. & I. M ., Ritchie s.n. ( CHR 178641 A-B); ‘ Caravan Bush’ [Ellen Elizabeth Preece Conservation Covenant], 30 May 2008, P. B . Heenan, P. J . de Lange CH 1545 & G . Houliston ( CHR 602439 ). Rangatira (South East Island): Feb 1980, G. N . Park 47 ( CHR 399094 ); ‘central swamp’, Jan 1991, G. A. S . Taylor s.n. ( AK 296156, CHR, WELT) .

Recognition:—Prior to our field work on the Chatham Islands the distinctive nature of Uncinia auceps had been overlooked by past field botanists and in treatments of the New Zealand species of Uncinia (see Hamlin 1959; Moore & Edgar 1970). This was possibly because the majority of collections made from those islands during that time were of individuals that had been sampled prior to the final stages of the maturation of the fruiting culms (e.g., M. A. & I.M., Ritchie s.n. (CHR 178673); M. A. & I.M., Ritchie s.n. (CHR 178641A- B); G.N.Park47 (CHR 399094)). Therefore, the distinctive elongation and trailing habit of the mature fruiting culms had not been observed or collected. Indeed, mature fruiting specimens of U. auceps without critical inspection appear to be vegetative ( Fig. 2A ) as the fruiting, elongated culms are partially obscured by trailing on the ground. It is only when the fruiting plants are lifted above the ground that the long trailing and fruiting culms become readily apparent ( Fig. 2B ). Because of this feature, it would seem that visiting field botanists working on the islands may have treated Uncinia auceps as an undetermined Carex spp. This confusion may explain past Chatham Islands records of Carex lambertiana Boott ( Hooker 1853: 284) records which, in the absence of herbarium specimens so named, we had previously attributed to the very different looking, peat bog endemic, C. chathamica Petrie ( Petrie 1915: 55) (see de Lange et al. 2011). Carex lambertiana is a forest dwelling sedge of North Island and northern South Island which, when vegetative, has a remarkable similarity to Uncinia auceps .

It also seems likely that Uncinia auceps , at least in those early-season specimens in which the culm elongation has yet to develop, is the basis for past literature records of the very different U. clavata and U. ferruginea (see de Lange et al. 2011). This may be because the glumes of U. auceps are equal in length to the utricles, a character which if used in isolation, aligns U. auceps with U. clavata and U. ferruginea in the key to the genus in Moore & Edgar (1970). Nevertheless, on the basis of utricle diameter, that key if used correctly places U. auceps within the range of U. uncinata ( Moore & Edgar 1970) . Uncinia auceps is superficially similar to U. uncinata ( Fig. 3 ), differing from that species by the elongation of the mature fruiting culms ( Fig. 2B , 5 ). Vegetatively, U. auceps falls within the range of U. uncinata . In fruiting material ( Fig. 4 ), the spikes of Uncinia auceps can be much longer (up to 40 cm long in U. auceps ; cf. 20 cm long in U. uncinata ) though there is considerable overlap within the usual range of both species (usually 9–20 cm long in U. auceps ; 5.5– 20.0 cm long in U. uncinata ). However, the glumes are diagnostic ( Fig. 4 ), as those of U. auceps are not deciduous ( Fig. 4C , whilst those of U. uncinata are deciduous ( Hamlin 1959; Moore & Edgar 1970), and the glumes of U. auceps are equal to ( Fig. 4 C-D), rather than mostly less than the length of the utricles (Fig. A-B) (the usual condition of U. uncinata ( Moore & Edgar 1970) . Uncinia auceps also has more female florets (80– 420; cf. 60–120 in U. uncinata ( Moore & Edgar 1970)) .

Distribution:— Uncinia auceps is endemic to the Chatham Islands where it is known from most of the main islands. It is, however, apparently absent from natural forested areas on Mangere and Little Mangere islands.

Habitats:— Uncinia auceps is an abundant ground cover in most forested areas. Due to the hooked rachilla, mature utricles are readily dispersed by human traffic and therefore the Uncinia is especially common along tracksides and around forest huts and other shelters. It is also reasonably common along stream and river sides, in forest on rubbly ground, slip scars, and growing at the ecotone between forest, rough pasture and/or fernland.

