Stellaria galianoi 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 : 132

7. Stellaria galianoi Montesinos & Borsch , sp. nov. – Fig. 1C , 5C, D , 7 ; Supplementary appendix S12.

Holotype: Peru, Cusco, Urubamba, Urubamba, Puerto Yanamayo , Patacancha , road to Ocobamba , 4440 m, 3 Apr 2016, D. Montesinos 4572 ( HSP [ HSP-9443 !]; isotypes: B [ B 10 0766217! ], O [ O-227237! ], USM!).

Diagnosis — This species is easily distinguished by its long internodes (2–15 mm long), leaf laminas bearing white protuberances, absent characters in other species of Stellaria sect. Plettkea .

Morphological description — Perennial herb, forming diffuse mats, 4–8 cm high and 20–60 cm in diam.; roots fibrous. Stems decumbent or creeping 8–25 cm long, densely ramified at base and along whole length, glabrous, or nearly so (scarcely covered with minute papillae), covered by older leaves in central and lower parts; internodes 2–15 mm long. Leaves opposite, sessile; lamina oblanceolate-oblong to gladiate, plain or curved, nearly involute, glabrous on both sides, 3–5 mm long and 1.4–1.8 mm wide, midrib protuberant on underside, margin from base to mid of lamina with 4–7 multicellular pilose hairs (0.3–1 mm long, 6–14 cells) born on protuberances, usually persistent on older leaves; base truncated and apex aristulate; leaves pale green to yellow-brownish with age. Plants bisexual-hermaphrodite. Flowers perigynous, on rigid 7–15 mm long and glabrous peduncles, terminal, 2.2–3 mm long and 3–5 mm wide; calyx campanulate, glabrous; sepals 5, lanceolate, slightly involute, cupuliform at base, apex apiculate-aristulate, glabrous, 1.8–2.4 mm long and 0.8–1 mm wide, pale green to yellowish; petals 5, white, subglandular, ovate, with revolute obtuse apex, 2–3 mm long and 1–1.5 mm wide; stamens usually 10, episepalous, filaments often curved toward centre of flower, 0.3–0.5 mm long; anthers roundish to elliptical, reniform, yellowish and 0.15–0.3 mm long; style 3-fid, curved, glandular, pistil 0.5–0.7 mm long; stigma papillate or glandular; ovary cylindrical-ovoid, 0.7–1.1 mm long and 0.8–1.1 mm wide. Capsule ovoid, glabrous, c. 1.8 mm long and 2.5 mm wide, containing 10–12 seeds, these ovate or roundish, 0.6–0.8 mm long and 0.4–0.6 mm wide; testa brown, grooved, cells with bulgy stellate protuberances.

Distribution and ecology — Peru, Cusco, Urubamba. The species inhabits continuously moist environments dominated by tussock grasslands and bryophyte communities located on high passes that divide the inter Andean valleys, between the highland tropical forests and the puna scrublands in the upper basins near the Urubamba River lower slopes. The altitudinal range is 4230–4400 m and is restricted to this region. The exhaustive field collection of Caryophyllaceae in most parts of Peru for the past seven years and examination of nearly all available herbarium material did not reveal additional areas where the plant occurs. Nevertheless, further fieldwork in Urubamba is needed better understand the frequency and population structure of the species. Flowering specimens have been collected from March to May; fruiting specimens have been observed between April and June (pers. obs.). Associated taxa are: Gentianella sp. ( Gentianaceae ), Plantago rigida Kunth ( Plantaginaceae ), Senecio rhizomatus Rusby ( Asteraceae ) and Stellaria weddellii Pedersen ( Caryophyllaceae ), among others.

Etymology — The specific epithet refers to Prof. Washington Galiano (1950–), for his devoted career on studying the floristic diversity of the Cusco department in S Peru.

Notes — Stellaria galianoi is most likely monophyletic and is phylogenetically rather isolated among other members of the Plettkea clade ( Fig. 3 , 4 ). This species has the longest internodes of vegetative stems across the Plettkea clade, eventually, in the uppermost the internode is long, sometimes as reaching 1.5 cm. This character makes it easy to recognize among the apetalous taxa of Andean Stellaria . The new species differs from the known South American species of Arenaria by its leaf form and by the densely tuberculate seeds. Furthermore, S. galianoi differs from S. apurimacensis by the internode length (2–15 mm vs. 4–10 mm in S. apurimacensis ), larger leaves (3–5 mm long and 1.4–1.8 mm wide vs. 2–3 mm long and 0.8–1.2 mm wide in S. apurimacensis ), longer peduncles (7–15 mm vs. 2–5 mm in S. apurimacensis ), narrower sepals (0.8–1 mm vs. 1–1.5 mm in S. apurimacensis ) and larger seeds (0.6–0.8 mm long vs. 0.4–0.5 mm long in S. apurimacensis ). Stellaria galianoi differs from S. andina in the leaf form (oblanceolate-oblong to gladiate vs. ovate in S. andina ) and longer peduncles (7–15 mm vs. 1–4 mm in S. andina ).

Figures

Fig. 1 (p. 120). Habit in natural environment of some species of the Plettkea clade of Stellaria. – A: S. alpamarcae, Huánuco, Huamalies, 4400 m (Montesinos 5487, CAR440); B: S. congesta, Huánuco, Huamalies, 4200 m (Montesinos 4900, CAR661); C: S. galianoi, Cusco, Urubamba, near Malaga pass, 4240 m, shady rocky slopes in moist grasslands (Montesinos & von Mering 4523, CAR677); D: S. macbridei, Huánuco, Lauricocha, 4790 m (Montesinos 4590, CAR630); E: S. pedunculosa, Moquegua, near Ticsani volcano, 4818 m, pumice slopes (Montesinos & Chicalla 5395d, CAR777); F: S. utcubambensis, Amazonas, Chachapoyas, Leymebamba, Tajopampa, 3700 m, rocky summits of recently burnt slopes (Montesinos & Garcia 4979, CAR433); G: S. weberbaueri, Arequipa, 4876 m, forming cushions with eventually elongated stems (Montesinos & von Mering 4496, CAR670); H: S. xanthophylla Amazonas, S Leymebamba, 3540 m, forming dense mats (Montesinos 6970a, CAR691). – All photographs by Daniel B. Montesinos-Tubée.

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. 7. Morphological details of Stellaria galianoi – A: ramified stem; B: detail of pilosity on leaf surface; C: detail of leaves; D: mature flower with capsule; E: tuberculate seeds. – From Montesinos 4572. – Scale bars: A = 5 mm; B–E = 1 mm.

Fig. 3. Bayesian majority rule consensus tree inferred from combined trnK-matK-psbA + trnL-F sequence matrix including indels. Posterior probabilities are above branches, parsimony jackknife values are below branches left and in italics, and maximum likelihood bootstrap percentages right and in bold. The monophyletic Stellaria sect. Plettkea is deeply nested within the genus Stellaria. Species previously classified within Arenaria and Pycnophyllopsis are annotated with a red or green bar, respectively.

Fig. 4. Bayesian majority rule consensus tree inferred from nuclear ribosomal (ITS) sequence matrix including indels. DNA posterior probabilities are above branches, parsimony jackknife values are below branches left and in italics, and maximum likelihood bootstrap percentages right and in bold. The monophyletic Stellaria sect. Plettkea is deeply nested within the genus Stellaria. Species previously classified within Arenaria and Pycnophyllopsis are annotated with a red or green bar, respectively.