Sedum dormiens Cuevas, Perez-Calix & P. Carrillo 2022, sp. nov.
Creators: name: Cuevas-Guzmán, Ramón
name: Pérez-Calix, Emmanuel
name: Carrillo-Reyes, Pablo
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Saxifragales
Crassulaceae
Sedum
Sedum dormiens

description: Sedum dormiens Cuevas, Pérez-Calix & P. Carrillo, sp. nov. (Fig. 1, 2)
Type: — MEXICO. Jalisco state: Municipio de Cuautitlán de García Barragán, Cerro Las Capillas, in rocky areas within the Pinus durangensis forest, 2800 m a.s.l., 1 st Nov 2009 (fl, fr), Cuevas, Cuevas & Medina 9882 (holotype: ZEA! Isotypes IEB, IBUG).
Diagnosis:— Sedum dormiens resemble most to Sedum quadripetalum with which it shares tetramerous flowers, but in the latter the roots are tuberous, the leaves are bigger (15–20 × 5–7.5 mm) and the nectaries are greenish-yellow, whereas in S. dormiens the roots are capillary, the leaves smaller (6–7 × 1.8–2.5 mm) and the nectaries are red. In S. quadripetalum, the winter leaves form basal rosettes and the species is biennial, while in S. dormiens, dormant aerial buds are formed and the species is chamaephytic.
Chamaephytic herb, rupicolous, 4–10 cm tall, sometimes prostrate with branches of up to 15 cm in length. It forms dense colonies from a few to hundreds of m 2 in area. Plants turn reddish during flowering and fruiting. Stems with long, almost leafless, stolons ending in compact sterile shoots forming winter-dormant buds protected by scarious scales, stems from the previous season reddish-brown and hollow, while those of the current season are solid, with a spongy pith, both covered with a strong, transparent epidermis. Lower leaves are alternate, upper leaves are oppositecrossed or sub-opposed, linear-elliptic to slightly spatulate, glabrous, reticulate and sometimes papillose, 6–7 × 1.8–2.5 × 1 mm, with spur of 0.5–1 mm in length, concave ventrally and convex dorsally. Inflorescences are cymes of 2–3 cincinni, each cincinnus with 1–4 flowers. Stems are papillose. Pedicels of 1 mm in length, white-pink. Flowers are 4 (5)–merous, 9–10 mm in diameter; sepals of equal size in each flower, fleshy, glabrous, elliptic to elliptic-oblong, 2.7– 4 × 1.2–1.5 × 0.6–0.7 mm, base spurred; petals cruciform, linear to elliptic-lanceolate, 4–5 × 1.5 mm, acute, with the midrib dorsally keeled and very strong, white with pink to reddish bases; stamens 8, 4 epipetalous and 4 alternipetalous, 3.5–4 mm long, pinkish to reddish basally, anthers reddish, 0.5 × 0.3 mm, epipetalous stamens open later; nectaries are oblong, red, 0.6–0.8 × 0.2 mm, rounded at the apices; carpels are 4 mm in length, divergent, connated ventrally ½–¾ in length, beaks of 0.5–0.7 mm in length; 2–6 ovules per carpel, cylindrical, 0.6–0.8 × 0.2–0.25 mm. The fruit is ventrally dehiscent, 4–4.5 mm in length, each carpel with 2–4 seeds. Seeds are cylindrical or claviform, 0.7–1 mm in length, reticulate-papillate, reddish-brown.
