Quercus­ purhepecha ­ De Luna-Bonilla, S. Valencia & Coombes, 2024

Luna-Bonilla, Oscar Angel De, González-Rodríguez, Antonio, Rodríguez-Correa, Hernando, Piña-Torres, Javier, Coombes, Allen J. & Valencia-A, Susana, 2024, Quercus purhepecha (Fagaceae), a new species of shrub oak endemic to the state of Michoacán, Mexico, Phytotaxa 670 (4), pp. 191-202 : 195-198

Quercus­ purhepecha ­ De Luna-Bonilla, S. Valencia & Coombes sp. nov. ( Figs. 4 , 5 ).

Type:— MEXICO. Michoacán. Municipio Morelia: Carretera Morelia-Atécuaro , al lado del camino, 2240 m. 19.63º N, 101.20º, 21 September 2022, O. De Luna Bonilla & S. Morales ODL-543 (holotype FCME183410 !, isotypes HUAP! , MEXU! ) ( Fig. 6 ).

Diagnosis: — Quercus purhepecha can be confused with Q. laeta , Q. frutex , Q. microphylla and Q. repanda . From Q. laeta (a tree with toothed leaves) it can be distinguished by its shrubby, rhizomatous habit and by having both toothed and untoothed leaves. From Q. frutex it can be distinguished by its rhizomatous habit and leaves that are not or only slightly revolute. From Q. microphylla it can be distinguished by its rhizomatous habit and the presence of shortly stipitate vs. sessile fasciculate trichomes on the abaxial blade surface. From Q. repanda , which also has a rhizomatous habit, it is distinguished by its not or only slightly revolute leaves (distinctly revolute in Q. repanda ) and the lack of amber trichomes.

Description:— Shrubs rhizomatous, 0.3–0.7 m tall, twigs (1)1.3–2.3(2.7) mm in diameter, gray to pale-reddish, slightly furrowed, glabrous to tomentose, retaining sparse stipitate fasciculate trichomes, with conspicuous lenticels; buds ovoid, 2.6–3 mm long, scales broadly ovate, glabrous, reddish-brown, margin irregularly fimbriated. Mature leaves with petioles 2.3–3.4 mm long × 1.0– 1.3 mm in diameter, yellowish to slightly reddish toward the base, glabrescent with sparse whitish fasciculate stipitate trichomes, stipules linear to narrowly lanceolate 2.8–5.6 mm long, glabrescent or somewhat floccose, retaining sparse grayish sessile fasciculate trichomes, usually persistent even when leaves are mature; lamina coriaceous, slightly obovate, oblong, ovate-lanceolate, rarely ovate, 3.5–5.2(7) cm long × (1.2)1.4–2(2.5) cm wide, 2.5–3 times longer than wide, apex acute, attenuate to rounded, margin thickened, flat or slightly revolute, entire or with 1–2 short mucronate teeth, some leaves of juvenile shoots from the base of the plant or the rhizome may have up to 7 teeth almost from the base, base rounded or slightly subcordate, secondary veins (6)7– 10(12) on each side of the midvein, ascending, moderately curved towards the margin, branched and anastomosed before reaching the margin, adaxial blade surface dull, glaucous, secondary veins slightly impressed, glabrous to glabrescent, preserving scarce fasciculate trichomes laxly distributed towards the base of the lamina and midvein, abaxial blade surface whitish to grayish, tomentose to glabrescent, with fasciculate shortly stipitate trichomes with whitish crispate rays becoming dark with age, laxly distributed, not obscuring the white-papillose and somewhat bullate epidermis. Fruits annual, 1–2 on a grayish, pubescent to glabrous peduncle 0.7–2 cm long × 1.2–2.5 mm in diameter; cupules hemispheric to slightly conical, 8.3–12 mm long × 13–19 mm in diameter, scales triangular to narrow-triangular towards the margin of the cupule, base of scales keeled and white-pubescent, nuts brownish, glabrous, ovoid to oblong-ovoid, 15.5–18.3 mm long × 11–15 mm in diameter, ca. ½ their total length included in the cupule.

Distribution and ecology:— Mexico (Michoacán). Elevation 2100–2450 m. It grows at the margin of the oak forest, in patches that spread mainly rhizomatously, in poor and shallow soils; associated with Q. castanea Née (1801: 276) , Q. deserticola Trelease (1923: 79) and Erythrina leptorhiza Mociño & Sessé ex de Candolle (1825: 413) . Flowering in January and February; fruits mature in September. Some plants had numerous galls. These are caused by wasps of the genus Atrusca Kinsey (1936: 105) (Juli Pujade, pers. comm. 2024).

