Echeveria sotoi Rosales & Quirarte, 2024

Echeveria sotoi Rosales & Quirarte View in CoL sp. nov. Figs. 2–4 View FIGURE 2 View FIGURE 3 View FIGURE 4 .

Type: — MEXICO. Michoacán: municipio de Aquila, macizo rocoso ca. 5 km al NE de Pichilinguillo, sobre el camino a Santiaguillo , 470 m, 14 January 2023, J. Quirarte & G. Soto 1 (holotype: IBUG!; isotype: MEXU!) .

Diagnosis: — Echeveria sotoi is similar to E. gibbiflora ( Fig. 5 View FIGURE 5 ) in the tall inflorescences with numerous cincinni and pinkish flowers; however, the former differs by having a stem thickness of 2.0– 2.5 cm (2.5–5.0 cm), a leaf width of 3.0–8.0 cm (vs. 8.0–18.0 cm),

oblanceolate to oblanceolate-obovate leaves (vs. broadly obovate-orbicular), light green to purplish-green or orangish-pink leaves (vs. glaucous-green with tendency to show reddish colouration in the whole leaf), a peduncle thickness of 0.9–1.1 cm (vs. 1.5–2.0 cm), horizontally spreading to obliquely ascending cincinni (vs. pendulous), a nectary scale width of 0.2 cm (vs. 0.3 cm), and a preference for limestone soils (vs. volcanic soils). Also, E. sotoi resembles E. longiflora in the evident stem, peduncle thickness, and pinkish flowers; nevertheless, it differs from the latter by having oblanceolate to oblanceolate-obovate leaves (vs. obovate-orbicular), light green to purplish-green or orangish-pink leaves (vs. vetiver-green, more or less glaucous, tinged light vinaceous-drab), (3–) 8– 14 cincinni per inflorescence (vs. 2–3), horizontally spreading to obliquely ascending cincinni (vs. pendulous), usually horizontally spreading to obliquely ascending sepals (vs. widely spreading to slightly recurved), a corolla length of 1.2–1.9 cm (vs. 1.9–2.2 cm), a corolla with yellow or orange colourations (lacking any trace of yellow or orange colouration), a nectary scale width of 0.2 cm (vs. 0.3 cm), and whitish nectary scales (vs. straw-yellow).

Description: —Plants perennial, glabrous, succulent, caulescent, solitary or sometimes offsetting, rupicolous, up to 170.0 cm tall with inflorescence. Roots fibrous, somewhat thickened with age. Stems simple to very rarely branched, 15.0–65.0 cm long, 2.0– 2.5 cm in diameter, erect to sometimes curved or inclined, grayish-brown, olive-green to reddish distally, bumpy, with scars of the fallen leaves 0.9–1.1 cm wide, sometimes with old peduncle segments attached. Rosettes terminal, 15.0–40.0 cm in diameter, lax. Leaves spirally arranged, 12–20 per rosette, 8.0–25.0 cm long, 3.0–8.0 cm at the widest point, oblanceolate to oblanceolate-obovate, pseudo-petiolate, rounded at the apex, provided with a small mucro, more or less horizontally spreading to ascending, light green to purplish-green or orangish-pink, smooth, the abaxial surface keeled, the adaxial surface canaliculate to the base. Margins entire to undulate or crenulate, reddish, sometimes slightly hyaline. Inflorescences lateral panicles, 1–2 per rosette, mostly 60.0–140.0 cm long. Peduncles 0.9–1.1 cm thick at the base, erect, pale yellowish-green to pinkish. Bracts 3.0–15.0 cm, oblanceolate, green to purplish. Cincinni (3–) 8–14 per inflorescence, 5.0–20.0 cm long, straight to somewhat curved, horizontally spreading to obliquely ascending, pink to greyish-purple. Flowers 4–17 per cincinnus. Pedicels 0.4–0.9 cm long, 0.2–0.3 cm in diameter, thickened at the apex, nearly straight to slightly curved. Calyx 1.7–2.1 cm in diameter, discoid. Sepals very unequal, 0.5–1.0 cm long, 0.2–0.4 cm at the widest point, triangular-lanceolate, rounded at the apex, usually obliquely ascending, reddish-green to pinkish, sometimes pruinose, the abaxial surface concave, the adaxial surface flattish to concave. Corolla 1.2–1.9 cm long, 0.7–1.2 cm wide, tubular, onion-shaped to conoid in bud, cylindrical-pentagonal at anthesis. Petals 0.5–0.6 cm at the widest point, fused at the base, lanceolate, dorsally keeled, salmon-pink to reddish-pink on the outer surface, with yellow or orange colourations, orangish-white to pinkish on the inner surface. Nectary scales 0.2 cm wide, reniform, whitish. Stamens 10, 5 episepalous, 5 epipetalous. Filaments 0.7–0.9 cm long in episepalous stamens, 0.4–0.6 cm long in epipetalous stamens, erect, whitish to yellowish. Anthers 0.2 cm long, pale yellow or beige. Gynoecium 1.1–1.4 cm long, 0.5–0.6 cm at the widest point near the base, pyriform. Carpels 5, free. Ovaries whitish-green to pale yellowish. Styles dark red to purplish-red, sometimes greenish proximally. Stigmas translucent yellow. Fruits follicles, brownish. Seeds inconspicuous, reddish-brown.

