Xyris desquamatus J.R. Morel & Munzinger, 2021

Morel, Jérémie & Munzinger, Jérôme, 2021, Novitates neocaledonicae. XIII. Taxonomy and nomenclature of the genus Xyris (Xyridaceae, Poales) in New Caledonia, with description of a new species, Phytotaxa 502 (3), pp. 219-229 : 220-225

Xyris desquamatus J.R. Morel & Munzinger , sp. nov. ( Figs. 1 , 2 )

Type :— NEW CALEDONIA. Southern end of plaine des lacs, road le Carénage, elev. 150 m, 20 August 1956, H.S. MacKee 5056 (holotype: P! [P01760130], isotypes: L [L1430190] (image seen), K [K000481266] (image seen)) .

Diagnosis —Differs from X. pancheri in having junciform and terete leaves (13–50 x 0.1–0.3 cm) (versus linear and elliptic in cross-section), which peal away and become ribbed at senescence (versus remain entire), staminodes reduced to filaments (versus staminodes developed and densely feathery), presence of palisade parenchyma and collenchyma (versus absence) and a thickening of the medullary parenchyma (versus no thickening) before its disintegration to form a thatch.

Perennial herbs, scapose and cespitose, clumps to 30 cm square. Leaves (12.7–)23.6–36.5(–50.4) cm long, spiral, erect, twisted, green, glabrous, sheaths 5.4–10 × 0.7–1 cm, widely dilated towards the base, dark and glossy brown, smooth, margin brown-hyaline to golden, glabrous, blade junciform, terete, highly variable in length, from 0.3 to 41 cm long × (1–)1.8–2.1(–2.9) mm in diameter. Ligule absent. Peduncle erect, twisted, elliptic in cross-section, smooth, green, glabrous, (26.4–)30.6–53.6(–83.4) cm long, (1.5–)1.7–2.1(–3.5) mm in diameter. Leaves and peduncles brownish at senescence, then peel away (corresponding to epiderm, palissade parenchyma and collenchyma) and become ribbed (corresponding to prominence of vascular bundles). Spikes (8.3–)14.2–18.1(–41) × (5.6–)10.7–13.6(– 18) mm, with few flowers, ellipsoid to ovoid. Basal sterile bracts 2–3 × 2 mm, ovate, ecarinate, forming a continuum with fertile bracts 10–13 × 5.6–6.7 mm, yellowish, oblong, slightly curved, bordered by a translucent membranous margin, carinate apically, apex rounded (difficult to see on isolated and dehydrated bracts), glabrous, distinct reddish triangular dorsal region in vivo (absent on herbarium specimens) with some ornaments, each ornament white and circular, (0.3–)0.4–0.45(–0.5) mm in diameter. Flowers with lateral sepals 6.3–8.2 × 0.9–1.1 mm, brown adaxially, included, bordered with translucent yellowish margins, two dark brown dorsal longitudinal lines topped with gradually attenuating brownish trichomes, free, equal and linear. Petals yellow, glabrous, clawed, 14–16 mm long, lobes 4.7–6.2 × 3.8–4 mm, obovate, margins crenate. Androecium yellow, glabrous, anthers linear, 2.3–2.7 mm long, pressed against the blades of the petals and barely protrude, filaments adnate along the entire length of the claw, free for 1.4–1.7 mm long, staminodes reduced to filaments. Gynoecium yellow, glabrous, style 5–5.5 mm long, branches ca. 2.5 mm long, stigma dilated at the apex. Ovary obovoid, glabrous, 2–4 mm long, ca. 1 mm in diameter, glabrous, brownish, trilocular, axile placentation. Capsule globose, 4.5 × 2–3 mm, brown. Seeds ellipsoid, sometimes prismatic, 1–1.3 × 0.4–0.6 mm, brownish with irregular protuberances.

Anatomy:—Anatomically ( Fig. 3 ), the leaves differ from the other two species present in New Caledonia by a strong cutinization inward the epidermal cells, presence of a palisade parenchyma, collenchyma and a progressive thickening of the medullary parenchyma (pith) prior to its disintegration, what create a thatch.

