‘Mt Arthur’ A. McKay s.n., 1874, (WELT SP059605!) (fideZotov 1971).

Named by Zotov (1971) for John Buchanan FLS (1819–1898), Scottish born draughtsman, and New Zealand’s first government employed botanist (Taylor 2002). Buchanan first described Simplicia buchananii as a species of Poa, P. uniflora Buchanan but that species name was preoccupied (P. uniflora Muhl.) (Zotov 1971).

(Fig. 5). Plants gracile, tufted, 0.40–0.60(–1.0) m tall. Culms 0.40–0.80 m long, bright green when fresh, wiry, erect (sometimes with apices weakly pendant), culm internodes 3–5, elongated, glabrous; internodes ± equal in length to subtending leaf-sheaths. Culm-nodes slightly swollen when fresh, glossy orange-brown to dark red-brown (0.1–)0.3–0.4(–0.5) mm long. Basal leaf-sheaths stramineous or dull brown, membranous, strongly ribbed, usually glabrous, sometimes scabrid on ribs or evenly, finely pubescent; hairs when present retrorse to patent, minute (0.06–0.08 mm long); mid stem and upper leaf-sheaths stramineous to green, membranous, strongly ribbed, glabrous. Ligule 2.0–3.5(–4.0) mm, membranous, lanceolate, apex erose to very deeply lacerate; glabrous. Leaf-blade 100–200 × (1.8–)3.0(–4.0) mm, green to yellow-green, flat, linear-lanceolate with acuminate apices, finely ribbed; adaxial ribs finely scabrid, abaxial ribs glabrous; margins smooth. Panicle (40–)160(–180) mm long, linear; rachis glabrous, branches (10–)30(–36) mm long, erect, glabrous (sometimes bearing minute antrorse prickle-teeth near pedicels), bearing spikelets almost to base, pedicels 0.6–1.0(–1.2) mm long, ± glabrous (sometimes bearing sparse, minute, antrorse prickle-teeth), ± appressed to branchlets. Spikelets 2.8–3.0 mm, 1(–2)-flowered, lanceolate, light green to stramineous. Glumes green (± hyaline), glabrous, ovate-lanceolate to ovate, acute to subacute, 1-nerved, lower and upper glume margins entire, ciliate; lower glume 0.3–1.0 mm, upper glume 1.0(–1.6) mm. Lemma 2.6–3.0 mm, light green to grey, scabrid (densely covered in minute prickle-teeth), 3(–5)-nerved, ovate-lanceolate, acute to mucronate, sometimes with a minute subapical awnlet 0.06-0.08 mm long. Palea 2.4–2.8 mm, scabrid (densely covered in minute prickle-teeth), lanceolate, pale green to green, pubescent, 1–2-nerved. Rachilla prolongation 0.3–0.5 mm, filiform, hyaline, glabrous. Stamens 3. Filaments 0.3 mm long, hyaline. Anthers 0.7–1.5 mm, purple or yellow. Ovary narrowly ovoid to weakly trigonous 1.0–1.25 mm long, green, ± glabrous (basal portion sometimes minutely ciliate); styles apical, 0.10–0.25 mm, hyaline; stigmas plumose, white. Caryopsis 1.3–1.5 mm long, laterally compressed, orange when mature. Chromosome number: 2n = 28 (Zotov 1971).

Figure 5. 

Simplicia buchananii. A habitat, Kahurangi National Park, North West Nelson, South Island, New Zealand B growth habit and inflorescence C culm, leaf base, sheath and ligule D spikelet showing reduced glumes and lemma (images: J.R. Rolfe).