Distribution and ecology: —Current records of Echeveria sotoi indicate that this is a narrow endemic species, confined to a mountain near the town of Huahua (municipality of Aquila, coastal Michoacán), within the Pacific Lowlands biogeographic province ( Morrone et al. 2017). Here, the species grows on two limestone outcrops at elevations between 350– 500 m. The dominant vegetation is thorn forest, including the following species: Adenophyllum aurantium ( Linnaeus 1753: 877) Strother (1986: 376) , Agave kristenii A.Vázquez & Cházaro in Vázquez-García et al. (2013: 326), Bursera denticulata McVaugh & Rzedowski (1965: 365) , Cephalocereus nudus Dawson (1948: 12) , Cyrtopodium macrobulbon ( Lexarza 1825: 42) Romero-González & Carnevali (1999: 331) , Hechtia michoacana Burt-Utley et al. (2011: 5) , Mammillaria beiselii Diers (1979: 60) , species of Tillandsia Linnaeus (1753: 286) , and others. In this specialized habitat, E. sotoi uses the rock crevices or roots of associated species for germination and benefits from its proximity to the Pacific Ocean (4–6 km as the crow flies), which provides optimal moisture conditions for the growth of plantlets.

Phenology: —The plants start developing their inflorescences in summer, usually around July. They are in full bloom during late fall and early winter, from late November to mid-January. Fruits and seeds complete their ripening process between mid-January and mid-March.

Eponymy: —The authors are honoured to name this species after Mr. Gerardo Soto Mendoza (Aquila, Michoacán) ( Fig. 4 View FIGURE 4 ), a passionate nature lover who discovered this species back in 2013. He was kind enough to provide us with plants for study and cultivation and guide one of us (Jaime Quirarte) to their natural habitat. Moreover, he has contributed to the knowledge and protection of biodiversity in the Sierra-Costa region of Michoacán, documenting the natural history of various animals (especially jaguars and other felines) and collecting seeds for the Comisión Nacional Forestal (CONAFOR).

Conservation status: — Echeveria sotoi grows on rocky outcrops along a dirt road, which makes it susceptible to over-collection. Additionally, climate change and natural disasters such as landslides could have a severe impact on the ecological niche of the species. As calculated using GeoCAT ( Bachman et al. 2011), E. sotoi has an Extent of Occurrence (EOO) of 0.0 km 2 and an Area of Occupancy (AOO) of 8.0 km 2 (using 2 km cell width). Based on this information, the species should be categorized as Critically Endangered following the criteria B1ab (i,ii,v) + B2ab(i,ii,v) of the IUCN (2022).

Additional specimens examined: — MEXICO. Michoacán: municipio de Aquila, Risco Chino, 5 km al N de Huahua, sobre afloramientos de caliza, 380 m, 27 January 2023, S. Rosales 9 (IBUG!); municipio de Aquila, 10 km al S de La Parota, sobre la brecha de Playa El Zapote a Santiaguillo, 450 m, 28 January 2023, S. Rosales 10 (MEXU!).