Simplicia laxa Kirk, T.N.Z.I. 29: 497, t.44 (1897)

de Lange, Peter J., Smissen, Rob D., Rolfe, Jeremy R. & Ogle, Colin C., 2016, Systematics of Simplicia Kirk (Poaceae, Agrostidinae) - an endemic, threatened New Zealand grass genus, PhytoKeys 75, pp. 119-144 : 130-134

Simplicia laxa Kirk, T.N.Z.I. 29: 497, t.44 (1897)

≡ Simplicia laxa Kirk var. laxa (autonym, Zotov T.R.S.N.Z. 73: 236 (1943))

Lectotype.

' Waikouaiti, Otago’ D. Petrie s.n., n.d. (WELT SP043017 !) (fide Zotov 1971)

Isolectotype.

' Waikouaiti, Otago, D.Petrie s.n., n.d. (WELT SP043021 !) (fide Zotov 1971)

Etymology.

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).

Description

(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: 2 n = 28 ( Zotov 1971, I.M. Ritchie s.n., CHR 202752)

Specimens seen.

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 SP043020 A, WELT SP043020 B, WELT SP043020 C, 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, 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) .

Distribution

(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 Simplicia felix and Simplicia 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 ( Simplicia felix ) and Donald Petrie, South Island ( Simplicia laxa ) specimens, and mislabelling by Thomas Cheeseman and, possibly, Victor Zotov, rather than genuine North Island wild occurrences of Simplicia 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.

Recognition.

Smissen et al. (2011) showed that Simplicia laxa is more closely related to Simplicia felix than it is to Simplicia buchananii . From Simplicia felix , Simplicia 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 Simplicia laxa are less prominently ribbed than those of Simplicia felix and the ribs and, usually the interstices are hairy. The adaxial leaf surface ribs of Simplicia laxa are hairy (abaxially glabrous), while the leaf margin is mostly smooth, though sometimes irregularly hairy or finely scabrid. The leaves of Simplicia laxa are also wider than those of Simplicia felix (2.8-3.6 mm wide cf. 1.0-3.0 mm wide in Simplicia felix ). However, in cultivation the leaves of both species can get up to 4.0 mm wide. Although the inflorescences of Simplicia laxa and Simplicia felix are similar, those of Simplicia 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 Simplicia laxa are longer (2.8-3.4 mm long) than those of Simplicia felix (2.0-3.0 mm long) and minutely pubescent rather than scabrid. The rachilla prolongation of Simplicia laxa is narrowly lanceolate, 1.25-1.30 mm long and with the margins minutely ciliate, while that of Simplicia 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 Simplicia 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 .

Ecology.

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 Simplicia 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.

Conservation status.

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 Simplicia 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.

Figures

Figure 1. Distribution of Simplicia species and showing locations discussed in text.

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)