Stellaria spinulosa Montesinos & Borsch, 2023

Montesinos-Tubée, Daniel B. & Borsch, Thomas, 2023, Molecular phylogenetics and morphology reveal the Plettkea lineage including several members of Arenaria and Pycnophyllopsis to be a clade of 21 South American species nested within Stellaria (Caryophyllaceae, Alsineae), Willdenowia 53 (3), pp. 115-148 : 136

15. Stellaria spinulosa Montesinos & Borsch , nom. nov.

≡ Arenaria aphanantha Wedd. in Ann. Sci. Nat., Bot., ser. 5, 1: 293. 1864 [non Stellaria aphanantha Griseb. in Abh. Königl. Ges. Wiss. Göttingen 24: 27. 1879]. –

Lectotype (designated here): Peru, 1839–1840, C. Gay 1818 ([ P ( P00335797 )]; isolectotype: ([ MO-840929 ]) .

Morphological description — Perennial herb, varying from few stems up to 50 cm long to forming dense mats 2–4 cm high; root woody. Stems decumbent, creeping and with branches distinctly shorter than stems, bearing remains of old foliage along stems; internodes 1–1.5 mm long; sparsely pubescent with erect 0.1–0.3 mm long trichomes. Leaves alternate, lamina lanceolate to linear-lanceolate, 4–6 mm long and 1–1.5 mm wide, coriaceous, with acuminate to subaristate apex, densely ciliate near truncate base. Plants bisexual-hermaphrodite. Flowers perigynous, terminal, on hirsute, thick, 3.5–4 mm long peduncles, but these hidden by uppermost leaves; calyx cylindrical to rarely subcampanulate, 3.5–4 mm long and 1.5–2 mm wide, crateriform, usually thickened at bottom; sepals 5, lanceolate, cupuliform at base, involute, 3–3.5 mm long and c. 0.8 mm wide, apex acute, light green to pale yellowish, glabrous on surface and along margins; petals 5, strongly reduced, translucent, ovate, apex obtuse, 1.2–1.6 mm long and 0.7–0.8 mm wide; stamens 4 or 5, episepalous, 1.1–1.3 mm long; ovary cylindrical-turbinate, 0.5–0.7 mm long and 0.6–0.8 mm wide, style 3-fid, stigma aciculate. Capsule ovoid, c. 1 mm long, containing 2 or 3 seeds, orbicular, 0.5–0.6 mm in diam., testa maroon, shiny and distinctly tuberculate, cells bearing whitish asymmetrical protuberances.

Distribution — Stellaria spinulosa occurs in a variety of highland ecosystems across Peru and is considered as the most collected species of the clade (as observed in the material from the different herbaria visited) and extends to Ecuador. Jørgensen & León-Yánez (1999) mentioned the occurrence of the species in Ecuador, which can be confirmed based on an analysis of material stored at MO according to Tropicos.org (2023) and as evaluated by the first author during two visits to MO in 2013 and 2016 and more recently, at PRC, four collections were identified to be S. spinulosa located mostly in central Ecuador, between Chimborazo and Cuicocha. The altitudinal range is from 2800–5000 m according to the specimens evaluated.

Etymology — The epithet refers to the spine-like leaves of the plant, which can be felt as tingling by simple touch; spinulosa is derived from the Latin spinula (small spine) in relation to the thorny and pungent characters of the leaves. The former epithet aphanantha is derived from the Greek aphanes (invisible obscure) and anthos (flower), probably referring to the resemblance of the flower sepals to the leaves.

Notes — The specimen C. Gay 1818 ( P00335797 ) is selected as the lectotype for being most representative with a complete set of morphological characters. As evidenced by this specimen, the species is easily distinguishable from the other members of the clade by the intense yellowish colour of the stems and leaves, the stiff ovate leaf lamina and the nearly sessile flowers with long calyx, the presence of staminoid petals reduced to filaments and the tubercle seeds, which is characteristic for this kind of habit.