Pinus vallartensis Pérez de la Rosa & Gernandt, 2017

Pérez De La Rosa, Jorge A. & Gernandt, David S., 2017, Pinus vallartensis (Pinaceae), a new species from western Jalisco, Mexico, Phytotaxa 331 (2), pp. 233-242 : 234-238

Pinus vallartensis Pérez de la Rosa & Gernandt , sp. nov. ( Fig. 1 )

Type :— MEXICO. Jalisco: municipio de Puerto Vallarta, 100 m al sur de “Las Juntas” (arroyos Palo María y Chupalodo), 20°31’53.5”N, 105°14’41.8”W, elevation 423 m, 17 September 2016, J. A. Pérez de la Rosa & D. Gernandt 2134 (holotype: IBUG!; isotype MEXU!) .

Diagnosis:—Similar to Pinus oocarpa and P. jaliscana , differing in its lax leaves and smaller seed cones that range in length from (2.2–)2.5–3(–4.0) cm.

Trees (6–)8–12(–18) m, trunk 30–50 cm in diameter, generally tortuous; bark 2–4 cm thick, occasionally thicker, light gray outside and reddish-brown inside, in rectangular plates, crown ample and open, making up 1/2 to 1/4 of the total height, light green. Fascicles persisting 2–3 years, rarely more; cataphylls brown to yellowish brown, 3.6–4.2 mm × 2–2.5 mm at the base, margins hyaline and ciliate, sheaths (1.0–) 1.2–1.5 cm, yellowish brown when young, dark grey to almost black upon maturity, with 8–10 bracts. Leaves in fascicles of (3–4–)5, lax, light green, finely serrate, (12–)17–20(–22) cm × 0.8–0.9 mm with 3–4(–5) rows of stomata on the abaxial face and 2–3 on each of the adaxial faces. Pollen cones 11–27 mm × 4–6 mm, brown to yellowish brown, with the superior margin of the scales finely dentate. Seed cones ovoid, solitary or in pairs, rarely in whorls of three, (2.2–)2.5–3(–4.0) cm × (2.6–)3.1–3.5(–4.0) cm when open, on peduncles 0.8–1.8 cm × 3–5.5 mm, persistent, falling with the cone; seed scales 34–53 per cone, yellowish brown, lustrous. Seeds dark brown to yellowish brown, 5.3–7.3 mm × 3.4–4 mm, with wings 12–15 × 3–5 mm. Number of cotyledons: 4–7.

Leaf anatomy: —Epidermis thin and uniform, hypodermis irregular with interstomatal intrusions into the mesophyll reaching the endodermis; resin canals septal, 3–6 contained within the septal hypodermis, 1–3 on the abaxial face and 1–2 on each adaxial face; endodermis with ovoid cells and uniform walls, two proximal vascular bundles.

Distribution: —To date, no hard pine (subgenus Pinus ) with a more restricted population has been found in the state of Jalisco. The species is almost exclusive to the southern part of the municipality of Puerto Vallarta ( Fig. 2 ). The populations are reached by ascending paths, and have a north-south and east-west exposure. At its southern limit the species enters the municipalities of Cabo Corrientes and Talpa de Allende, from 20°32’36.5”N; 105°14’14.9”W at its northern limit to 20°28’06.9”N; 105°13’22.4”W at its southern limit; at elevations of 380–1347 m a.s.l.

Ecology: —According to the terrestrial biogeographic classification of Cuanalo de la Cerda et al. (1989), P. vallartensis occurs in the Sierra Madre del Sur terrestrial province, between the subregions Planicie Higuera Blanca (Eb6) and Sierra Talpa de Allende (Eg3), where the predominant soils are Pellic Vertisols, Vitric Andosols, Chromic Luvisols, and Eutric Nitosols; these are acidic and deep, on north facing exposures. The median temperature is 26 °C and the annual precipitation is 1200 mm ( Villalpando & García 1993). The species is associated with Muhlenbergia distichophylla (J. Presl.) Kunth (1833: 202) , which is favored by the high frequency of fires in the region. Deneven (1961) described a similar association for P. oocarpa in Nicaragua denominated sub-climax vegetation, similar to the pine savannahs of Central America. It is also associated with other tree species such as Byrsonima crassifolia (L.) Kunth (1822: 149), Quercus aristata Hooker & Arnott Walker-Arnott (1841: 444) , Q. elliptica Née (1801: 278) , Q. magnoliifolia Née (1801: 268) , and Bejaria mexicana Bentham (1839: 15) . At more humid sites such as along stream banks it occurs with Magnolia vallartensis and Clusia salvinii Donnell Smith (1903: 1) . Its distribution meets P. oocarpa at its southern limit and P. maximinoi Moore (1966: 8) and P. jaliscana near its western limit.