Preliminary conservation status:—As a result of the analysis of extent of occurrence (EOO = 42.2 km 2) and area of occupancy (AOO = 2.25 km 2) implemented by GeoCAT, the preliminary conservation status of the species would be Critically Endangered (CR). It is of noteworthy importance to point out that since the species presents vegetative propagation, it is very complicated to establish the exact number of individuals, but it can be inferred from field work that it is low. In addition, considering the low number of locations where the species was observed, and its distribution near the city of Morelia, which is experiencing rapid growth ( Cigna and Tapete, 2021), a conservation plan for the species should be considered a priority.

Etymology:—The specific epithet is dedicated to the indigenous people of the P’urhepechas who inhabit the state of Michoacán, where this species of oak is endemic.

Additional specimens examined:— MÉXICO, MICHOACÁN. Municipio Morelia: Av. Atécuaro aprox. 300 m después del km 2 ladera SE , 2144 m. 19.64258°N, 101.19885°O, 27 October 2022, O. De Luna Bonilla & S. Morales ODL-550 ( FCME) ; 2 km al SE de la Piedra del Indio sobre la montaña , 2144 m. 19.62979°N, 101.21345°O, 7 August 2021, O. De Luna Bonilla & A. González Rodríguez ODL-501 ( FCME) ; Camino a cerro del Águila aprox. a 3 km de Joya de la Huerta sobre la brecha , 2450 m. 19.61688°N 101.33292°O, 23 October 2023, O. De Luna Bonilla ODL-598 ( FCME) ; 2 km al SO del poblado Cuanajillo Grande al lado de la brecha principal , 2270 m. 19.64234°N 101.34571°O, 31 October 2023, O. De Luna Bonilla ODL-627 ( FCME) ; Cerro del Águila subiendo por Tacícuaro , 2350 m, 19°39’04”N, 101°22’00”O, 30 August 2007, G. Cornejo Tenorio et al. 2267 ( MEXU) ; Cerro del Águila subiendo por Tacícuaro , 2350 m, 19°39’04”N 101°22’00”O, 30 August 2007, G. Cornejo Tenorio et al. 2257 ( MEXU) ; Cerro del Águila, subiendo por San Nicolás Obispo , 2170 m, 19°37’52”N 101°19’53”O, 12 July 2007, E. Sánchez García et al. 95 ( MEXU) ; Lado Noreste del Cerro del Águila, subiendo por el poblado de San Nicolás Obispo , 2315 m, 19°38’06”N 101°20’24”O, 11 April 2008, E. Sánchez García et al. 573 ( MEXU) .

Notes:—Leaves on adult shoots of Quercus purhepecha can be confused with those of Q. frutex while those on vigorous, juvenile shoots can be confused with those of Q. laeta , species that are also present in the Trans-Mexican Volcanic Belt, although not in the Cuitzeo basin. In addition to the differences noted in Table 2 , from Q. frutex it is distinguished by its rhizomatous growth, as well as its smaller leaf blades (3.5–5.2(7) × (1.2)1.42(2.5) cm. Quercus frutex can also be distinguished from Q. purhepecha by its densely tomentose twigs, and lamina 1.2–4.8 × 0.7–1.5 cm. Quercus laeta is always a tree with leaf blades 6.5–9(15) × 2.4–3.7(4.5) cm. One of the most important aspects that has not been considered in the studies of shrub oaks is the general morphology and growth form (shrub type). In the case of Q. purhepecha , dense patches are composed of multiple single, thin, sparsely branched stems that grow from the rhizome, while in the case of Q. frutex , branching is generally from a single thickened stem emerging from the rhizome that branches further towards the apical zone.

Figures

FIGURE 4. A-I Quercus purhepecha. A. Mature stem emerging from the rhizome; B. Different leaf morphologies; C. Stipitate fasciculate trichomes present on the underside of the leaf; D fasciculate trichomes present on upper side of the leaf; E Detail of the thickened petiole and bud; F Female flower; G detail of rounded buds with irregularly fimbriated scales; H Mature acorns; I. General habit of an individual with detail of the rhizome. Drawn by Moises Emanuel Bernal Hernández based on ODL-543 (FCME).

FIGURE 5. A-G Quercus purhepecha. A. Multiple stems emerging from the rhizome from a burned individual; B. General appearance of the shrub, composed of multiple stems; C. Solitary individual not yet forming a dense shrub; D. Female flowers; E. Mature acorn; F. Multiple wasp galls growing on the leaves of different stems; G. Detail of the rhizome and the insertion of the stems. Photos by O. De Luna-Bonilla.

FIGURE 6. Holotype of Quercus purhepecha. Photo by Gabriela Flores-Valencia.