Epidendrum petacaense Hágsater, J.Duarte & Pío-León, 2023

Hágsater, Eric, Salinas, Julian Duarte, Machorro, Rolando Jiménez, Píoleón, Juan F. & Millán Otero, Manuel G., 2023, Epidendrum petacaense, a new species of Orchidaceae from Sinaloa, Mexico, Phytotaxa 592 (2), pp. 81-87 : 82-86

Epidendrum petacaense Hágsater, J.Duarte & Pío-León , sp. nov. ( Figure 1 ).

Type:— MEXICO: Sinaloa: Municipio La Concordia, Sierra de los Bules o Agua Zarca , cerca de La Petaca, 1759 m, 23 julio 2022, J. F. Pío-León, L. A. Cárdenas & M. Pérez 349 (holotype: CIIDIR!; isotypes: AMO! MEXU! USON!) (LCDP voucher, digital images AMO!) .

Epidendrum petacaense is similar to E. vandifolium but the flowers are bright lilac-magenta, calli white (vs. flowers red to pale magenta, occasionally green, the calli red), margin of sepals and petals spreading (vs. margins revolute), lateral lobes of the lip dolabriform to flabellate (vs. lateral lobes widely rectangular, more or less rounded), mid-lobe sub-orbicular, forming a narrow isthmus at the base, bilobed, the apical lobes rounded (vs. mid-lobe oblong-cuneate), clinandrium-hood surpassing the body of the column (vs. clinandrium-hood reduced, not surpassing the column), and the ovary inflated ventrally behind the perianth (vs. ovary terete, only slightly inflated towards the apex).

Description: — Lithophytic, sympodial, caespitose, erect to arching herb, 9–35 cm tall including inflorescence. Roots 2.0–5.0 mm in diameter, fleshy, thick, green to white becoming red when wet, tinged red at apex when in growth. Stems 9–30 cm long and 0.5–1.0 cm thick, simple, cane-like, terete, thin, sub-erect to arching; base covered by tubular sheaths, non-foliar, whitish with minute black dots, striated when dry, papyraceous; frequently producing keikis from upper half of mature stems. Leaves 6–13, distributed along apical half of stems, alternate, articulate, sub-coriaceous; sheaths tubular, with minute wine-colored dots; blade 3–7 × 0.4–0.6 cm, linear-lanceolate, acute, smooth, light green, margins entire, spreading. Spathe lacking. Inflorescence 2.5–5.0 cm long, apical, erect, straight, racemose to paniculate, pluriannual, producing new racemes from old peduncles over several years; peduncle 1.2–2.0 cm long, terete, thin, straight, provided with 2–3 bracts 5–7 mm long, tubular, acuminate, embracing, gradually smaller. Floral bracts 1.5–3.0 mm long, much shorter than ovary, triangular-ovate, acuminate, embracing, gradually shorter. Ovary 11–15 mm long, terete, ventrally inflated behind perianth, furrowed. Flowers 5–7 per raceme, successive, non-resupinate, magentalilac, column totally white to magenta at base and apex white; fragrance none registered. Sepals 8–9 × 3–4 mm, free, spreading, obovate to elliptic, obtuse, 5-veined (lateral veins short branched), margins entire, spreading; lateral sepals oblique, minutely apiculate. Petals 7–9 × 2.0– 2.5 mm, obovate-oblanceolate, apex rounded, 3-veined (lateral veins short branched), margins minutely dentate, spreading. Lip 6.0–7.0 × 7.0–9.0 mm, united to column, 3-lobed, base cordate, margins erose-crenulate; lateral lobes 3.0–4.0 × 3.5–4.0 mm, dolabriform to flabellate, in some plants they overlap mid-lobe, appearing entire; mid-lobe 3.5 × 4.5 mm, sub-orbicular, forming a narrow isthmus at base, bilobed, apical lobes rounded, margin erose; bicallose, calli prominent, digitiform, divaricate; disc with 3 parallel ribs that disappear before reaching apical sinus. Column 5 mm long, short, thin at base gradually wider towards apex which is sharply bent downwards some 45°, with pair of apical rounded wings. Clinandrium-hood short, slightly surpassing body of column, margin entire; Rostellum apical, slit. Lateral lobes of stigma small, 1/3 length of stigmatic cavity. Anther reniform, 4-celled. Pollinarium formed by 4 pollinia, obovoid, laterally compressed, sub-equal; caudicles soft and granulose, as long as pollinia; viscarium semi-liquid. Nectary shallow, penetrating ¼ of pedicellate ovary, not inflated, unornamented. Capsule not seen.

