Stellaria apurimacensis Montesinos & D. Cornejo, 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 : 130

3. Stellaria apurimacensis Montesinos & D. Cornejo , sp. nov. – Fig. 5A, B , 6 ; Supplementary appendix S11.

Holotype: Peru, Apurimac, Cotabambas, Haquira , NW of Haquira , 4525 m, 28 Mar 2017, D. Montesinos & D. Cornejo 5194 ( HSP [HSP-9443!]; isotypes: B [ B 10 0761536 !], CUZ!, F!, USM!).

Diagnosis — The new species is distinguishable by its rosette or small mat, ovate leaves, apetalous flowers and short internodes.

Morphological description — Annual herb, densely ramified at base, forming cushions c. 2 cm high and 6–10 cm in diam.; roots fibrous. Stems decumbent or creeping, 4–6 cm long, often densely branched and covered by older leaves in central and lower parts; internodes 4–10 mm long, glabrous. Leaves opposite, petiolate, lamina elliptical-lanceolate, 2–3 mm long and 0.8–1.2 mm wide, sparsely pilose along margin, trichomes 0.1– 0.3 mm long, acuminate, plain or curved, thin, slightly involute, glabrous on both sides, midrib protuberant on underside. Plants bisexual-hermaphrodite. Flowers on rigid or slightly curved 2–5 mm long glabrous peduncles, terminal; perigynous, 2.5–3.5 mm long and 1.5–2.2 mm wide, calyx campanulate, glabrous; sepals 5, imbricate, slightly involute, lanceolate-ovate, cupuliform at base, apex acuminate, glabrous, 2–3 mm long and 1–1.5 mm wide, pale green to yellowish; petals 5, translucent, ovate, 0.8–1.2 mm long and 0.4–0.6 mm wide, apex rounded; stamens usually 10, episepalous, filaments 0.3–0.4 mm long; ovary ovoid, 0.4–0.6 mm long and 0.3–0.5 wide; style 3-fid, curved, glandular, 0.3–0.5 mm long. Capsule ovoid, glabrous, c. 2.2 mm long, containing 4–6 seeds, these roundish to ovate, 0.4–0.5 mm long and 0.3–0.4 mm wide; testa pale brown, cells with tuberculate and stellate protuberances of c. 50 µm in diam.

Distribution and ecology — This species occurs in the Apurimac department on the boundary with the Cusco department at altitudes of 3980–4530 m in open grasslands with rocky outcrops in which species such as Stipa ichu Ruiz & Pav. ( Poaceae ), Senecio adenophyllus Meyen & Walp. and S. algens Wedd. ( Asteraceae ) occur.

Etymology — The epithet name is allusive to the Apurimac department located in S Peru, the site of the type locality.

Vernacular name — Hatun Yuraq Tika, given in Quechua language (Zoilita Salazar Patiño, Arequipa, pers. comm.).

Notes — Stellaria apurimacensis is morphologically similar to S. galianoi but differs by the internode length (4–10 mm vs. 2–15 mm in S. galianoi ), smaller leaves (2–3 mm long and 0.8–1.2 mm wide vs. 3–5 mm long and 1.4–1.8 mm wide in S. galianoi ), shorter peduncles (2–5 mm vs. 7–15 mm in S. galianoi ), wider sepals (1–1.5 mm vs. 0.8–1 mm in S. galianoi ) and smaller seeds (0.4–0.5 mm long vs. 0.6–0.8 mm long in S. galianoi ). Stellaria apurimacensis differs from S. macbridei by the longer internodes (4–10 mm vs. 3–4 mm in S. macbridei ), smaller leaves (2–3 mm long and 0.8–1.2 mm wide vs. 5–7 mm long and 2–2.5 mm wide in S. macbridei ) and from S. utcubambensis by the weaker stems and leaves (vs. robust in S. utcubambensis ).

Figures

Fig. 5. SEM images of seeds of Stellaria species described as new species – A, B: S. apurimacensis; C, D: S. galianoi; E, F: S. utcubambensis; G, H: S. xanthophylla. – Scale bars:A, C, E, G = 0.5 mm; B, D, F, H = 50 μm.

Fig. 6. Morphological details of Stellaria apurimacensis – A: ramified stem; B: leaves; C: detail of pilose hairs on leaf margins; D: mature flower with capsule; E: sepals; F: tuberculate seeds. – From Montesinos & Cornejo 5194b. – Scale bars: A = 2 mm; B, D, E = 0.5 mm; C = 100 μm; F = 200 μm.