Stellaria macbridei 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 : 134-135

10. Stellaria macbridei Montesinos & Borsch , nom. nov.

≡ Arenaria crassipes Baehni & J. F. Macbr. in Publ. Field Mus. Nat. Hist., Bot. Ser. 13(2): 598. 1937 [non Stellaria crassipes Hultén in Bot. Not. 1943: 261. 1943].

– Holotype: Peru, Lima, Río Blanco, 3000 m, prostrate on upland slopes , Macbride 812 ( F [ F0042702F image!]; isotypes: NY [ NY00342439 image!], US [ US00103284 image!]) . – Fig. 1D .

Morphological description — Perennial herb, individual stems visible (not caespitose); root thick, reaching c. 4 cm deep. Stems 7–12 per individual, decumbent to ascending, 3–5 cm long; internodes 3–4 mm long, densely hirsute near nodes; trichomes irregularly shaped, multicellular, uniseriate, 0.5–1 mm long. Leaves, with broad and hirsute petioles, alternate; lamina oblong, 5–7 mm long and 2–2.5 mm wide, subcoriaceous or membranous, thickened at base, shiny, glabrous on both sides, thin, margins ciliate or hairy-ciliate, apex acuminate and slightly involute, only midrib hirsute. Plants bisexual-hermaphrodite. Flowers perigynous, on 1–1.8 mm long ciliate peduncles, axial and terminal; cylindrical-oblong, 2.5–3 mm long and 1.2–1.8 mm wide; calyx cylindrical-turbinate, thicker at base, crateriform; sepals 5, imbricate, narrowly lanceolate, 2–2.3 mm long and 0.4–0.6 mm wide, glabrous on surface, light green to bright yellow, apex acute-attenuate, involute, folded and forming a narrow cylinder that covers capsule; petals 5, reduced, translucent-stramineous, ovate, apex obtuse, 1–1.3 mm long and 0.2–0.4 mm wide; stamens 4 or 5, episepalous, 1–1.5 mm long; ovary ovoid-turbinate, 0.4–0.8 mm long and 0.6–0.8 mm wide, style 3-fid, stigma aciculate. Capsule ovoid, 0.9–1.2 mm long containing 4 seeds, these orbicular, 0.2–0.3 mm in diam., testa reddish-maroon and shiny, cells bearing light maroon tubercles.

Distribution and ecology — Stellaria macbridei is endemic to central Peru (Cano & Sánchez Vega 2006) occurring in puna grasslands ecosystems that receive continuous rainfall throughout the year, it is distributed in Áncash, Huánuco, Junín and Lima departments at altitudes of 4200–4800 m.

Etymology — The specific epithet refers to J. F. Macbride (1892–1976), American botanist who provided the last comprehensive revision for Stellaria and Arenaria from Peru and also was one of the authors who originally described this species.

Notes — Macbride (1936) mentioned that Stellaria macbridei has similarities with S. congesta but differs from that species by the tuber-like root and the small erect habit. Other differences include suboblong leaf form (ovate in S. congesta ) and the narrowly lanceolate sepals (lanceolate in S. congesta ). The two sequenced specimens are sisters and form a distinct lineage within the Plettkea clade in both the plastid and nuclear trees ( Fig. 3 , 4 ) underscoring the identity of S. macbridei as a distinct and eventually monophyletic species.

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. 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.