Erigeron morelensis Greenman (1905: 256–257)

Cerros-Tlatilpa, Rosa, Miguel-Vázquez, Mónica I., Caspeta-Mandujano, Juan M., Méndez-Cano, Rafael & Guerrero, Jose A., 2023, Erigeron morelensis (Asteraceae): a rediscovery after more than 120 years of a microendemic and threatened species in central Mexico, Phytotaxa 587 (3), pp. 211-217 : 212-215

Erigeron morelensis Greenman (1905: 256–257) ( Figs. 1 , 2 )

Type:— MEXICO. Morelos: wet cliffs, mountain cañon near Cuernavaca , 6500 ft, 15 May 1898, C.G. Pringle 7668 (holotype: GH!, isotypes: ENCB!, GH!, MEXU!, US!, TEX!, VT!) .

Herb, perennial, stoloniferous, stem scapiform, slender, more or less flexuous, 15.0– 32.5 cm high, bearing 3–5 linear acute bracts between leafy base and solitary terminal head, striate or ribbed, green or slight to dark purplish, sparsely pubescent. Leaves basal, crowning the oblique rhizome, petiolate, lanceolate to somewhat obovate-lanceolate including the petiole 3–10(17.3) cm long, 0.5–3.0 cm wide, apex acuminate, acute, margin bearing 3–4 teeth or mucros on each side, gradually narrowed at the base into the slender petiole, dark green and pubescent adaxially with scattered trichomes, paler and glabrous abaxially; petioles channeled, green to reddish-purple 4.5–7.5 cm long, usually as long as or sometimes exceeding the blade. Capitulum 6–8.8 mm high, including the rays 1.5–3.4 cm in diameter; involucre campanulate, about as high as the disc florets. Receptacle convex, ca. 4.5 mm in diam, glabrous. Phyllaries 2–3 seriate, imbricate, subequal, lanceolate, acute, pubescent with scattered trichomes, green with purple apices. Radiate florets 60–90 in 2 series; corollas 7–8 mm long, tube 2.1 mm long, ligules 2 veined, 0.7 mm wide, white, drying white to tinged with reddish-purple, apex 2–3 dentate. Disc florets 160-170; corollas tubular, bright yellow, 2.94 mm long, with erect to divaricate, deltate lobes, tube 2.6 mm long, style branches 0.8–1 mm long. Cypsela narrowly oblong, compressed, 1.5 mm long, with 2 thin orange ribs, glabrous to sparsely strigose. Pappus bristles 20, in single series, 2 mm long for both ray and disc florets ( Fig. 2 ).

Phenology: —Flowering and fruiting from February to May.

Distribution: —Endemic of northern Morelos, Mexico, only known from two localities in the northwestern canyons of Cuernavaca, Morelos, Mexico ( Fig. 3 ).

Ecology and habitat: — Erigeron morelensis grows in the northwestern area of the municipality of Cuernavaca, on wet cliffs in canyons, at elevations from 1980 (historic record) to 2260 m ( Fig. 3 ). Both newly discovered localities occur in disturbed Quercus forests with cloud forest elements. Erigeron plants were growing with Adiantum sp. , Thelypteris sp. , Pteridium sp. , Erigeron karvinskianus DC. , Smilax mollis Humb. & Bonpl. ex Willd. , Oxalis sp. , Styrax argenteus var. ramirezii (Greenm.) Gonsoulin , and Carpinus caroliniana Walter. Capitula of Erigeron in the wild and cultivation were eaten by caterpillars.

Conservation status: — Erigeron morelensis was only known from specimens collected at the type locality (canyons of Cuernavaca, Morelos) in 1898. It had not been collected for more than 120 years, until the first population (present study) was observed in 2021 with approximately 25 individuals. A second population found in April 2022 comprises 250–300 individuals. It is proposed that E. morelensis should be classified as Critically Endangered (CR) using the IUCN B2 ab(iii) criteria ( IUCN 2022).

Specimens examined: — MEXICO. Morelos: Cuernavaca, wet cliffs, mountain cañon near Cuernavaca , 6500 ft, 15 May 1898, C. G . Pringle 7668 ( ENCB!, GH!, MEXU!, TEX!, US!, VT!) ; Cuernavaca, Tepeite Valley , on wet cliff, 2260 m, 19°0’N, 99°17’W, collected immature 28 July 2021, pressed 1 April 2022 (fl), M. I. Miguel V. 972 B ( HUMO) ; Chalchihuapan Canyon , steep, wet south-facing slope, 2070 m, 18°58’N, 99°17’W, 11 April 2022 (fl, fr), R. Cerros T. 3178 (HUMO) .

Figures

FIGURE 1. Erigeron morelensis Greenm. (Holotype: C.G. Pringle 7668, GH!).

FIGURE 2. Erigeron morelensis.A. Habitat with Erigeron plants indicated by white circles; B. Basal leaves with reddish to purple petioles, white arrows show immature capitula; C. Habit highlighting basal leaves and a monocephalous stem, white arrows show aboveground stolons; D. Capitula with ligules; E. Phyllaries green and purple with pink ray florets; F. Receptacle with disc and ray florets; G. Individual ray and disc florets; H. Cypsela with orange ribs (black arrow) and bristles; I. Echinate pollen grains. Photos by Rosa Cerros-Tlatilpa and Mónica I. Miguel-Vázquez.

FIGURE 3. Known geographic distribution of Erigeron morelensis Greenm.