Distribution and Ecology:— Xyris desquamatus is restricted to the southern province of New Caledonia, on ultramafic substrates (ironcrust, peridotites, lateritic alluviums or colluviums), over an altitude ranging from 150 to 550 m ( Fig. 4 ). It is present in tufts scattered in open swampy vegetation with Cyperaceae and Juncaceae (MacKee 5056, Brown 92/231), very open dry maquis (MacKee 43247), hydromorphic maquis (Dagostini 1343), riparian maquis (Dagostini & Rigault 544) or river bank, amongst gymnosperms and stunted maquis vegetation with epacrids and Acacia (Brown 92/210). The population found at the highest altitude (540-550 m, Gâteblé et al. 1070 & 1071) was found in a scrubland resembling high altitude maquis (Gâteblé pers. comm.).

Photos of the plant in the field seem to show that the stigmas are mature while the stamens are not yet at anthesis, suggesting that the species may be protogynous.

Etymology:—The epithet desquamatus refers to the peeling of leaves and stipes at senescence.

Discussion:— Conert (1965) confused Xyris desquamatus with X. pancheri . These two species coexist in open vegetation environments. Of the 129 specimens studied during the revision of the genus ( Morel et al. 2021), only 18 belong to the species X. desquamatus . This species has a terete stipe which distinguishes them from X. neocaledonica . Nevertheless we can differentiate them by distinct leaf forms: jonciform (terete) in the case in X. desquamatus and linear (elliptic in cross-section) in X. pancheri . In addition, only the leaves and stipes of X. desquamatus can peel and become ribbed. Furthermore, the bracts of the spike of X. desquamatus are more rigid with a finer membranous margin and a constant and prominent carina than in X. pancheri . Finally, the flower of X. desquamatus has only staminodes reduced to filaments while the staminodes of X. pancheri are feathery ( Fig. 5 ).

It is relevant to note that Guillaumin (1956: 133) rightly identified MacKee 2609 as X. pancheri and indicated MacKee 2365 as a new species (indeed this specimen is X. desquamatus ). Conert probably wanted to dedicate this species to Guillaumin but he inverted his identifications and described X. guillauminii for the taxa already described as X. pancheri , and leaving the new species, X. desquamatus , undescribed ( Morel et al. 2021).

Conservation status:—The plant is known from eleven subpopulations, only one of which is in a protected area: “La réserve naturelle du Pic du Pin”, while five of them are included in mining concessions. The calculated EOO is 189 km 2 and the AOO is 48 km 2. According to MacKee 5056 [P01760130] and MacKee 43247 [P01766991] 30 years apart (1956 and 1986), X. desquamatus is generally infrequent, sometimes common but in small areas. Some subpopulations may be threatened by bushfires and/or introduced browsers, in addition to mining activity. We assign Xyris desquamatus a preliminary status of Vulnerable (VU B1ab(iii,v)+2ab(iii,v)).

