Stellaria tetrasticha (Mattf.) M. T. Sharples & E. A. Tripp.

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 : 137

17. Stellaria tetrasticha (Mattf.) M. T. Sharples & E. A. Tripp. in Syst. Bot. 44: 871. 2019

≡ Plettkea tetrasticha Mattf. in Schriften Vereins Naturk. Unterweser, n.s., 7: reprint p. 21 (25). 1934 ≡ Pycnophyllum mattfeldii J. F. Macbr. in Publ. Field Mus. Nat. Hist., Bot. Ser. 13(2): 611. 1937 [non Pycnophyllum tetrastichum J. Rémy in Ann. Sci. Nat., Bot., ser. 3, 6: 356. 1846] ≡ Pycnophyllopsis tetrasticha (Mattf.) Timaná in Lundellia 20: 8. 2017.

– Holotype: Peru, Áncash, Cajatambo, Schwarze Cordillere über Ocros , auf dürftig bewachsenem, steinigem Boden , 4500–4800 m, A. Weberbauer 2804a (B†). – Neotype (designated by Timaná 2017: 8): Peru, Áncash, Yungay Province, Huascarán National Park , Llanganuco sector, Quebrada Demanda , W of Chacraraju base camp , 09°01'S, 77°36'W, 4750–4900 m, 13 Apr 1985, D. N. Smith & V. Cautivo 10287 ( MO- 052068 !; isoneotype: F!) .

Morphological description — See Timaná (2005).

Distribution — Central Peru, Áncash department inside the Huascarán National Park on highland peaks at altitudes of 4500–4900 m, where considered a narrow endemism.

Notes — Stellaria tetrasticha was originally described as a member of the genus Plettkea by Mattfeld (1934) and later accepted by Bittrich (1993). The species has a mat form with spreading stems, ovate leaves c. 2 mm long bearing carinate acute apex and sepals with ovate-oblong form. Later, Timaná (2017) named Pycnophyllopsis tetrasticha (Mattf.) Timaná based on the morphological affinities found within flower measurements in the neotype he selected. Sharples & Tripp (2019) included a sample of the species in their phylogenetic analysis showing it to be strongly supported as a member of the Plettkea clade.