Habitat, distribution, and phenology: — Sedum dormiens is a rupicolous species which appears to be dead in the cold, dry season of the year (December to early June), but in June, when the atmospheric humidity increases, even without precipitation, a reaction occurs in S. dormiens; the buds lose their dormancy and generate aerial adventitious roots with new individuals that anchor themselves to the ground and form broad Sedum colonies (field observation). This event seems to be concomitant with the response of mosses to increased atmospheric humidity and with which S. dormiens coexists. Sedum dormiens is only known from three localities in western Mexico, located between 2400 to 2860 m a.s.l. in elevation, in the highest parts of the Sierra de Manantlán. It grows in volcanic rock and open areas in Pinus durangensis Martínez (1942: 23) forest, coexisting with Arbutus occidentalis McVaugh & Rosatti (1978: 303–304), Agave manantlanicola Cuevas & Santana-Mich. (2012: 330), Agrostis novogaliciana McVaugh (1983: 41–42), Arbutus xalapensis Kunth (1819: 279–280), Castilleja albobarbata Iltis & G.L. Nesom (2003: 1343–1346), Castilleja macvaughii Holmgren (1976: 203–204), Comarostaphylis discolor (Hook.) Diggs subsp. manantlanensis Diggs (1988: 205), Disocactus speciosus (Cav.) Barthlott, (1991: 87), Lopezia miniata Lag. ex DC. (De Candolle 1813: 121), Microspermum debile Bentham (1840: 64), Muhlenbergia dumosa Scribner ex Vasey (1892: 71), Pedicularis glabra McVaugh & Mellich. (1975: 58–60), Quercus laurina Bonpl. (von Humboldt & Bonpland 1809: 32), Sedum jaliscanum S. Watson (1890: 148), Sisyrinchium schaffneri S. Watson (1883: 160), Tagetes filifolia Lagasca (1816) and Weldenia candida Schult. f. (1829: 3), among other species.
Flowering of S. dormiens occurs from September to November, while fruiting has been observed in October and November.
Etymology:—The name of the species alludes to the presence of dormant aerial buds protected by strong scarious scales, which maintain perennity during the dry and cold season of the year.
Conservation Status:—According to the categories and criteria of the IUCN Red List (IUCN 2012), Sedum dormiens is assigned a preliminary status of “Endangered” EN (B2a). Its known and estimated geographical distribution is less than 500 km 2 in area, and it has been recorded from only three localities.
Additional specimens examined (paratypes):— MEXICO. Jalisco: Municipio de Cuautitlán de García Barragán: Cerro Las Capillas, 2800 m a.s.l., 7 th Jan 1980 (st), Iltis, Schatz, Sorensen & Matekaitis 2414 (WIS, MEXU); Top of sharp crest of the Sierra de Manantlán, Oriental just E of “ Cerro Las Capillas ”, along from road to “ Cerro La Cumbre ” to “ Los Jardines ”, 19 km due SSE of El Chante, 19°33’15’’N; 104°09’W, 2800-2860 m a.s.l., 10 th Oct 1980 (fl), Iltis & Guzmán 3216 (WIS); 35 km to the southeast of Autlán, between San Miguel and El Rincón de Manantlán, 2400 m a.s.l., 4 th Sep 1981 (fl), Vázquez-García & Nieves-Hernández 471 (IBUG); Cerro Capulín, 19°33’N; 104°09’W, 2750 m a.s.l., 9 th Mar 1987 (st), Iltis, Benz, Vázquez & Cházaro 29392 (WIS); los Picachos del Pozanco, 19°32’54.3” N; 104°07’49.6” W, 2830 m a.s.l., 1 st Nov 2009 (fl, fr), Cuevas, Cuevas & Balcázar 9910 (ZEA); 1 st Nov 2009 (fl, fr), Cuevas, Cuevas & Balcázar 9917 (ZEA); Cerro Las Capillas, 0589169 and 2162369 Datum WGS84, 2846 m a.s.l., 9 th Oct 2012 (fl, fr), Cuevas, Carrillo-Reyes & Pérez-Calix 10936 (ZEA, IEB, IBUG).
description: Published as part of Cuevas-Guzmán, Ramón, Pérez-Calix, Emmanuel & Carrillo-Reyes, Pablo, 2022, Sedum dormiens (Crassulaceae, Sempervivoideae, Sedeae): a new species from the Sierra de Manantlán, Mexico, pp. 77-85 in Phytotaxa 530 (1) on pages 80-83, DOI: 10.11646/phytotaxa.530.1.6, http://zenodo.org/record/5823965