Viola pachysoma M. Sheader & J.M. Watson, 2018

Watson, John M., Flores, Ana R., Sheader, Martin & Sheader, Anna-Liisa, 2018, Viola pachysoma (Violaceae), a new name for a rosulate species endemic to the Andes of Argentinian Patagonia, Phytotaxa 382 (1), pp. 113-124 : 114-116

Viola pachysoma M. Sheader & J.M. Watson , nom. nov. ( figs. 2A–D , 3A–C , 5A–C ).

Basionym: — Viola copahuensis M. Sheader & A. Sheader (2014a: 210) , nom. illeg., nom. superfl. Type: — ARGENTINA. Neuquén

Province, Ñorquin Department: Volcán Copahue, above Termas de Copahue, 37º49.2’S 71º06.2’W, 2065m, 6 December 2010, leg.

M. & A. Sheader, MAS 10121 (holotype: herb Sheader; isotype: BCRU). = Viola columnaris sensu auctt. non Skottsberg (1916: 261). = Viola petraea sensu auctt. non W. Becker (1925: 354). = Viola × blaxlandiae sensu auctt. non J.M. Watson & A.R. Flores (2012: 370), pro parte. ≡ Viola caviahuensis M. Sheader & A. Sheader (2014b: 245) nom. illeg., nom. superfl.

Supplemetary diagnosis:— Viola pachysoma is closest to V. columnaris , from which it may be told by its differently shaped and glabrous corolla and significantly disjunct distribution.

Description:— Life form perennial , rosulate, glabrous, evergreen hemicryptophyte. Rootstock axial, to ca. 35 cm long × 2 cm dia. at junction with caudex, stout, ligneous above. Caudex to ca. 10 cm, simple or branched, enveloped below living foliage with vestiges of dead vegetation. Plant solitary to forming dense cushions, rarely of many rosettes. Rosette ca. 2.5–6.5 cm dia. × 2–7.5(–9) cm high, densely imbricate to base, frequently columnar, usually cryptic, but at times green, somewhat depressed towards centre of face. Leaves spathulate, ca. 1–2.5 cm when mature, arranged in distinct spirals, estipulate; pseudopetioles 4.6–14 mm, plane, more or less thick and fleshy; lamina 5.4–6.5 × 5–6.5 mm, entire, broadly ovate to suborbicular to rarely wider than long, leathery-succulent, minutely apiculate at tip, margin 0.5 mm wide, thin-cartilaginous, pale-translucent. Anthesis more or less simultaneous. Flowers ca. 1 cm high × 1 cm wide, axial, solitary, forming dense ring around, and somewhat included within, upper circumference of rosette. Peduncles ca. 7 mm, somewhat shorter than leaves; bracteoles 5.5–6.2 mm, basal, linear with acute-subulate apex, hyaline. Calyx 6–7.8 mm; sepals unequal, triangular, acuminate. Corolla glabrous, white to pale whitish violet, with rare pale yellow form known ; more or less veined violet on inferior longitudinal half of lateral petals, and as central line or lines on superior petals, these rarely unmarked; venation more pronouced and extensive on lowermost petal, this yellow at base; reverse of all petals more heavily veined violet; superior petals 5.8–9.5 × 2–3.1 mm, linear, apex rounded to rounded-obtuse; lateral petals 7.5–10.3 × 2.9–4.6 mm, apex obovate, rounded to obliquely subtruncate; inferior petal 8–11.2 × 7.8–9 mm, obtriangular, emarginate to subtruncate, with minute point in apical sinus or at apex; spur 1.5–2 × 1.8–2.1 mm, stoutly cylidrical, retuse. Androecium and gynoecium, exserted, readily visible; anthers ca. 1.2–1.5 mm, lower pair with filiform nectar spurs; connectives equal in length to anthers, orange; style geniculate, clavate; style crest short, lateral, retrorse-uncinate, rarely patent lobe-arm either side of style head, these conjoined and sometimes with minute central apical projection. Fruit 3.5–4 mm, orbicular, tri-valved capsule; seeds not seen. (Descriptio typo M. & A. Sheader emend. J.M. Watson & A.R. Flores.)

