Thursday, June 30, 2016

[Botany • 2014] Hechtia flexilifolia, H. huamelulaensis & H. nivea • Three New Species and Growth Patterns in Hechtia (Bromeliaceae: Hechtioideae) from Oaxaca, Mexico



ABSTRACT
Three new species of Hechtia from the Mexican State of Oaxaca are herein proposed as new: Hechtia flexilifolia, H. huamelulaensis, and H. nivea, from the physiogeographical provinces of Mixteca Alta, Costas del Sur, and Sierras Centrales de Oaxaca respectively. All three species are described and illustrated. Iconography provided features plants in habitat and under cultivation. An assessment of their conservation status sensu IUCN criteria is presented as well. We also discuss and illustrate the three growth patterns identified at this time in the genus.

Keywords: Diversity, endemism, growth patterns, IUCN, Oaxaca, physiogeographical regions


Hechtia flexilifolia I. Ramírez & Carnevali, spec. nov. 
This new species is characterized by an unique combination of characters: leaves numerous, (20–)30–40 in number, proportionally long, narrow, flexible, margins densely spinose, abaxial epidermis glossy and wrinkled, shedding when dry, staminate inflorescence a 1–2 times divided panicle, with a long peduncle, branches at first secund, then horizontal, branches densely flowered, cylindrical, rachis green, sulcate, sterile bases of branches bracteate, petals white.

Distribution and habitat:— Hechtia flexilifolia is known from a restricted geographical area near the village of Yosondúa, where it grows in close sympatry with H. nuusaviorum Espejo & López-Ferr. in Espejo et al. (2007b: 98). There it grows as a lithophyte on steep or vertical rock walls, at an elevation of ca. 1970 m, surrounded by humid forest. Most collections have been made from around the Yosondúa waterfalls, a well-known touristic site.

Etymology:— The specific epithet refers to the flexible foliar blades, an unique feature in the genus in Oaxaca since the rest of the species have succulent, rigid, inflexible leaves.

IUCN Conservation assessment:— Vulnerable (VU). Hechtia flexilifolia meets criteria D2 of the IUCN (2010). The species is known from an area of less than 2 km2 within which it occurs only at a handful of small sites. Albeit local populations of the species can be rich in individuals and are often inaccessible, they are widely dispersed and isolated on the slopes and cliffs of the mountainous landscape.



Hechtia huamelulaensis I. Ramírez & Carnevali, spec. nov. 
 A species similar to Hechtia glauca but leaves dull matte green (vs. glaucous), the leaf margins not undulate (vs. undulate throughout), without tufts of hairs in axils of spines (vs. with tuft of hairs in axils of spines); peduncle of the pistillate inflorescence 20–23 cm long (vs. 40–75.5 cm long); staminate sepals 2.5–3.4 mm long (vs. 1.6–2.2 mm long), pistillate floral bracts longer (2.4–4.7 mm vs. 1–2.3 mm long); fruits ellipsoid, not pendulous, 9–12.3 x 4.5–5.7 mm (vs. ovoid, pendulous, (8)9–12 x 3.5–5 mm).

Distribution:— Hechtia huamelulaensis occurs in the southeastern area of the State of Oaxaca (Fig. 3), on the Pacific slopes of the Tehuantepec Isthmus, an area belonging to the Costas del Sur Physiogeographical Province (Cervantes-Zamora et al., 1990). So far it is only known from the vicinity of the village of San Pedro Huamelula in the municipality of the same name. The area where this species has been found coincides with a relatively small patch of hot arid climate (type BSo(h’)w), which is embedded within a more extensive region of tropical subhumid climate (García 1998). At this single locality, H. huamelulaensis grows in xerophytic vegetation at an elevation of ca. 60 m and is associated with such other plants as Agave ghiesbreghtii Lemaire ex Jacobi (1864:545), Plumeria rubra Linnaeus (1753: 209), Opuntia decumbens Salm-Reifferscheid-Dyck (1834: 361), and a laxly-flowered form of Hechtia rosea.

Etymology:— The epithet refers to the locality where the new species was collected, San Pedro Huamelula in Oaxaca, Mexico.

IUCN Conservation assessment:— Vulnerable (VU). Hechtia huamelulaensis meets criteria D2 of the IUCN (2010). The species is known from an area of less than 2 sq.km. within which it occurs only at a handful of small sites. Albeit local populations of the species can be rich in individuals and are often inaccessible, they are widely scattered and isolated on the slopes and tops of small rocky hills.


Hechtia nivea I. Ramírez & C. F. Jiménez, spec. nov. 
 This new species is similar to Hechtia nuusaviorum in its inflorescence architecture and condensed, conical or cylindrical branches in both sexes; however the new species differ in that foliar blades are 21–39 x 1.3–2.9 cm (vs. 30–75 x 1.5–4.5 cm), densely white lepidote on both surfaces (vs. glabrous above and white lepidote abaxially); staminate inflorescences are denser, featuring ca. 12 branches in a rachis of 20 cm length (vs. 5 branches in the same length), branches 1.2–3 × 1–1.4 cm (vs. 4 cm long × 2.5 wide), primary bracts much longer than or equaling the branch length (vs. always shorter than the branches); pistillate inflorescences are denser with ca. 16 branches in 20 cm length (vs. ca. 5), primary bracts vary from shorter to longer than the branches (vs. always shorter), branches are cylindrical, and up to 2.4 cm long (vs. 3 cm long and spheroid), floral bracts are equaling the flower, petals green, ovary reddish, and stigma white (vs. floral bracts shorter than the petals, petals white, ovary and stigma white in H. nuusaviorum).


Distribution and habitat:— Hechtia nivea is known from a restricted geographical area in the vicinity of the village of San Pedro Nodón. It grows as a lithophyte on vertical walls where rosettes resemble silver stars from afar. It also grows at the foothills in a general area of low caducifolious forest along with species of Agave Linnaeus (1753: 323) (Agavaceae), Brahea Martius (1838: 243) (Arecaceae), Cnidoscolus Pohl (1827: 56) (Euphorbiaceae) and Bursera Jacquin ex Linnaeus (1762: 471) (Burseraceae), at elevations of about 1700 m. Hechtia nivea was collected in bloom during April 2013 and several plants of it are currently under cultivation.

 Etymology:— The specific epithet refers to the white indumentum of the leaves lending the plant a snowy aspect.

IUCN Conservation assessment:— Vulnerable (VU). Hechtia nivea meets criteria D2 of the IUCN (2001). The species is known from an area of less than 2 sq.km. within which it occurs only at a handful of small sites. Albeit local populations of the species can be rich in individuals and are often inaccessible, they are widely scattered and isolated on the slopes and tops of small hills where they are susceptible to fires and other anthropogenic disturbances.


Ivon Ramirez, Carlos F. Jiménez, Germán Carnevali and Juan Pablo Pinzón. 2014.  Three New Species and Growth Patterns in Hechtia (Bromeliaceae: Hechtioideae). Phytotaxa. 178(2):113.  DOI: 10.11646/phytotaxa.178.2.3


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