Viola watsoniana, Nicola, Marcela V., Salomón, Luciana & Flores, Ana R., 2024

Nicola, Marcela V., Salomón, Luciana & Flores, Ana R., 2024, A new species of Andean rosulate Viola (subg. Neoandinium, Violaceae) endemic to the Puna of north-western Argentina, Phytotaxa 671 (3), pp. 271-283 : 274-275

Viola watsoniana A.R. Flores & Nicola, sp. nov. ( Fig. 1 ).

Type: — ARGENTINA. Jujuy: Dpto. Humahuaca, Mina Aguilar, Espinazo del Diablo, 3,660 m, 23º 13’ 02’’ S, 65º 35’ 42’’ W, 13 March 2013, F. O. Zuloaga et al. 14262 (holotype SI 118776!, isotype MU!). ( Fig. 2 ).

Diagnosis: — Similar to Viola roigii and V. xanthopotamica , but V. watsoniana presenting rosettes with leaves arranged in a looser manner (vs. rosettes with leaves arranged in a more compact and orderly manner in V. roigii and V. xanthopotamica ), upper lamina surface without a clear differentiation of secondary veins (vs. upper lamina surface with 3 or 4 secondary veins in V. roigii and V. xanthopotamica respectively), lamina margins glabrous (vs. margins ciliate in V. roigii and V. xanthopotamica ) with smoother crenations (vs. margins crenate to lobed with sharply crenations in V. roigii and V. xanthopotamica ), and margin of the style crest not entire, irregularly sinuate (vs. entire in V. roigii and V. xanthopotamica ). Viola watsoniana also differs from V. xanthopotamica by having smaller vegetative and larger reproductive structures (vs. larger vegetative and smaller reproductive structures in V. xanthopotamica ), and lower lamina surface glandular (vs. eglandular in V. xanthopotamica ).

Description: — Rosette-forming herb, probably perennial, rosette 1−3.5 cm diameter when mature, approximately hemispherical and flattened, glabrous; main stem 2−4.5 mm diameter, generally solitary, not branched, rarely bifurcated. Foliage spirally arranged and loosely imbricate; mature leaf 8−16 mm long in total, including lamina and pseudopetiole, glabrous. Lamina typically elliptic to oval, rarely ovate, 4−9 × 2−5 mm, flexible, somewhat crass; apex mainly acute (rarely obtuse); margins subcrenate to crenate with 4 to 6 pairs of smooth crenations, extremely rare entire within the same plant, thickened and curved in each crenation towards the center of the lamina, ending in each sinus with one orange circular gland; base attenuate in pseudopetiole; upper surface greenish-brown with raised reticulate venation; lower surface reddish-brown with reddish elliptic glands irregularly distributed towards the margins of the basal portion of the lamina. Pseudopetiole 4−10 × 0.5 mm, margins of the lower surface with reddish elliptic glands distributed especially towards the upper portion of the pseudopetiole in a row on each side of the central vein. Stipules present, persistent, lanceolate-triangular, ca. 5 × 1 mm, apex thinly acute, margins entire to little laciniate, with one orange elliptic gland at the junction with the pseudopetiole, base truncate. Flower ca. 10 mm high × 10 mm wide, emerging briefly from the foliage, white with yellow throat and usually with purple lines on both faces of all petals. Peduncle 5−14 mm long, glabrous. Bracteoles present, persistent, inserted towards the bottom of the peduncle, lanceolate-triangular, 3−4 mm long, margins entire to little laciniate, glabrous. All sepals green and glabrous with margins hyaline, apex acute, and basal calycine appendage rounded, short, ca. 0.3 mm; upper sepal lanceolate-triangular, 3−4 × 1 mm; lateral sepals oblong, 4 × 1 mm; lower sepals oblong-lanceolate, 3−4 × 1−2 mm. Upper petals oblong-spatulate, apex obtuse to emarginated, base slightly curved laterally, 7−8 × 3 mm, glabrous, occasionally with 1 gland of irregular shape in its upper portion. Lateral petals oblong-spatulate, apex obtuse to emarginated, base slightly curved laterally, 8−9 × 3, with a tuft of claviform white hairs towards the lower half of the petal, occasionally with 1 or 2 glands of irregular shape in its upper portion. Lower petal panduriform-obcordate, ca. 8−10 × 5−7 including spur, strongly emarginated at apex, folded at base forming a channel towards the spur, with two rows of short simple hairs at the base of the petal towards the opening of the spur; spur ca. 2 × 1.5 mm, rounded. Stamens ca. 2 mm long; apical connective appendage ca. 1 mm long, brownish; anthers ca. 1.5 mm long; basal nectariferous appendage of lower stamens filiform, ca. 1.5 mm long. Ovary ca. 1.5 mm long, glabrous; style clavate-capitate, little geniculate; style crest on the posterior face of the apex, transverse, semi-orbicular, with margin irregularly sinuate to rarely cleft, thickened; stigma frontal, rostrate, prominent, crested. Capsule ca. 5 × 4 mm; seeds 1−1.5 mm × 1 mm, brown when mature, elaiosome absent. ( Fig. 3 ).

