Beaucarnea olsonii V. Rojas & L.O. Alvarado, 2016

Rojas-Piña, Vanessa & Alvarado-Cárdenas, Leonardo O., 2016, Beaucarnea olsonii (Ruscaceae), a new species of ponytail palm from southwestern Puebla, Mexico, Phytotaxa 286 (1), pp. 13-22 : 15-19

publication ID	https://doi.org/ 10.11646/phytotaxa.286.1.2
persistent identifier	https://treatment.plazi.org/id/03D487AD-FFE6-0325-FF0A-5AFFE3CCEAE0
treatment provided by	Felipe
scientific name	Beaucarnea olsonii V. Rojas & L.O. Alvarado
status	sp. nov.

Treatment

Beaucarnea olsonii V. Rojas & L.O. Alvarado View in CoL , sp. nov., Figs. 2–5 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5

Type:— MEXICO. Puebla. Carr. Izúcar-Acatlán, 1297 m, 28 September 2006, M. Olson, A. Cervantes & K. Olsen 1044 (Holotype MEXU!, Isotypes MEXU!, MO!).

Beaucarnea olsonii is similar to B. hiriartiae L. Hernández (1992: 25) in its height, gray bark, and general appearance, but differs from B. hiriartiae in its tessellated bark, which is smooth or nearly smooth in B. hiriartiae . The new species also differs from B. hiriartiae in its straight leaves, which are recurved in B. hiriartiae , and in its short style, which is elongate in B. hiriartiae . The new species is easily distinguished from other Beaucarnea species by its pedicel articulation that occurs at 2/3 of the length of the pedicel below the flower, and by its considerably larger stigma. Finally, the new species is easily distinguished by its swollen base that abruptly tapers into a slender stem.

Description:—Plants arborescent, hermaphroditic, dioecious, 3–5 m tall, with massively swollen bases, 2.4–4.0 m in diameter, abruptly tapering into few slender branches ( Figs. 3A View FIGURE 3 and 5A View FIGURE 5 ). Bark gray and squamose forming irregular grooves along the length of the stem ( Figs. 3B View FIGURE 3 and 5C View FIGURE 5 ). Branches 1.0–3.0 m long, branching pseudodichotomous ( Figs. 3A View FIGURE 3 and 5A View FIGURE 5 ). Leaves perennial, 60–85 cm long, 0.9–1.7 mm wide at the middle, ensiform, rosulate, terminal, green to bluish glaucous green, straight and terminally erect ( Fig. 2 View FIGURE 2 , 3C View FIGURE 3 , 5A View FIGURE 5 ), canaliculate, with minute papillae over the stomatal grooves, margin slightly irregular, without denticles or with denticles not persistent ( Fig. 3D View FIGURE 3 ), base triangular to widely triangular ( Figs. 2 View FIGURE 2 , 3C View FIGURE 3 ). Inflorescence a thyrse, branching orders primary, secondary, and tertiary, the apical branches only with primary and secondary orders, decreasing in size acropetally ( Fig. 2 View FIGURE 2 , 3E–F View FIGURE 3 ), last unit of the inflorescence a reduced rhipidium ( Fig. 3G View FIGURE 3 ). Inflorescence bracts narrowly triangular to triangular, apex acuminate to long caudate, decreasing in size acropetally ( Figs. 2 View FIGURE 2 and 3F View FIGURE 3 ). Bracts subtending rhipidia ovate to widely ovate, papyraceous, margin premorse, 2.0–4.0 mm long ( Fig. 3G View FIGURE 3 ). Bracteoles per flower 1, enclosing the subtending flowers, obovate to widely obovate, apex obstuse, papyraceous, margin crenate. Pistillate flowers (inmature) ( Figs. 3H View FIGURE 3 , 4A View FIGURE 4 ), 3 per node; pedicels 4.0–5.0 mm long, articulated at 2/3 of the length of the pedicel below the flower ( Fig. 4A View FIGURE 4 ); perianth segments 6, basally fused, imbricate, ovate, whitish, papyraceous, midvein evident, 1.5–1.7 m long, 1.3–2.0 mm width ( Fig. 3H View FIGURE 3 ); ovary superior, pyriform, 3-lobed, 3-carpellar ( Figs. 3 H–I View FIGURE 3 and 4C View FIGURE 4 ), unilocular, septa fused basally, ovules 3–6, 1–2 per carpel, placentation basally axillar; style short or absent ( Figs. 3I View FIGURE 3 and 4C View FIGURE 4 ); stigma sessile, conic and prominent (0.4–0.5 mm long), 3-lobed, with minute single-celled papillae, each lobule pyriform ( Figs. 3I View FIGURE 3 and 4C View FIGURE 4 ); staminodes 6, epipetalous ( Fig. 3H View FIGURE 3 ). Staminate flowers not seen. Capsules (immature) obovate, 3-winged, 7–9 mm long; style 1.5 mm long; apical notch 1.0– 1.5 mm long ( Figs. 3 J–L View FIGURE 3 and 4E View FIGURE 4 ). Seeds 1 per fruit, immature, brown, testa rugose.

