Graptopetalum kristenii Etter, A.Vázquez & Rosales, 2022

Etter, Julia, Vázquez-García, J. Antonio & Rosales-Martínez, C. Santiago, 2022, Graptopetalum kristenii (subg. Glassia, Crassulaceae), a new haplostemonous species from Michoacán, Mexico, Phytotaxa 555 (2), pp. 136-146 : 140-144

Graptopetalum kristenii Etter, A.Vázquez & Rosales sp. nov. Figs. 3–5 .

Type: — MEXICO. Michoacán: municipality of Coalcomán, SW of San Acamitán, shady cliffs along Río Coalcomán in tropical deciduous forest, 20 March 2013, J. Etter & M. Kristen 3764 (Holotype IBUG!; isotype CIMI!) .

Diagnosis: — Graptopetalum kristenii is similar to G. pentandrum , but it differs from the latter in rosette diameter 3.4–5.0 vs. 6.0–8.0 cm; leaf broadly oblong vs. obovate; basal branch with fewer flowers than in the rest of branches vs. with an overlapping number of flowers with respect to the rest of branches; flower diameter 12.5–15.0 vs. 17.0–19.0 mm; petal width 2.2–2.6 vs. 1.7–1.8 mm; and petal color pattern white with conspicuous red stains along vs. white to yellowish, with a rhomboid dark red stain in the upper half of the petal.

Description: —Plants perennial, caulescent, cespitose-ramose, sometimes forming dense groups, branching basally and rarely from the upper parts of the stem, 8.0–30.0 cm tall without scape; stems 2.5–3.5 mm in diam. at the base, erect at first, later decumbent to pendant, surface smooth, green-brownish to grayish, pinkish to green-glaucous from a short segment below the rosette upwards, with prominent, circular, green-brownish scars, 1.0– 1.5 mm in diam., the tips grayish; rosettes terminal, 4.0–8.0 × 3.4–5.0 cm, sometimes with somewhat scattered leaves but compact to the apex; leaves 15–30 per rosette, 1.4–2.7 × 0.7–1.3 cm, broadly oblong, straight to sometimes incurved, shortly acuminate, base obtuse, apex with a small mucro 1–2 × 1–1.5 mm, usually inclined upwards, adaxially slightly concave, abaxially convex, 4.0– 4.5 mm thick, the thickest part near the middle, greenish to glaucous-pinkish, sometimes with a different darker pinkish to purplish tonality towards the apex, somewhat pruinose, glabrous; inflorescence a paniculate cyme, 19.0–28.0 cm long; peduncle 2.0– 2.5 mm thick at the base, gray-bluish to pinkish; peduncle bracts oblong-obovate or lanceolate to elliptic, the basal 10.0–13.0 × 4.0–7.0 mm, gradually smaller upwards to 4.0–7.0 × 2.0–4.0 mm, those below the branches 2.0–4.0 × 1.0–2.0 mm; fertile part with 3–4 primary branches, with 15–24 flowers per inflorescence; primary branches 2.0–6.0 cm, with irregularly scattered bractlets, somewhat zig-zag shaped, the basal usually simple, with 3–4 flowers, the rest mostly bifurcate, with 4–7 flowers each; pedicels variable in length, 6.0–11.0 mm long, same color as the peduncle or reddish; flowers pentamerous, 12.5–15.0 mm in diameter; sepals subequal, 2.4–2.7 mm long, lanceolate, same color as the leaves; petals subequal, forming a 2.4–2.9 mm long tube, the lobes 4.9–6.2 × 2.2–2.6 mm at the widest part near the base, triangular, shortly acuminate, bending back, white with conspicuous red stains along, with a shallow middle-groove along; stamens 5, antesepalous, ca. 6.0–7.0 × 0.3–0.5 mm, erect at first, later curving outside, white-pinkish, reddish in the upper half, base adnate to corolla tube; anthers rounded, white; gynoecium protruding from the corolla, ca. 6.0–7.0 × 3.5 mm, creamish-yellow to yellow-greenish, obovate, carpels abaxially obtuse; styles ca. 1 mm long, erect, reddened.

Distribution and ecology: —So far, Graptopetalum kristenii is known only from a single population in the Sierra de Coalcomán, Michoacán. It grows in tropical deciduous forest on rocky vertical slopes along a small portion of the Río Coalcomán at an elevation between 700–800 m with Agave andreae , Anthurium halmoorei Croat (1983: 301) , Bursera spp. , Epidendrum ciliare Linnaeus (1759: 1246) , Mammillaria sp. , Oncidium leleui Jiménez-Machorro & Soto-Arenas (1990: 58) , Opuntia sp. , Philodendron warszewiczii K.Koch & C.D.Bouché in Braun et al. (1855: 4), Pittocaulon hintonii Robinson & Brettell (1973: 452) , Pseudobombax sp. , Selenicereus murrillii Britton & Rose (1920: 206) , Tillandsia spp. , and others.

Phenology: —The development of the inflorescences starts to be evident during the first pair of months of the year. The anthesis occurs between early March and early April.

Eponymy: —The specific epithet honors Martin Kristen, an outstanding explorer, horticulturist, and succulent expert, whose work contributed to the discovery of some new species of Asparagaceae and Crassulaceae , including the one described here.

Conservation status: —We assessed the new species as critically endangered (CR) based on the criteria B1ab. The Extent of Occurrence was 10.0 km 2 and the Area of Occupancy was 4.0 km 2. A population reduction is expected due to deforestation for agriculture and due to climate change, which could cause more severe natural disasters and alter the microclimate of this fragile habitat. Also, the species is known from a single population within an area of less than 10 km 2.

Figures

FIGURE 3. Graptopetalum kristenii. A. Broadly oblong leaf. B. Plant with inflorescence. C–D. Flower. E. Flower bud.

FIGURE 4. Graptopetalum kristenii in habitat. A–C. Pendant rosettes growing on cliffs. D. Flowering plants. E–F. Cliffs along Río Coalcomán. Photographs by J. Etter and M. Kristen.

FIGURE 5. Graptopetalum kristenii. A. Colony showing various rosettes with inflorescence. B. Comparison between leaves and flowers of G. kristenii (left) and G. pentandrum (right). C–D. Flowers with different petal color patterns. E. Comparison between rosettes of G. kristenii and G. pentandrum. F. Branch segment with flowers and buds. G. Flower with measurements (mm). H. Leaf with measurements (mm). Photographs by J. Etter and M. Kristen.