Etymology: — We lovingly dedicate this new species to John Michael Watson (1936−2024), English botanist settled in Chile. Married to his colleague Ana R. Flores (born in 1953), they have made numerous trips to collect specimens throughout the Andes Mountains, have their own herbarium (herb. Flores & Watson), and run a botanical breeding company ( Flores & Watson Seeds). John M. Watson was a connoisseur of all the Andean flora, but he especially fell in love with the Andean rosulate violets since the 1990s. He became one of the greatest specialists of this plant group in the region, always consulted for his extensive knowledge of field and herborized plants. He described 30 taxa of Viola , published about 45 articles and books on the subject, contributing enormously to the knowledge of the genus specially for the floras of Argentina and Chile, and also of Bolivia and Peru. He summarized his knowledge in the vast monograph on subgenus Neoandinium ( Watson et al. 2021) , which contributed to complete and better understand the classification of the entire genus ( Marcussen et al. 2022). Thanks to John’s keen botanical eye, V. watsoniana could be released to science and we give it its name.

Distribution and habitat: — Viola watsoniana has been found only in its type locality ( Fig. 2 ), despite successive botanical explorations in surrounding areas. Thus, this species appears to be endemic to the mountain range Espinazo del Diablo, in the Argentinian Eastern Cordillera of the Province of Jujuy, located in north-western Argentina, in the southern portion of the Central Andes. It grows at 3,660 –3,670 m of altitude, in a colourful geological formation of sedimentary folds consisting of sandstones and shales (Aceñolaza 1968). This area corresponds to the Puna Biogeographic Province ( Cabrera & Willink 1980), a region with dry and cold climate, and exposed rocky soils. The vegetation is dominated by steppe shrubs, creeping or cushion plants, and annual species or plants with perennial underground organs that appear only during the rainy season in summer.

Phenology: — Seen in bloom in January and beginning fruiting in March.

Additional material examined (paratype): — ARGENTINA. Jujuy: Dpto. Humahuaca, Mina Aguilar, Espinazo del Diablo, 3,670 m, 23º 13’ 02’’ S, 65º 35’ 43’’ W, 16 January 2012, F.O. Zuloaga et al. 13575 (SI!).

Estimated conservation status: — So far and in spite of explorations in nearby locations, Viola watsoniana is only known from two close collections at its type locality in the mountain range Espinazo del Diablo, Province of Jujuy, in northwestern Argentina ( Fig. 2 ). The population is small and camouflaged due to the color of the leaves similar to the substrate and the disposition of the plants at ground level. The Espinazo del Diablo is not located within any protected area and is a site of interest for trekking of medium difficulty, but it is a point with low tourist impact. Taking into account the two known occurrence points documented for the new species, following the IUCN Red List categories, criteria, and guidelines ( IUCN 2012, 2022), and with the failure of calculate the polygon of extent of occurrence (EOO), we inform an area of occupancy (AOO) of 4 km 2. Following the B2ab(ii) criteria of the IUCN Red List of threatened species, taking into account the reduced area of occupancy of less than 10 km 2 until new localities are found, and conceiving the Espinazo del Diablo as one locality or a single distinctive geographic and ecological area in which a single threatening event (i.e. trekking activities) can rapidly affect all individuals of the present species, V. watsoniana is provisionally categorized as Critically Endangered (CR).

Figures

FIGURE 1. Viola watsoniana. A. Habit. B. Leaf, upper surface view. C. Leaf, lower surface view. D. Flower, semi-lateral view including peduncle and bracteoles. E. Flower, frontal view. F. Lower petal, ventral surface. G. Lateral petal, ventral surface. H. Upper petal, ventral surface. I. Upper stamen, ventral surface. J. Lower stamen, ventral surface, showing the basal appendage. K. Gynoecium showing style crest, frontal view. L. Style apex showing style crest and stigma in lateral view. M. Seed. From F. O. Zuloaga et al. 14262 (SI, holotype) and F.O. Zuloaga et al. 13575 (SI).

FIGURE 2. Distribution map showing the known occurrence site of Viola watsoniana (red star) and the allied species from sect.Rosulatae of northwestArgentina with which it is compared, V. rodriguezii (light blue rhombus), V.roigii (pink square), and V. xanthopotamica (green circle).Argentinian provinces are indicated with acronyms (C: Catamarca. J: Jujuy. LR: La Rioja. Sa: Salta. SJ: San Juan. T: Tucumán).At the upper right, a map of South America showing the distribution area of the species indicated with a black rectangle.

FIGURE 3. Photos of vegetative and reproductive structures of Viola watsoniana under a stereoscopic microscope. A. Habit. B. Leaf, lower surface view. C. Leaf, upper surface view. D. Seed. E. Flower (US: upper sepal, LaS: lateral sepals, LS: lower sepals, UP: upper petals, LaP: lateral petals, LP: lower petal, UA: upper anthers, LA: lower anthers, FG: gynoecium in frontal view, LaG: gynoecium in lateral view). From F. O. Zuloaga et al. 14262 (A−D) and F.O. Zuloaga et al. 13575 (E). Scale: 1 mm.