Additional specimens examined (Paratypes):— NEW CALEDONIA. Province Sud: Baie de Prony, Sep 1868, B. Balansa 665 (P01760139, P01760140, P01760141); Chutes de la Madeleine, 22°13’10”S, 166°51’39”S, 7 Nov 1992, Brown 92/210 ( NSW262218 ); Road between Nouméa and Yaté, 8.3 km E of turnoff to Chutes de la Madeleine , 22°10’03”S, 166°54’00”E, 10 Nov 1992, Brown 92/231 ( NSW262220 ); Goro-nickel , Kwé Est [-22,3064; 166,9221333], 17 Oct 2002, G. Dagostini & F. Rigault 544 ( NOU046841 ); Rivière des Lacs ( La Madeleine ) en amont des chutes [- 22,1928016; 166,8732611], 20 Sep 2007, G. Dagostini, F. Rigault, L. Barrabé & W. Nigote 1343 ( NOU023766 ); Plaine des lacs: Grand Lac [-22,268464; 166,914619], 15 Sep 1981, P. Endress 6235 (Z-000175352); Yaté , Sommet du Mont Gouemba , 540 m alt., 22°10’42.40”S, 166°56’21.69”E, 29 Nov 2018, G. Gâteblé, Y. Isagi & Y. Suyama 1070 ( MO, MPU, NOU107278 , NOU107279 , NSW, P); Yaté , Sommet du Mont Gouemba, 540 m alt., 22°10’42.40”S, 166°56’21.69”E, 29 Nov 2018, G. Gâteblé, Y. Isagi & Y. Suyama 1071 ( MO, MPU, NOU107280 ); Pic du Pin [22°14’49’’S; 166°48’48’’E], 1 Apr 1951, A. Guillaumin & M. Baumann-Bodenheim 11947 (P01679382); Open seepage slope bordering the Anna- Madeleine River . Nouméa - Yaté road about 42 km. ENE of Noumea [-22,1675, 166,8666667], 23 Nov. 1979, Hartley 15055 ( CANB289172.1 , NOU046840 ); Col de Yaté , 300 m alt. [22°10’19’’S; 166°54’15’’E], 1 Mar 1992, H. Koyama & H. Setoguchi 8204 (P01760146); Plaine des lacs, on road to Le Carenage, 150 m [22°17’25’’S; 166°50’5’’E], 8 Apr 1955, H.S. MacKee 2365 (L1430188); Grand Lac, 250 m [-22,27277778, 166,9008333], 30 Sept 1984, MacKee 42273 ( NOU046832 , NSW, P01767010 ); Yaté , 350 m alt. [22°9’21’’S; 166°53’48’’E], 31 Aug 1986, H. S. MacKee 43247 ( NOU046835 , NSW, P01766991 ); Lac en 8 [22°16’17’’S; 166°52’35’’E], 13 Oct 1976, P. Morat & B. Suprin 5141 ( NOU046836 , P01766979); Plaine des lacs, [1889], M. Raoul s.n. (P01760152); Bords du lac Arnaud [22°6’40’’S; 166°48’51’’E], 1855/1860, E. Vieillard 1410 (P01766983) .

Figures

FIGURE 1.—Xyris desquamatus J.R.Morel & Munzinger, A Habit (MacKee 5056, holotype [P01760130]) B Leaf tip with details of the surface (Balansa 665) C Fertile bract, dorsal view (Dagostini & Rigault 544) D Sepal (MacKee 42273) E Spike (Based on a picture in the field of the collection Gâteblé et al. 1070) F Flower (Dagostini & Rigault 544) G Gynoecium (Dagostini & Rigault 544) H Petal and stamen (Dagostini & Rigault 544) I Seed (Dagostini & Rigault 544). Drawings by Jérémie Morel.

FIGURE 2.—Xyris desquamatus A Habit in situ B Spike C Spike with a flower in lateral view D Junciform leaves E Focus on junciform (red arrow) and desquamating leaves (red and white arrow). (Same population as Gâteblé et al. 1070 & 1071). Photos by Gildas Gâteblé (A–E).

FIGURE 3.—Comparison of anatomical characters of the three species of Xyris of New Caledonia.Transversal cross sections of leaves (A– C, scale bars = 1000 μm), epidermis with cortical parenchyma (B1) and epidermis with palisade parenchyma (C1), medullary parenchyma (B2 & C2), cortical parenchyma (B3) and cortical collenchyma (C3), scale bars = 20 μm. A Xyris neocaledonica [NOU046858] B Xyris pancheri [P01766981] C Xyris desquamatus [P01766983] B1 X. pancheri [NOU04838] B2 X. pancheri [P01767050] B3 X. pancheri [NOU021191] C1 X. desquamatus [NOU046832] C2 X. desquamatus [P01760139] C3 X. desquamatus [P01766983].

FIGURE 4.—Distribution of Xyris on Grande Terre, New Caledonia based on herbarium specimens. X. desquamatus (black dots, type specimen indicated with a “T”), X. neocaledonica (black crosses), X. pancheri (dark grey squares with a black dot).

FIGURE 5.—Comparison between flowers of the three species of Xyris of New Caledonia. A X. desquamatus (same population as Gâteblé et al. 1070 & 1071) B X. pancheri (Gâteblé 999) C X. neocaledonica (Munzinger et al. 7689). Photos by Gildas Gâteblé (A–B) and Jérôme Munzinger (C).