Habitat:—In the one known locality, Beaucarnea olsonii grows in dense tropical deciduous forest on steep slopes, associated with Acacia Miller (1754a: 15) , Agave Linnaeus (1753: 323) , Bursera Jacquin ex Linnaeus (1762: 471) , Cephalocereus Pfeiffer (1838: 142) , Cnidoscolus Pohol (1827: 56) , Comocladia Browne (1756: 124) , Croton Linneaus (1753: 1004) , Cyrtocarpa Kunth (1824: 19) , Dioon Lindley (1843 : misc. 59), Ferocactus Britton & Rose (1922: 123) , Gonolobus Michaux (1803: 119) , Hechtia Klotzsch (1835: 401) , Ipomoea Linnaeus (1753: 159) , Lonchocarpus Kunth (1824: 300) , Lysiloma Bentham (1844: 82) , Manihot Miller (1754b : s/n), Plumeria Linnaeus (1753: 209) , and Pouzolzia Gaudichaud (1826: 503) , among others, at elevations above 1200 m, in the southwest of Puebla ( Fig. 6 View FIGURE 6 ). This new taxon increases the number of species of Beaucarnea to 13 species, 4 of which occur in Puebla. With the addition of this new species, Mexico now has 10 endemic Beaucarnea species.

Distribution:— Beaucarnea olsonii is known only from the type collection in the municipality of Izúcar de Matamoros, southwestern Puebla, Mexico ( Fig. 6 View FIGURE 6 ).

Etymology:—The species epithet honors our colleague and friend Dr. Mark E. Olson, researcher at the Instituto de Biología, UNAM, who collected this species during a field trip. He has devoted his life to the investigation of the evolution of plant morphological diversity, especially to life forms or habits in the dry tropics.

Phenology:—Flowering and fruiting only known from September.

Conservation status:— Beaucarnea olsonii is a very restricted species, known only from the type locality in SW Puebla, and with an extent of occurrence estimated to be less than 100 km 2. We found few mature individuals (≈ 25) and even fewer young plants (1 seedling). Local people confirm that the plant is very rare. The type locality is surrounded by human settlements and agricultural fields, and we observed evidence of grazing and small fires set by people. There are relatively few patches of intact forest nearby suitable for the species. Given its probable extreme rarity, and that Beaucarnea species in general are ruthlessly collected for the horticultural trade ( Cardel et al. 1997), we suggest this species should be added to the category of critically endangered (CR A2cd+3cd; B1a; C2a(i)), according to the IUCN (2012).

Taxonomic remarks:— Beaucarnea olsonii is morphologically most similar to B. hiriartiae in its general size and morphology ( Fig. 5 A–B View FIGURE 5 ). The two are readily distinguished because in the new species the base is considerably wider than in B. hiriartiae , and tapers abruptly into few, slender branches, whereas in B. hiriartiae the base is taller and conical and usually branches only above a relatively slender trunk ( Fig. 5 A–B View FIGURE 5 ). In addition, in B. olsonii the bark is thicker and with markedly deeper furrows than in B. hiriartiae ( Fig. 5 C–D View FIGURE 5 ). The leaves in B. olsonii are straight and terminally erect, whereas in B. hiriartiae they are slightly more drooping ( Fig. 5 A–B View FIGURE 5 ). The general morphology of the ovary in B. olsonii is similar to the rest of Beaucarnea species, with 3 carpels, one locule, 3 wings, and septal walls fused basally. However, B. olsonii differs from the rest of Beaucarnea species in its prominent 3-lobed cubic stigma ( Fig. 4C View FIGURE 4 ). Also, B. olsonii has a long pedicel, similar to that of B. hiriartiae , but the articulation in B. olsonii occurs at 2/3 of the length of the pedicel below the flower, whereas in B. hiriartiae it occurs around the middle ( Fig. 4 A–B View FIGURE 4 ). Moreover, the apical notch of the fruit in B. olsonii is evident, whereas in B. hiriartiae , the wings cover the apical notch ( Fig. 4 E–F View FIGURE 4 ) Table 1.

Additional specimens examined (paratypes):— MEXICO. Puebla. Mun. Izúcar de Matamoros, entre la desviación a La Noria y la desviación a Ahuehuetitla, 1305 m, 22 April 2015, V. Rojas, M. E. Olson, F. Vergara y D. Burton 57–61 (MEXU).

M	Botanische Staatssammlung München
A	Harvard University - Arnold Arboretum
K	Royal Botanic Gardens
MEXU	Universidad Nacional Autónoma de México
MO	Missouri Botanical Garden