Distribution and ecology: — The known distribution of the species is a single locality in pine-oak forest, on the western slope of the Sierra Madre Occidental, at an elevation of 1750 m, corresponding to the madrense-tropical region as defined by González-Elizondo et al. (2012) ( Figure 2 ). This area is close to the extreme northern range along the Pacific of the genus Epidendrum . It was found on a slope and rocky cliffs covered by bryophytes and lichens, with a northern exposure, together with Agave rzedowskiana Carrillo et al. (2003: 240) , Arbutus sp. Linnaeus (1753), Lamourouxia sp. Kunth ( Bonpland & Humboldt 1818), Muhlenbergia sp. Schreber (1789), Pitcairnia sp. L’Heritier (1789) and Rhynchospora sp. Willdenow (1809) ( Figure 3 ). It has been observed in flower from mid-July to the end of August.

Etymology: — The specific epithet is coined in reference to the locality near where the type was collected, La Petaca, in the State of Sinaloa, close to the border with the state of Durango, Mexico.

Conservation status: — DD. Data deficient. Epidendrum petacaense is only known from the type locality, an area of less than 0.5 km ². It should potentially be considered Critically Endangered, but data on populations is lacking. However, the individuals were found mainly in slopes near 90°, of difficult access and areas which are not apt for agriculture nor human habitation, so it is improbable that they are endangered by anthropogenic activity in the short and medium term.

Additional specimens examined (paratype):— MEXICO: Sinaloa: Mun. Concordia, Sierra de Los Bules o Agua Zarca , cerca de La Petaca, 1750 m, 21 August 2022, J. F. Pío-León & M. Pérez 361 (CIIDIR!) .

Other records:— Mexico: Sinaloa: Mun. Concordia, 17 July 2022, Millán-Otero s.n. (digital images, AMO!). https://www.naturalista.mx/observations/128435566