Additional material examined (paratypes): — MEXICO. Jalisco: municipio de Puerto Vallarta, al sur del puerto, en las lomas que están entre los arroyos “Palo María” y “Chupa Lodo”, 20°31´53.4”N, 105°14’41.6”W, elev. 380 m, 30 November 2013, Pérez de la Rosa 2092 ( IBUG!). Municipio de Puerto Vallarta, al sur del Puerto, al este de Mismaloya , 20°30’45.7”N, 105°14’54.1”W, elev. 703 m, 14 January 2014, Pérez de la Rosa 2094 ( IBUG!, MEXU!). Municipio de Puerto Vallarta , al sur del Puerto , al E de Mismaloya , Los Miradores , 20°31’19.3”N, 105°15’05.1”W, elev. 704 m, 14 January 2014, Pérez de la Rosa 2095 ( IBUG!, MEXU!). Municipio de Puerto Vallarta , al E de Mismaloya , al oeste de la parte alta de las cascadas, en el helipuerto y sus alrededores, 20°30’30.0”N, 105°14’26.8”W, elev. 446 m, 21 February 2014, Pérez de la Rosa 2105 ( IBUG!, MEXU!). Municipio de Cabo Corrientes , 3.7 km al E de Las Juntas y Los Veranos , Rancho El Coapinal , Cerro El Viguía , 20°28’28.9”N, 105°14’50.4”W, elev. 996 m, 9 March 2014, Pérez de la Rosa 2109 ( IBUG!, MEXU!). Municipio de Cabo Corrientes , Cerro “La Ocotosa”, al E de Las Juntas ” y “Los Veranos”, 20°28’37.8”N, 105°14’26.8”W, elev. 1000 m, 9 marzo 2014, Pérez de la Rosa 2113 ( IBUG!, MEXU!). Municipio de Talpa de Allende , “Las Palomas”, entre los ranchos “El Guapinole” y “Cerro Azul”, 20°28’06.9”N ; 105°13’22.4”W, elev. 1347 m, 24 August 2014, Pérez de la Rosa 2117 ( IBUG!, MEXU!). Municipio de Puerto Vallarta , al sur del puerto, aproximadamente 1 km al norte de “Las Juntas” (arroyos “Palo María” y “Chupalodo”), 20°32’36.5”N, 105°14’14.9”W, elev. 438 m, 11 January 2016, Pérez de la Rosa 2121 ( IBUG!, MEXU!) .

Local name: —”Pino”.

Phenology: —The period of pollination occurs in the months of August and September. Seeds are dispersed in March and April and germination takes place between May and June, 7–12 days after the first rain.

Etymology: —The name of this pine is in honor of the municipality of Puerto Vallarta, where the main part of the population of this species is found. It seems to be the only pine that occurs in this municipality.