North-West Nelson, Gouland Downs, A.P. Druce s.n., Jan 1969, WELT SP069213; North-West Nelson, Cobb Valley, Chaffey’s Stream, A.M. Hamilton s.n., 23 Feb 1965, CHR 119546; North-West Nelson, Peel Range, above Lake Henderson, A.P. Druce s.n., Mar 1982, CHR 369973; North-West Nelson, below Balloon Hut, I.M. Ritchie s.n., 29 Mar 1967, CHR 175738; North-West Nelson, Kahurangi National Park, Cundy Creek, M.J. Thorsen 101/09, 11 Apr 2009, AK 304802; North-West Nelson, Kahurangi National Park, west of Gordon’s Pyramid, M.J. Thorsen 106/09, 12 Apr 2009, AK 305801; North-West Nelson, Mt Arthur, ?A. Mackay s.n., c.1879, CHR 13277; North-West Nelson, South Arthur Range, west side of Baton Saddle, A.P. Druce 478, Feb 1991, CHR 469403; North-West Nelson, Lockett Range, near Ruby Lake, A.P. Druce s.n., Jan 1982, CHR 387666–387667; North West of Mt FZ (between Glenroy and Sheriff Rivers), A.P. Druce s.n., 13 Mar 1984, CHR 394262.

(Fig. 1). Simplicia buchananii is endemic to North-West Nelson, South Island.

Simplicia buchananii is distinguished from S. laxa and S. felix by the tufted growth habit, erect culms, and by the linear inflorescences, whose branches are usually tightly appressed to the rachises (Fig. 5, for other differences see Table 1).

Simplicia buchananii is a biologically sparse species of calcareous rock habitats (including shaded rock outcrops, boulderfalls, rock overhangs and cave entrances) within montane forest (de Lange et al. 2010).

Using the New Zealand Threat Classification System (Townsend et al. 2008) Simplicia buchananii has been assessed as ‘Threatened / Nationally Critical’ with the qualifiers ‘DP’ [Data Poor], ‘RR’ [Range Restricted] and ‘Sp’ [Sparse] (de Lange et al. 2013). The threats this species faces were summarised by de Lange et al. (2010) and Smissen et al. (2011). Based on our current knowledge of this species the current threat status remains appropriate.

‘Waikouaiti, Otago’ D. Petrie s.n., n.d. (WELT SP043017!) (fideZotov 1971)

‘Waikouaiti, Otago, D.Petrie s.n., n.d. (WELT SP043021!) (fideZotov 1971)

Kirk (1897) did not explain the meaning of his species epithet ‘laxa’ though his intent is clear from his protologue where he describes the new species as having ‘weak, decumbent, flaccid’ culms. The epithet is derived from Latin ‘laxus’ meaning ‘loosely arranged’ as in ‘wide, loose’ structures or growth (Taylor 2002).