In these habitats it is frequently associated with indigenous and naturalised ground cover plants such as Australina pusilla Gaudich. subsp. pusilla (Gaudichaud-Beaupré:1830: 505), Bellis perennis L. (Linnaeus 1753: 886), Callitriche muelleri Sond. (Sonder 1856: 229) , Carex ventosa C.B.Clarke (Cheeseman 1906: 832) , Corybas Salisb. spp. (Salisbury 1807: 83) , Hydrocotyle heteromeria A.Rich. (Richard 1820: 200) , Myosotis spathulata G.Forst. (Forster 1786: 12) , Plantago raoulii Decne. (de Candolle 1852: 703), Poa imbecilla Spreng. (Biehler 1907: 9) , Ranunculus reflexus Garn. -Jones (Garnock-Jones 1987: 126), Veronica arvensis L. (Linnaeus 1753: 13), and Veronica serpyllifolia L. (Linnaeus 1753: 12).

While Uncinia auceps reaches its greatest abundance in the denser, wetter, less disturbed forested parts of the main Chatham Islands, it is also reasonably tolerant of the open, drier forest types. These include the mixed Myrsine chathamica F.Muell. (von Mueller 1864: 38) - Corynocarpus laevigatus J.R.Forst. et G.Forst. (Forster & Forster 1776: 32) and Olearia traversiorum (F.Muell.) Hook (Hooker 1867: 731–732) forests that have developed on limestone outcrops and sand dunes. In these locations, though less common, it is usually found growing in association with Carex ventosa , Parietaria debilis G.Forst. (Forster 1786: 73) and Tetragonia implexicoma (Miq.) Hook. f. (Hooker 1857: 148).

Conservation status:— Uncinia auceps is a widespread and common sedge in the denser forested parts of the main islands of the Chathams group. On Rekohu it reaches its greatest abundance in the forests of the southern tablelands, especially within the Tuku-a-Tamatea Nature Reserve. Large populations also occur in privately owned forest remnants near Matakitaki, along Te Whanga Lagoon, and in reserves at Nikau Bush and the Taia Peninsula. On Rangiauria it is common in all the larger forest remnants, as is also the case on Rangatira (South East Island). While not all of the areas in which Uncinia auceps grows are formally protected, the species is nevertheless well represented in the islands’ reserve network. However, reservation is no guarrantee of long-term security as not all reserves are secure from browsing animals, and, in some reserves, such as Waipaua Scenic Reserve on Rangiauria, the impact of pigs and wild sheep on the ground and shrub layers is extremely severe. Thus, although numerically abundant in these reserves, as these only occupy a small part of its range, Uncinia auceps is still in slow decline through ongoing deterioration, loss of habitat and direct browse pressure outside reserved areas. Therefore, Uncinia auceps with an estimated total population of> 100 000 individuals, and a predicted ongoing decline of at least 10% in the area of occupancy over the next three generations, is assessed here as ‘At Risk / Declining’ (pathway C1/1) of Townsend et al. (2008). This conservation status reflects that, outside those formally and privately protected forested remnants, the long-term security of the habitat occupied by the sedge is not assured. If not halted, ongoing decline, will result in the future loss of this sedge from many parts of its current range. To this conservation status we recommend appending the qualifiers ‘IE’ (Island Endemic) and ‘PD’ (Partial Decline), the latter because outside well managed, reserved sites, Uncinia auceps populations are believed to be in gradual decline.

Etymology:—The subspecies epithet ‘ auceps ’ is taken from the Latin noun for a ‘bird catcher’. The epithet alludes to the mature fruiting inflorescences which occur sprawling and lying on the ground, usually to some distance from the parent plant, and often hidden among associated grasses and herbs. It is thus easy to visualise the hooked fruits of the inflorescences catching in the feathers of the now extinct endemic suite of flightless rails that once frequented the Chatham Islands forest floors ( Tennyson & Martinson 2006).

Figures

FIGURE 2. Uncinia auceps. A, mature fruiting plant growing on forest floor (Tuku-a-Tamatea Nature Reserve, Rekohu (Chatham Island)); B, portion of live plant showing mature elongated, trailing culms (Nikau Bush, Rekohu (Chatham Island).

FIGURE 3. Mature fruiting plant of Uncinia uncinata (Lower Hutt, North Island, New Zealand).

FIGURE 4. Mature fruiting inflorescences, glumes and perigynium of Uncinia uncinata and U. auceps. A, portion of mature fruiting inflorescence of U. uncinata showing deciduous glumes (Silverstream Scenic Reserve, North Island, New Zealand); B, glume and perigynium of U. uncinata (Silverstream Scenic Reserve, North Island, New Zealand); C, portion of mature fruiting inflorescence of U. auceps showing persistent glumes (Nikau Bush, Rekohu (Chatham Island); D, glume and perigynium of U. auceps (Nikau Bush, Rekohu (Chatham Island).

FIGURE 5. Holotype of Uncinia auceps spread over two sheets (A,B) (Heenan & de Lange CH1607, CHR 602500A,B).