Discussion:— Pérez de la Rosa (2001) reviewed herbaria throughout Mexico and found no previously collected specimens similar to P. vallartensis . The absence of the species in collections may be due to the inaccessibility of the locality. The globose shape of the ovulate cones, needle anatomy with septal resin canals, and the branchy early phases of development suggest that P. vallartensis and P. oocarpa are closely related. They belong to Martinez’s (1948) “Grupo Oocarpa”, which he classified (without providing a Latin diagnosis) in “Sección Serótinos”, a taxonomically heterogeneous assortment of hard pine species with serotinous seed cones. As circumscribed by Martínez (1948), the Oocarpa group included five hard pine taxa with symmetric, ovoid, or shortly compressed-ovoid ovulate cones, with luteate, ochre, or reddish seed scales, and a weak, elongated, and thin peduncle. Pinus subsection Oocarpae Little & Critchfield (1969: 15) was erected for seven species colloquially described as the egg-cone pines. Farjon & Styles (1997) and Price et al. (1998) transferred additional species to Pinus subsection Oocarpae , although their circumscriptions differed markedly. Price et al. (1998) further divided the subsection into the informal “Oocarpa group”, with seven species and two varieties, and the “Teocote group”, with two species and one additional variety. With the addition of P. vallartensis , we recognize 16 species and two additional varieties for the Oocarpa group ( Table 1). Ten of these species occur naturally in Jalisco.

Taxon Distribution

Pinus chihuahuana Engelmann (1848: 103) . Mexico and southwestern United States Pinus georginae Pérez de la Rosa (2009: 56) Western Mexico

Pinus greggii Engelm. ex Parlatore (1868: 396) Northeastern Mexico

Pinus greggii var. australis Donahue & Lopez Upton (1999: 1092) Eastern Mexico

Pinus herrerae Martínez (1940: 76) Western Mexico

Pinus jaliscana Pérez de la Rosa (1983: 290) Western Mexico

Pinus lawsonii Roezl ex Gordon (1862: 64) Mexico

Pinus leiophylla Schiede ex Schlechtendal & Chamisso (1831: 354) Mexico

Pinus lumholtzii Robinson & Fernald (1894: 122) Western Mexico

Pinus luzmariae Pérez de la Rosa (1998: 127) Western Mexico

Pinus oocarpa Schiede ex Schlechtendal (1838: 491) Mexico and Central America

Pinus patula Schiede ex Schlechtendal & Chamisso (1831: 354) Eastern and southern Mexico

Pinus patula var. longipedunculata Loock ex Martínez (1948: 333) Southern Mexico

Pinus praetermissa Styles & McVaugh (1990: 310) Western Mexico

Pinus pringlei Shaw (1905: 211) Mexico

Pinus tecunumanii Eguiluz & J.P. Perry (1983: 4) Southern Mexico and Central America Pinus teocote Schiede ex Schlechtendal & Chamisso (1830: 76) . Mexico

Pinus vallartensis Pérez de la Rosa & Gernandt Western Mexico

Plastid DNA studies did not recover Pinus subsection Oocarpae or other more narrowly circumscribed subsections or groups as mutually monophyletic, leading Gernandt et al. (2005) to merge Pinus subsection Attenuatae Van der Burgh (1973: 93 ; the California closed coned pines), Pinus subsection Leiophyllae Loudon (1844: 2273) , and Pinus subsection Oocarpae into a more broadly defined Pinus subsection Australes Loudon (1844: 2255 ; the southern yellow pines). Pinus subsection Australes in turn was included in the “North American hard pines” of Pinus section Trifoliae Duhamel (1755: 126) together with subsections Contortae Little & Critchfield (1969: 15) and Ponderosae Loudon (1844: 2243). The concept of Pinus subsection Australes in this broader sense not only includes the species from the eastern United States and Antilles (subsection Australes s.s.), but also those of western North America (the Attenuatae ) and the southwestern United States through Mexico and Central America (the Oocarpae and Leiophyllae ).

Pinus subsection Australes is the largest subsection in the genus, comprising some 30 species. Further plastid DNA studies have verified the paraphyly of Pinus subsects. Attenuatae and Australes ( Parks et al. 2012; Hernández León et al. 2013), but nuclear DNA studies are also under way to corroborate the plastid results and to more conclusively establish whether the Oocarpa group is monophyletic. At present, the Oocarpa group, or the Oocarpae , is an appealing descriptive name for the serotinous egg-cone pines (including the Leiophyllae ) naturally distributed in the southwestern United States, Mexico, and Central America.