(Fig. 6). Plants trailing forming thick sprawling mats or diffuse interconnected patches up to 0.6 m across. Culms 0.40–0.80 m long, green to pale-green when fresh, wiry, decumbent, with the apices weakly erect, culm internodes 4–8, elongated, sparsely (sometimes densely) hairy, or glabrous; hairs weakly flexuous, patent up 0.18 mm long; internodes usually shorter than subtending leaf-sheaths. Culm-nodes conspicuously swollen when fresh, maroon-black to black (0.13–)0.18–0.30 mm long, rooting freely on contact with ground. Basal leaf-sheaths glossy light brown to amber, membranous, ribbed, abaxially (often copiously) pubescent on ribs (and usually on interstices), hairs 0.20–0.25(–0.30) mm long, patent to retrorse; mid stem and upper leaf-sheaths pale-green to green, membranous, ribbed, abaxially pubescent on ribs (and sometimes on interstices), hairs copious, 0.35–0.40 mm long patent, mostly straight, sometimes curved or weakly flexuous. Ligule 2.8–3.5(–10) mm, membranous, lanceolate, apex erose to very deeply lacerate; abaxially sparsely to copiously hairy; hairs 0.20–0.24 mm long. Leaf-blade (100–)160(–200) × (2.8–)3.0(–3.6) mm, green to dark green, flat, linear-lanceolate, finely ribbed; adaxial ribs finely pubescent, abaxially glabrous (sometimes sparsely hairy at leaf base; margins ± smooth, sometimes irregularly finely scabrid and sparsely hairy. Panicle (40–)100(–150) mm long, linear to ± pyramidal, usually with basal branch or branch pair reflexed (often unevenly so); rachis glabrous, branches (20–)40(–60) mm long, finely, antrorsely hairy (hairs 0.20–0.25 mm long), binate, initially contracted but as inflorescences mature, spreading to reflexed, devoid of spikelets in lower half; pedicels appressed to branchlets, 1.00–1.06 mm long, finely pubescent. Spikelets 2.8–3.2 mm, 1-flowered, lanceolate, light green. Glumes pale green (± hyaline), glabrous, broadly ovate-lanceolate to ovate, acute, 1-nerved, nerve extending beyond apex as a minute mucro, lower glume margins entire (sometimes with apex erose), ciliate towards apex, upper glume margins usually erose (sometimes subentire), ciliate; lower glume 0.5–0.8 mm, upper glume 0.75–1.0(–1.2) mm. Lemma 2.8–3.2(–3.4) mm, light green to grey-green (sometimes purple-green), ± evenly, densely pubescent, lanceolate, acute, apex mucronate (mucro 0.10–0.25 mm long), 3(–5)-nerved (nerves obscured by hairs); lemma hairs antrorse appressed, sericeous, 0.12–0.13 mm long. Palea 2.4–2.8 mm, lanceolate, pale green to green, pubescent, 1–2-nerved, (nerves obscured by hairs). Rachilla prolongation 1.25–1.30 mm, narrowly lanceolate, hyaline, margins minutely ciliate. Stamens 3. Filaments 0.20–0.25 mm long, hyaline. Anthers 0.30–0.45 mm, yellow. Ovary narrowly ovoid to weakly trigonous 1.0–1.25 mm long, dark green, ± glabrous (basal portion sometimes minutely ciliate); styles apical, 1.10–1.25 mm, hyaline; stigmas plumose, white. Caryopsis 1.4–1.5 mm long, laterally compressed, orange-brown when mature. Chromosome number: 2n = 28 (Zotov 1971, I.M. Ritchie s.n., CHR 202752)

Figure 6. 

Simplicia laxa. A habitat, Emerald Stream, McCraes, North Otago, South Island, New Zealand (image D.A. Houston) B growth habit and inflorescence C culm, leaf base, sheath and ligule D spikelet showing reduced glumes and lemma. (Photo credit images C and D: K. Ford, Allan Herbarium, Landcare Research Manaaki Whenua)

Karamea, Honeycomb Cave, P. Wardle s.n., 22 Jan 1985, CHR 489550; Karamea Ecological District, Karamea, Kahurangi National Park, Honeycomb Cave, P.J. de Lange 4774, 6 Dec 2000, AK 252968; Otago, Taieri County, near Deep Stream Hotel, Rock & Pillar Road, D. Petrie s.n., Feb 1877, WELT SP010498, WELT SP043018, WELT SP043020A, WELT SP043020B, WELT SP043020C, WELT SP069211; Old Man Ecological District, Old Man Range, Castle Rock Summit, P.J. de Lange 7859, 18 Jan 2008, AK 304848 (Duplicate: US); Old Man Ecological District, Old Man Range, Castle Rock Summit (south side), P.J. de Lange 7858, 18 Jan 2008, AK 304847; Macraes Ecological District, Nenthorn, Deighton Stream tributary, ‘John’s Cave’, P.J. de Lange 7206 & M.J. Thorsen, 15 Jan 2008, AK 301580; Macraes Ecological District, Nenthorn, Upper Emerald Stream, P.J. de Lange 7835 & M.J. Thorsen, 15 Jan 2008, AK 304808; Macraes Ecological District, Nenthorn, Upper Emerald Stream, P.J. de Lange 7836 & M.J. Thorsen, 15 Jan 2008, AK 304809; Macraes Ecological District, Nenthorn, Emerald Stream, ‘Old Otagense site’, P.J. de Lange 7856 & M.J. Thorsen, 15 Jan 2008, AK 304845 (Duplicate: US); Summerhills Station, 3 O’Clock Stream, M.J. Thorsen 100/07, 14 May 2007, CHR 591912; Nevis Valley, Barn Creek, G. Loh s.n., 26 Nov 1994, CHR 509148. CULTIVATED: Ex. Cult., Karamea Ecological District, Karamea, Kahurangi National Park, Honeycomb Cave, P.J. de Lange 6104, 3 Sep 2004, AK 288071 (Duplicate: HO). Macraes Ecological District, north-east of Nenthorn, Macraes, Emerald Stream, T Whitaker Falcon Site, M.J. Thorsen s.n., 30 Mar 2006, AK 295631; Ex. Cult., Central Otago, Old Man Range, Castle Rock, I.M. Ritchie s.n., 25 Oct 1969 (grown on and harvested by V.D. Zotov on 31 Dec 1970 as G8128).

