Pinus georginae

Pérez de la Rosa 2009

Common names

Pino, Pino chino (Pérez de la Rosa 2009).

Taxonomic notes

Type: Mexico, Jalisco, Municipio de Atenguillo, El Rodeo, 20.25817°N, 103.59236°W, 1520m, 2005.07.16, J. A. Pérez de la Rosa and G. Vargas Amado 1926; holotype IBUG, isotypes K, MEXU, MO, NY.

This is a member of the large and diverse subsection Australes. Prior to its description as a distinct species, specimens of P. georginae were typically assigned to P. praetermissa, a sympatric species that it closely resembles, but does not occur with. Molecular analysis has shown P. georginae to be most closely related to P. luzmariae, a sympatric species, from which it likely diverged during early Pleistocene time (Hernández-León et al. 2013, Gernandt et al. 2018).

Description

Trees, 15-20(-25) m tall and 30-35(-70) cm dbh, usually with 2 or 3 stems and a broad, rounded crown. Bark on mature trees pale to dark gray in rectangular plates. Twigs 4-6 mm thick, scaly, yellowish. Leaves in fascicles of (3-)5, sheath persistent, 15-17 mm long; leaves light green on inner and dark green on outer faces, 9-15(-19) cm long, 0.9-1 mm thick, stomata in 2-4 rows on every leaf face. Pollen cones subterminal on twigs, 16-19 × 3.3-4.4 mm. Seed cones subterminal, solitary or in pairs, with curved stalks 16-20 mm long and 4-5 mm thick, persistent, falling with the stalk and a portion of the branchlet attached (an unusual character, shared with P. praetermissa); ovoid, 6-8 × 6-7 cm, with 75-85 seed scales per cone; red-brown turning gray after opening; seeds widely triangular, dark brown, 6.5-7.3 mm long with a 15-20 mm wing. Pollination occurs in June and July; cone maturation takes two years. Seed dispersal is in March or April, and seeds commonly germinate after the first rains in June (Pérez de la Rosa 2009).

The most similar sympatric species is P. praetermissa. P. praetermissa has smooth (rather than rough) twigs, shorter (< 15 mm) fascicle sheaths, shorter (6-12 mm) pollen cones, and a pale (rather than very dark) umbo (Pérez de la Rosa 2009).

A key to the pines of Jalisco in subsection Australes is given by Pérez de la Rosa and Gernandt (2017) and would be useful in efforts to identify this species in the field.

Distribution and Ecology

Endemic to an area near the towns of Atenguillo, Cuautla and Mascota in Jalisco, within intermountain valleys at elevations of 1400-1700(-2000) m. The area averages 932 mm of precipitation with an average temperature of 21.6°C. Occurs in pine-oak forest near natural grasslands, sometimes dominant, elsewhere with P. douglasiana, P. devoniana, P. oocarpa, P. lumholtzii, P. luzmariae and oaks including Quercus resinosa and Q. obtusata. Often parasitized by the mistletoe Cladocolea cupulata (Pérez de la Rosa 2009).

Remarkable Specimens

Ethnobotany

Observations

The type locality, described above, sounds like a good place to look. Other locations are precisely stated by Pérez de la Rosa (2009).

Remarks

The epithet honors Georgina Vargas Amado, who with Pérez de la Rosa collected the type specimen (Pérez de la Rosa 2009).

Citations

Gernandt, D. S., X. Aguirre Dugua, A. Vázquez‐Lobo, A. Willyard, A. Moreno Letelier, J. A. Pérez de la Rosa, D. Piñero, and A. Liston. 2018. Multi‐locus phylogenetics, lineage sorting, and reticulation in Pinus subsection Australes. American Journal of Botany 105(4):711–725.

Hernández-León, Sergio, David S. Gernandt, Jorge A. Pérez de la Rosa, and Lev Jardón-Barbolla. 2013. Phylogenetic relationships and species delimitation in Pinus section Trifoliae inferrred from plastid DNA. PLOS One DOI: 10.1371/journal.pone.0070501.

Pérez de la Rosa, Jorge A. 2009. Pinus georginae (Pinaceae), a new species from western Jalisco, Mexico. Brittonia 61:56-61.

Pérez de la Rosa, Jorge A. and David S. Gernandt. 2017. Pinus vallartensis (Pinaceae), a new species from western Jalisco, Mexico. Phytotaxa 331(2):233-242 (p. 234).

See also