Despite the similarity between P. vallartensis and P. oocarpa , the newly-described species can be recognized without difficulty by its diminutive ovulate cones and cataphylls. Sixteen cones taken randomly from several trees had an average length of 2.84 cm and a width of 3.15 cm. They can also be distinguished by the diameter of the shoots (they are thinner) and their flaccid foliage. A third species in the Oocarpa group, P. jaliscana , borders P. vallartensis to the west and shares the disposition of its septal resin canals, but is easily distinguished by its oblongly-conical cone shape, thicker needles, and different pollination periods ( Table 2). Another similar species, P. praetermissa Styles & McVaugh (1990: 310) , has a distribution confined to Jalisco, Nayarit, and Sinaloa. It is distinguished readily from P. vallartensis by its leaf resin canals in an internal or medial position; its cone peduncles from 1.5–4.0 cm long compared to no greater than 1.8 cm in P. vallartensis ; and its larger cones, measuring (4–)5–6.5(–7) cm × (5–) 6–8 cm, that upon maturation usually lose a few basal scales ( Farjon & Styles 1997; Pérez de la Rosa 2009).

Farjon & Styles (1997) mention that although variable, the number and principally the position of the leaf resin canals can be used as diagnostic characters in Pinus . Most Mexican species have a “primary” position and occasionally one or very few canals in another position, referred to as “subsidiary”. Depending on their position they have been described as external, medial, internal, or septal. The only species in Mexico with septal resin canals are P. oocarpa , with a wide distribution in the country (according to Styles [1993] it is the most widely distributed tropical species in the world); P. jaliscana , endemic to the state of Jalisco; and now, P. vallartensis , also endemic to Jalisco, with a limited distribution in the Sierra Madre del Sur. The characters that distinguish these three taxa are summarized in Table 1. The cones and seeds of the three species with septal resin canals are compared in Fig. 3 .

Conservation status: —The area of distribution extends across only a few square kilometers, mainly in the southern part of the municipality of Puerto Vallarta, but also in a small portion of the municipalities of Cabo Corrientes and Talpa de Allende. The habitat generally is open grassland, which makes it difficult to find dense forests due to the frequent incidence of fires, both natural and provoked by humans to promote the presence of grasslands for cattle grazing. At present we estimate that the number of mature individuals is fewer than 2,500, although more field exploration is needed. Its restricted distribution, occurring in a rugged terrain with difficult access, is comparable to that of two pinyon pines endemic to Mexico, Pinus culminicola Andresen & Beaman (1961: 437) and P. maximartinezii Rzedowski (1964: 17) . These two species are listed as Endangered by the International Union for the Conservation of Nature ( IUCN 2016) and in the Norma Oficial Mexicana NOM-059 ( SEMARNAT 2010). Similarly, because of its low population densities, highly restricted geographic range (as far as its known), and proximity to human activities that may decrease its population size, we estimate that it fulfills IUCN ver. 3.1 (2016) criteria EN B1ab(ii,iii,iv,v)+2ab(ii,i ii,iv,v) and thus recommend that P. vallartensis be treated as an endangered species.

Figures

FIGURE 1. Pinus vallartensis sp. nov., A, seed cone, B, leaves, C, branch with leaves and pollen cones D, lateral view of cone scale, E, abaxial view of cone scale, F, adaxial view of cone scale, G, seeds with articulate wings. (Illustration by Gretchen Rodríguez, from J. A. Pérez de la Rosa & D. Gernandt 2134 in MEXU).

FIGURE 2. Distribution map for Pinus vallartensis in western Mexico.

FIGURE 3. Photographs of three pines from the Oocarpa group with septal resin canals, A, Pinus jaliscana seed cone (J.A. Pérez de la Rosa 1841), B, Pinus oocarpa seed cone (D.S. Gernandt 560), C, Pinus vallartensis seed cone (J.A. Pérez de la Rosa s.n.), D, Pinus jaliscana seed (J.A. Pérez de la Rosa 1841), E, Pinus oocarpa seed (D.S. Gernandt 560), F, Pinus vallartensis seed (J.A. Pérez de la Rosa s.n.). Bar = 1 cm. (Photos by D.S. Gernandt).