(Fig. 1). As recircumscribed here Simplicia laxa is now endemic to the South Island. Nevertheless, there are a few historical collections held in world herbaria that suggest that S. felix and S. laxa once grew sympatrically in the eastern Wairarapa. de Lange (2016) has shown that these herbarium specimens are the result of accidental mixing of unmounted Thomas Kirk, North Island (S. felix) and Donald Petrie, South Island (S. laxa) specimens, and mislabelling by Thomas Cheeseman and, possibly, Victor Zotov, rather than genuine North Island wild occurrences of S. laxa. Simplicia laxa is currently known from one site near Karamea, North-West Nelson (Honeycomb Cave) and otherwise from 10 sites in Northern and Central Otago (Smissen et al. 2011). This disjunct distribution is unlikely to be natural, however, it more likely reflects the loss of interconnecting habitat as well as the difficulty of recognising this species in the field.

Smissen et al. (2011) showed that Simplicia laxa is more closely related to S. felix than it is to S. buchananii. From Simplicia felix, S. laxa can be distinguished by the culm internodes which are shorter than the subtending leaf sheaths and usually hairy (sometimes glabrous); and by the less strongly ribbed, glossy light brown to amber basal sheaths, whose ribs are pubescent (hairs 0.20–0.30 mm long). The mid-stem and upper-stem leaf sheaths of S. laxa are less prominently ribbed than those of S. felix and the ribs and, usually the interstices are hairy. The adaxial leaf surface ribs of S. laxa are hairy (abaxially glabrous), while the leaf margin is mostly smooth, though sometimes irregularly hairy or finely scabrid. The leaves of S. laxa are also wider than those of S. felix (2.8–3.6 mm wide cf. 1.0–3.0 mm wide in S. felix). However, in cultivation the leaves of both species can get up to 4.0 mm wide. Although the inflorescences of S. laxa and S. felix are similar, those of S. laxa are larger (up to 150 mm rather than 80 mm long), and the branches are antrorsely hairy rather than scabrid. Although the lemma of both species overlap in range, those of S. laxa are longer (2.8–3.4 mm long) than those of S. felix (2.0–3.0 mm long) and minutely pubescent rather than scabrid. The rachilla prolongation of S. laxa is narrowly lanceolate, 1.25–1.30 mm long and with the margins minutely ciliate, while that of S. felix is filiform, 0.8 mm long; bearing sparse cilia only near the apex. Other differences are given in Table 2.

Because of the lax, decumbent trailing growth habit, and loose linear to pyramidal inflorescences Simplicia laxa is easily distinguished in the field from the shortly tufted S. buchananii whose inflorescences are erect and whose inflorescence branches are held tightly appressed to the rhacis (Zotov 1971; Edgar and Connor 2010; de Lange et al. 2010). Other differences are provided here in the key to the species and under Table 2.

Much of what has been written about Simplicia laxa (Johnson 1995; de Lange et al. 2010) we now believe is based on observations made of remnant populations persisting in possibly suboptimal habitats (rock overhangs, rock crevices, river gorges) within locations that had once been forested. Nevertheless, the North-West Nelson, Honeycomb Cave population, which occurs in dense lowland forest, is still confined to a cave entrance and the species has yet to be found within the surrounding forest. It seems likely that Simplicia laxa is a species of deeply shaded habitats, which may, like S. felix also occur in forested situations. Further survey is needed. In the interim, all of the extant Simplicia laxa populations occur on base-rich substrates, chlorite schist and limestone, and in having this in common with the other two species it is unlikely that it will be found on less fertile substrates.