Taxonomic Discussion: — Epidendrum petacaense belongs to the Epidendrum anisatum group ( García-Cruz & Hágsater 1998), which includes sympodial, cespitose, erect plants, characterized by basal roots, very fleshy, thick forming large masses, erect stems, cane-like, terete, leaves distributed usually beyond the middle of the stems, linear to narrowly elliptic or elliptic, coriaceous, apical inflorescences, lacking any spathe at the base, racemose, rarely paniculate, and usually producing new racemes from the same peduncles in successive years thus pluri-racemose, the flowers are generally dull colored, green-yellow to red. The new species is recognized by the bright lilac-magenta flowers with the calli white, the petals 7–9 mm long, obovate-oblanceolate, the lateral lobes of the lip are dolabriform to flabellate, in some plants they overlap with the mid-lobe giving the appearance of an entire lip, the mid-lobe is suborbicular, bilobed, the disc has three thin parallel ribs that are short and disappear at the middle of the lip. It is similar to E. vandifolium Lindley (1849: 269) which also grows in the Sierra Madre Occidental in the same general area, though more widespread. The type of Epidendrum durangense Hágsater & Holman (1984: 301) , now considered a synonym of E. vandifolium ( García-Cruz 1995:145, Govaerts 2003), was found epiphytic about 40 km distant and has been found even closer. That species has reddish to pale purple flowers, sometimes green, the sepals are 10–14 mmm long, the lateral sepals descendent, the petals 9.5–11 mm long, descendent; the lateral lobes of the lip are widely rectangular, separated from the mid-lobe by deep sinuses, and the mid-lobe is oblong-cuneate, the clinandrium-hood reduced, not surpassing the body of the column. Both species in the vicinity in pine-oak forests. Epidendrum vandifolium is usually epiphytic on oaks, but occasionally also lithophytic. Epidendrum petacaense has only been seen lithophytic, in rocky slopes and cliffs. Epidendrum anisatum is distributed in the Eje Volcánico and the Sierra Madre del Sur, and has beige flowers with very small red dots, the column green, and the disc tinged wine-red, petals (6.5–) 9–12.4 (–14) mm long, narrowly spatulate; the lateral lobes of the lip elliptic to sub-orbicular, the disc provided with 3 prominent ribs, the midrib reaching the apical sinus of the lip ( García-Cruz 1995), and has a night and early morning fragrance of anisaldehyde ( Hágsater & Holman 1984: 304). Epidendrum lowilliamsii García-Cruz (1992: 132) is distributed in the Eje Volcánico Transversal, also has a prominent clinandrium-hood, surpassing the body of the column, and similarly thin stems but different narrower linear-leaves, the flowers yellow green, the lateral lobes larger than the mid-lobe, obliquely ovate, the margins irregularly dentate, and the mid-lobe oblong, emarginate (see Figure 4 , for digital images of the four species compared).

The region where the new species was discovered is very interesting for orchids, possibly also for other botanical groups ( Ávila-González et al. 2019). For several years it has been recognized that it harbors some orchids, possibly vicariants of species whose geographic range along the Mexican Pacific slope end at the limits of Jalisco and Nayarit. Northward in Sinaloa, Sonora and Durango they are replaced by morphologically similar but different species or subspecies. For example: Encyclia adenocaula (Lexarza) Schlechter (1918: 470) and E. adenocaula subsp. kennedyi (Fowlie & Withner) Soto Arenas, Salazar & Hágsater (2003: 7) , as well as Bletia parkinsonii Hooker (1839 :t.3736) and B. santosii H.Ávila, J.G.González & Art.Castro ( Ávila-González et al. 2019: 360). Hágsater & González Tamayo (1975), and Withner (1998) discuss the consistency and variation of Encyclia adenocaula and Encyclia kennedyi , with Soto et al. (2003) finally transferring the latter as a subspecies of the former. Encyclia adenocaula subsp. kennedyi is found in the same general area of the new species, and ranges south to the state of Nayarit and possibly into Jalisco (see discussion of Hágsater & González Tamayo 1975). However, E. petacaense is clearly different with usually much narrower leaves, the color of the flowers and their morphology is very distinct within the Anisatum Group.

Figures

FIGURE 1. Lankester Composite Dissection Plate of Epidendrum petacaense Hágsater, J.Duarte & Pío-León.A Habit. B. Inflorescence. C. Flower. D. Dissected perianth. E. Ovary and longitudinal section of column. F. Column, lateral and ventral view. G. Anther cap and pollinarium. Prepared by Anaís Cisneros from the images of the pretype by J.F. Pío-León.

FIGURE 2. Geographic location of Epidendrum petacaense Hágsater, J.Duarte & Pío-León. The regions of the Sierra Madre Occidental are according to González-Elizondo et al. (2012).

FIGURE 3. Habitat of Epidendrum petacaense Hágsater, J.Duarte & Pío-León. The yellow arrows indicate some of the individual plants in the natural habitat. Photographs by J.F. Pío-León.

FIGURE 4. Comparison of the four morphologically similar species. A. Epidendrum petacaense, (Pío-León 349); B. E. lowilliamsii, (García-Cruz 1245); C. E. vandifolium (Hágsater 4666, type of E. durangense); D. E. anisatum (Greenwood s.n.).