Note:— It is sometimes possible to observe evident layers of annual growth in older, conspicuously columnar individuals ( fig. 2A ).

Etymology:— A notable characteristic of the species is the frequently robust structure of its columnar rosettes. We have reflected this in its replacement epithet, pachysoma , which is Greek for ‘stout-bodied’.

Distribution and habitat:— A narrow endemic of Argentina, known mainly from the general sector of Volcán Copahue and Caviahue, where it forms a number of scattered and substantial populations from as low as the Salto del Agrio at ca. 1600 m to just over 2000 m in the subnival zone. Other named sites are on the slopes of Volcán Copahue itself; between Copahué and the Laguna Las Mellizas; and the Cordon del Cajon Chico. Another well separated population is known from near Primeros Pinos about 130 km to the south, also in Neuquén province (Sheader & Sheader 2014a). V. pachysoma very probably occurs on the immediately adjacent and less accessible western, Chilean flanks of the Copahue vocano, and should be looked for there. It inhabits ashfields, as well as stony levels and shallow slopes, and also occurs in crevices or among rocks, all of volcanic origin. It commonly grows in isolation or with scattered dwarf vegetation of Patagonian or high Andean steppe formations.

Phenology: — Flowering from the beginning of December to January, with fruits maturing between mid-January and the end of February.

Considered conservation status:— The main distribution of V. pachysoma is situated within the Área Natural Protegida Copahue, a provincial nature reserve. It was founded in 1937 and established by law in its present form in 1963 ( ANP 2018). The terrain covered is of value both for tourism and as an area of outstanding natural beauty and interest. The reserve includes the Argentinian exposures of the Copahue volcano. Although this dominant geological feature is active, the rich, established flora of its immediate environs indicates that it apparently does not pose a natural threat. V. pachysoma is also not uncommon within its range. Despite lack of any environmental protection for the Primeros Pinos sector, these factors suggest that the species does qualify as potentially vulnerable due to its limited distribution, but nevertheless is under no immediate threat.

Figures

FIGURE 2. Viola pachysoma. A. Individual cryptic-coloured plant as solitary, columnar rosette.Argentina, Neuquén Province, Copahue. 13 January 2010. (Photo: Kees Jan van Zwienen). B. Lateral view of flower showing spur. Argentina, Neuquén Province, Primeros Pinos. 4 December 2013. (Photo: Martin & Anna-Liisa Sheader). C. Individual plant of F.& W. 8271 with various subdepressed adjoined rosettes.Argentina, Neuquén Province, Copahue.8 December 1994.(Photo: John Watson). D. Superior view of flower showing style crest. Argentina, Neuquén Province, Primeros Pinos. 4 December 2013. (Photo - Martin & Anna-Liisa Sheader).

FIGURE 3. Viola pachysoma. A. Columnar, multi-rosetted, uncommon yellow-flowered form. Argentina, Neuquén Province, Copahue. 21 December 2002. (Photo:Ana Flores). B. Fasciated individual.Argentina, Neuquén Province, Copahue. 13 January 2010. (Photo: Kees Jan van Zwienen). C. Green-coloured, solitary, columnar, unirosulate form. Argentina, Neuquén Province, Argentina, Neuquén Province, Copahue. 13 January 2010. (Photo: Kees Jan van Zwienen).

FIGURE 5. A. Viola pachysoma. Columnar unirosulate plant. Argentina, Neuquén Province, Copahue. 13 January 2010. (Photo: Kees Jan van Zwienen). B. Viola pachysoma. Frontal view of flower. Argentina, Neuquén Province, Copahue. 13 January 2010. (Photo: Kees Jan van Zwienen). C. Viola pachysoma. An entire unirosulate plant unearthed, showing axial rootstock. Argentina, Neuquén Province, Primeros Pinos. 4 December 2013.(Photo: Martin &Anna-Liisa Sheader). D. Viola dasyphylla. Small plant.Argentina, Neuquén Province, Cerro Colorado. 19 December 2007. (Photo: Ana Flores).