Simplicia laxa was assessed as ‘Threatened / Nationally Critical’ qualified ‘CD’ (Conservation Dependent), ‘Sp’ (Sparse) by de Lange et al. (2013). That assessment included plants described here as Simplicia felix. With the recircumscription of S. laxa the species remains appropriate assessed as ‘Nationally Critical’. Currently there are < 15 populations known, and several of these are in decline, and very few are substantial in size. Many occur on private land without direct conservation management or in places subject to ongoing habitat deterioration through invasive weed pressure and habitat loss. The qualifiers however need adjustment. Because the species is managed in a number of sites it is appropriate to retain the qualifier ‘CD’, as ceasing management would have a serious impact on the survival of the species. It is debatable whether Simplicia laxa is truly biologically sparse. It is sparsely distributed but this is more likely an artefact of past habitat loss leaving highly fragmented, disjunct ‘remnant’ populations rather than any natural pattern of distribution or species biology. We recommend that ‘Sp’ be removed from the conservation assessment for this species. The seemingly peculiar North-West Nelson, Honeycomb Cave outlier suggests that Simplicia laxa should be looked for throughout the South Island rather than, as it currently has, only in the Central and Eastern Otago Region. Also, it is now evident that we lack trend data for the species, though the overall impression is that many populations are in decline. For these reasons, we recommend that the species be qualified ‘DP’ (Data Poor) be added to the species conservation status.

Differs from Simplicia laxa by dark brown, prominently ribbed leaf sheaths; mostly glabrous, strongly ribbed mid-stem to upper-stem leaf sheaths; longer culm internodes; narrower, glabrous (sometimes with the adaxial ribs finely scabrid) leaves; shorter panicles (up to 80 mm long) with scabrid branches; minutely scabrid lemma and smaller filiform rachilla prolongation bearing cilia only at the apex.

(Fig. 7). ‘Eastern Wairarapa Ecological Region and District, Te Kanuka Farm Station, Kaumingi Stream’ P.J. de Lange 12167, J.R. Rolfe & T. Silbery, 27 Feb 2014, (AK 351325) Isotypes. CAN, CHR, F, WAIK, WELT, US

Figure 7. 

Holotype of Simplicia felix de Lange, J.R.Rolfe, Smissen & Ogle.

The epithet ‘felix’ is taken from the Latin for ‘lucky’ (N.G. Walsh, MEL pers comm., 14 January 2016) as in ‘lucky find’ in reference to the circumstances of this species’ discovery; that came about through the desire to get a name on an unremarkable little tuft of grass that was discovered fortuitously near Mangaweka, Central North Island by CCO on 29 January 2005 (Ogle 2010).

(Fig. 8). Plants forming flaccid, diffuse, often much interconnected, sprawling patches up to 1 m across. Culms 0.25–0.65 m long, green to dark brown when fresh, wiry, initially decumbent, becoming ascendant with the apices weakly erect, culm internodes 5–8, elongated, glabrous; internodes longer than subtending leaf-sheaths. Culm-nodes conspicuously swollen when fresh, dark green-brown to brown-black 0.15–0.25 mm long, rooting freely on contact with ground. Basal leaf-sheaths dull dark brown, membranous, strongly ribbed, usually abaxially pubescent (sometimes glabrous) on ribs, hairs 0.10–0.15 mm long, patent to retrorse; mid stem and upper leaf-sheaths pale-green to green, membranous, strongly ribbed, glabrous (rarely abaxially ribs finely pubescent toward sheath apex). Ligule 2.0–2.6 mm, membranous, lanceolate, apex entire, or deeply lacerate; glabrous, or with both surfaces hairy; hairs 0.15–0.18 mm long. Leaf-blade (20–)40(–60) × (1.0–)1.2–2.4(–3.0) mm, yellow-green to dark green, flat, narrow linear-lanceolate, finely ribbed, ribs smooth (sometimes minutely scabrid); margins minutely scabrid. Panicle 20–40(–80) mm long, linear to ± pyramidal, usually with basal branch or branch pair reflexed (often unevenly so); rachis glabrous (sometimes bearing a few minute prickle-teeth), branches 20–30 mm long, scabrid, binate, initially contracted but as inflorescences mature, spreading to reflexed, devoid of spikelets in lower half to two-thirds; pedicels appressed to branchlets, 0.20–0.25(0.30) mm long, finely pubescent. Spikelets 2.7–3.0 mm, 1-flowered, lanceolate, light green. Glumes pale green (± hyaline), glabrous, ovate-lanceolate to ovate, acute, 1-nerved, nerve sometimes extending beyond apex as a minute mucro, margins initially entire, becoming erose near apex, very sparsely ciliate in upper third; lower glume 0.5–0.6 mm, upper glume 0.75–0.8(–0.9) mm. Lemma 2.0–2.8 (–3.0) mm, light green to cream, ovate-lanceolate to lanceolate, acute, apex mucronate (mucro 0.1 mm long), 5-nerved, the inner 3 nerves conspicuous, the outer less prominent; nerves bearing evenly spaced minute (0.02–0.03 mm long), antrorse, appressed prickle-teeth, interstices usually densely (sometimes sparsely) covered with minute antrorse prickle-teeth. Palea 2.0–2.8 mm, lanceolate, green to purple-green, 1–2-nerved, nerves bearing evenly spaced minute prickle (0.02–0.03 mm long) teeth, interstices usually glabrous, sometimes sparsely covered with minute prickle-teeth. Rachilla prolongation 0.8 mm, filiform, hyaline, glabrous except for sparse cilia cresting prolongation apex. Stamens 3. Filaments 0.6–0.9 mm long, hyaline. Anthers 1.0–1.2 mm, yellow. Ovary narrowly ovoid to weakly trigonous 1.0 mm long, pale green, glabrous; styles apical, 1.0–1.2 mm, hyaline; stigmas plumose, white. Caryopsis 1.2–1.4(–1.5) mm long, laterally compressed, pale orange to orange-brown when mature. Chromosome number: 2n = 28 (Murray et al. 2005, P.J. de Lange 5897, AK 285424—as Simplicia laxa)

Figure 8. 

Simplicia felix. A habitat, Te Kanuka Farm Station, Upper Kaumingi Stream east Wairarapa, North Island, New Zealand B growth habit and inflorescence C culm, leaf base, sheath and ligule D spikelet showing reduced glumes and lemma (images: J.R. Rolfe)

New Zealand, North Island: Rangitikei Ecological Region and District, North of Taihape, north of Paengaroa Road and east of State Highway One, Ngawaka Stream, ‘Stevies Bush’, P.J. de Lange 7834 & C.C.Ogle, 29 Feb 2008, AK 304807 (Duplicates: CHR, US); Rangitikei Ecological Region and District, North of Taihape, south of Paengaroa Road and east of State Highway One, C.C. Ogle 4955, 17 Feb 2006, AK 295628; Rangitikei Ecological Region and District, North of Taihape, south of Paengaroa Road and east of State Highway One, C.C. Ogle 4954, 17 Feb 2006, AK 295627; Rangitikei Ecological Region and District, North of Taihape, south of Paengaroa Road and east of State Highway One, ‘Campbells Bush’ P.J. de Lange 7832 & C.C. Ogle, 29 Feb 2008, AK 304805; Taihape, Oraukura Stream, C.C. Ogle 5625, 6 Apr 2008, AK 306012; Rangitikei Ecological Region and District, Taihape Scenic Reserve, Hautapu, P.J. de Lange 7833, C.C. Ogle & V. McGlynn, 28 Feb 2008, AK 304806; Rangitikei Ecological Region and District, Taihape Scenic Reserve, Hautapu, C.C. Ogle 4958 & V. McGlynn, 7 Mar 2006, AK 297357; Rangitikei Ecological Region and District, Rangitikei, Kawhatau Valley, Toetoe Road, C.C. Ogle 4893, V. McGlynn & G. La Cock, 13 Dec 2005, AK 297353; Rangitikei Ecological Region and District, Rangitikei, Kawhatau Valley, Toetoe Road, P.J. de Lange 7831, C.C. Ogle & V. McGlynn, 28 Feb 2008, AK 304804; Rangitikei Ecological Region and District, Rangitikei, Kawhatau River, Toetoe Road, ‘Ben Moi’ farm, C.C. Ogle 4734, 29 Jan 2005, AK 289755 (Duplicate: CHR); Eastern Wairarapa Ecological Region and District, Te Kanuka Farm Station, Swamp Ridge Covenant, P.J. de Lange 12165, J.R. Rolfe & T. Silbery, 27 Feb 2014, AK 351320 (Duplicates lodged in: CHR.WELT, US); Eastern Wairarapa Ecological Region and District, Te Kanuka Farm Station, Upper Kaumingi Stream, P.J. de Lange 12168, J.R. Rolfe & T. Silbery, 27 Feb 2014, AK 351330 (Duplicates lodged in: CAN,WELT, US); Wairarapa, Ruamahanga, T. Kirk s.n., n.d., WELT SP043016; Ruamahanga Valley, T. Kirk s.n., 26 Jan 1880, WELT SP043022; Eastern Wairarapa Ecological Region and District, Admiral Road, Wainuoru River, Te Kowhai, Moetapu Bush, P.J. de Lange 12160, J.R. Rolfe & T. Silbery, 26 Feb 2014, AK 351290 (Duplicates: WELT, US); Eastern Wairarapa, Longbush, Tawhiriwaimanuka Stream. Ahipaku QE II Covenant, J. R. Rolfe 15017, 9 Dec 2015, AK 360429 (Duplicate: WELT). South Island: South-East of Duntroon, Prydes Gully Road (Ngapara, The Knolls), B.P.J. Molloy s.n., 18 Dec 1991, CHR 616708; Duntroon Ecological District, Ngapara, The Knolls, P.J. de Lange 1340 & B.P.J. Molloy, 7 May 1992, AK 208577 (Duplicates: CHR, WAIK, WELT). Cultivated: Ex. Cult., Rangitikei Ecological Region and District, Rangitikei, Kawhatau Valley, Toetoe Road, P.J. de Lange 6791, 30 Nov 2006, AK 297927; Ex. Cult., Rangitikei Ecological Region and District, Rangitikei, Kawhatau Valley, Toetoe Road, P.J. de Lange 6824, 23 Dec 2006, AK 298065; Ex. Cult., Duntroon Ecological District, Ngapara, The Knolls, P.J. de Lange 5897, 23 Feb 2004, AK 285424; Ex. Cult., Duntroon Ecological District, Ngapara, The Knolls, P.J. de Lange 6103, 3 Sep 2004, AK 288070.

(Fig. 1). Simplicia felix has so far been collected from the North and South Islands, from the current northern limit at Ngawaka Stream, near Taihape, North Island to Ngapara, North Otago, South Island. In the North Island the species has been found in two broad geographic areas, around Taihape–Mangaweka, and in the eastern Wairarapa. In the South Island, Simplicia felix is so far known only from the one location at Ngapara.

Genetically and morphologically Simplicia felix is more closely related to S. laxa than it is to S. buchananii. From Simplicia laxa it can be distinguished by the culm internodes which are longer than the subtending leaf sheaths and consistently glabrous; and by the strongly ribbed, dull dark brown basal sheaths, whose ribs are glabrous or pubescent (if pubescent then with the hairs 0.10–0.15 mm long). The mid-stem and upper-stem leaf sheaths of S. felix are strongly ribbed and usually glabrous (occasionally the ribs are finely pubescent towards the sheath apex). The leaf surfaces and margins of S. felix are mostly smooth though the ribs and leaf margins may be minutely scabrid. As a rule, the leaves of S. felix are also shorter (up to 60 mm in S. felix, 200 mm in S. laxa) and narrower than those of S. laxa (1.0–3.0 mm long cf. 2.8–3.6 mm long in S. laxa). However, in cultivation the leaves of both species can get up to 4.0 mm wide. Although the inflorescences of S. laxa and S. felix are similar, those of S. felix are smaller (up to 80 mm long rather than 150 mm long), and the branches are scabrid rather than antrorsely hairy. Although the lemma of both species overlap in range, those of S. felix tend to be shorter (2.0–3.0 mm long) than those of S. laxa (2.8–3.4 mm long) and minutely scabrid rather than pubescent. The rachilla prolongation of S. laxa is narrowly lanceolate, 1.25–1.30 mm long and with the margins minutely ciliate, while that of S. felix is filiform, 0.8 mm long and bearing sparse cilia only near the apex. Other differences are given in Table 2.

Simplicia felix was initially confused with S. buchananii (see Ogle 2010; Smissen et al. 2011) mostly because the culm internodes of both species are glabrous; they have superficially similar strongly-ribbed, often glabrous leaf-sheaths, similar smooth or finely scabrid leaves, and minutely scabrid lemma. Despite these similarities, Simplicia felix is not closely allied to S. buchananii from which it is readily distinguished by the lax, sprawling, rather than erect culms; linear-pyramidal rather than linear inflorescences with binate branching, and by the lower branch or branches usually reflexed rather than appressed to the rachis. The pedicels of S. felix are also pubescent rather than glabrous (rarely minutely scabrid).

With the exception of the Ngapara population which grows within a limestone overhang, Simplicia felix has only been collected from central and eastern North Island lowland to lower montane, often riparian, seasonally dry (drought prone), Podocarp forests overlying base-rich substrates such as limestone, calcareous mudstone and siltstone. In these areas plants have been found only in lightly shaded situations within forest remnants that have been lightly under-grazed by cattle or sheep (Ogle 2010; de Lange et al. 2014). The reduced competition from other grasses and herbs that grazing causes, seems crucial to this species’ survival (de Lange et al. 2014) as, in some locations where S. felix had been found, portions of the same forest that had been fenced to exclude livestock did not have Simplicia). In the Taihape–Rangitikei area, Ogle (2010) noted a close association with a range of other indigenous grasses and herbs, most notably Echinopogon ovatus, Poa imbecilla, P. matthewsii, Cardamine debilis agg., Oxalis exilis. In the Eastern Wairarapa the same species along with Arthropodium candidum, Australina pusilla subsp. pusilla, Stellaria parviflora and the mosses Camptochaete angustata, Echinodium hispidum and Plagiomnium novae-zelandiae were key associates of Simplicia felix (P. J. de Lange unpubl. data). Further survey of similar forest remnants with ground covers dominated by these species is, we believe, likely to locate further populations.

The Ngapara site, as S. laxa, was described in some detail by Johnson (1995). By comparison with the North Island sites it is anomalous and it seems likely that Simplicia persists there because the rock overhang affords some shade and protection from competing plants. Within the rock overhang Simplicia felix grows with Poa imbecilla, P. matthewsii, Chenopodium allanii and an unnamed member of the Cardamine corymbosa complex.

Simplicia felix occupies a very small area of only a few square metres wherever it occurs. It appears to have quite specific light requirements and tolerates only limited competition from other ground-cover species. The healthiest populations occur at sites where competition is reduced by grazing mammals such as cattle and sheep. This poses a quandary for conservation managers because, whilst grazing apparently benefits S. felix, it will ultimately lead to the collapse of the forest canopy that provides the level of shade that is also necessary for S. felix to survive. Collectively, the area of the sites where S. felix occurs amounts to considerably less than 1 ha. Therefore, S. felix meets the criteria to be assessed Threatened—Nationally Critical B2 using the New Zealand Threat Classification System (Townsend et al. 2008). We also recommend that the qualifiers Data Poor (‘DP’) and Range Restricted (‘RR’) be appended to the assessment—‘DP’ because there are no population trend data available and because several areas of possibly suitable habitat in the Rangitikei and Eastern Wairarapa have not been surveyed for the presence of S. felix; ‘RR’ because its habitat requirements are apparently very narrow.