Sommera cusucoana Lorence, D. Kelly & A. Dietzsch, 2015

Lorence, David H., Dietzsch, Anke C. & Kelly, Daniel L., 2015, Sommera cusucoana, a new species of Rubiaceae from Honduras, PhytoKeys 57, pp. 1-9 : 1-3

Sommera cusucoana Lorence, D. Kelly & A. Dietzsch sp. nov. Figures 2 , 3 , 4

Type.

Honduras. Prov. Cortes, W of San Pedro Sula. El Cortecito campsite (near left bank of river), Parque Nacional El Cusuco, Sierra de Merendón, UTM 361834 1716534 + 11 m, 1333 m alt., 5 July 2013, D. L. Kelly, A. C. Dietzsch & W. Lopez 15079 (Holotype TEFH!, Isotypes MO and TCD).

Diagnosis.

Differs from its congeners by the combination of large, obovate leaves with long red petioles, glabrous or glabrate intervenal areas, red stipules, inflorescences 2-4-flowered, sparsely pubescent, with red axes, flowers with red hypanthium and calyx, and mature fruits dark red with long pedicels.

Description.

Tree 10 m high, branchlets 5-6 mm in diam., glabrous, finely ribbed when dry, with sparse, pale +/- ellipsoidal lenticels. Leaves opposite, blades 21.5-30 × 10.2-15 cm, obovate, acuminate, finely pointed, cuneate and +/- asymmetrical at base, drying membranaceous, glabrous above, strigillose beneath on costa and 2°-4° veins, intervenal areas glabrous, 2° veins 13-14 pairs, eucamptodromous, venation prominulous; petioles 4.5-9 cm long, sparsely strigillose, red when fresh; stipules narrowly deltate to lanceolate, 3-3.8 cm long, when fresh red with thin white margins, glabrous, caducous. Inflorescences 5.5-6.5 × 3-7 cm, dichasial, 2-3-4-flowered, axes sparsely strigillose, red when fresh; peduncle 2.5-3.8 cm long, bracts oblong-elliptic, c. 1 mm long, caducous; pedicels 1-2.8 cm long, with bract scars medially. Flowers with hypanthium 5 × 3-4 mm, turbinate to obovoid, glabrous; calyx limb red, cupuliform, 2-3 mm long with the tube 0.6-1 mm long, externally glabrous, lobes 5, 1-1.2 × 2 mm, broadly triangular, obtuse, equal, margins densely ciliolate; corolla cylindrical-funnelform, yellowish-cream, fleshy, tube 10-11 × 2.8-3 mm, externally densely hirtellous-tomentose, lobes 5, 1.5 × 3 mm, triangular-ovate, densely papillose-puberulent internally; anthers, style and stigmas not seen. Fruits 12-15 × 9-13 mm, subglobose to broadly ellipsoid, dark red at maturitiy, glabrous. Seeds numerous, 1-1.8 mm long, irregularly polygonal-angulate, testa dark brown, reticulate. (Figures 3 , 4 ).

Habitat and ecology.

Only two individual trees were located, about the same size and within a few meters of each other. The site is within Cusuco National Park, in the upper slopes of the Sierra del Merendón. These upper slopes (highest point 2242 m) are largely covered by montane rain forest vegetation. The bedrock is composed of a mixture of gneiss and schist ( The Nature Conservancy et al. 1994); slopes are steep and soils are strongly acidic (D.L. Kelly & A.C. Dietzsch, unpublished data).

The type locality, at 1333 m, is at the bottom of a deep, narrow valley, about 25-50 m from the bank of a small river. The site is riparian rain forest, dominated by tall trees, mainly Liquidambar styraciflua L. and Cedrela odorata L. The microclimate is moist and the vegetation lush and species-rich. The vicinity shows minor levels of disturbance: human disturbance due to the proximity of a seasonal camp-site with radiating trails, and natural disturbance due to wind-throw, and land-slips on the steeper slopes.

Etymology.

The name honors the Cusuco National Park in which it was found.

Discussion.

Sommera cusucoana differs from its Mesoamerican congeners by the combination of large, obovate leaves with long red petioles, glabrous or glabrate intervenal areas, red stipules, lax, sparsely pubescent 2-4-flowered inflorescences with red axes, flowers with red hypanthium and calyx, and long flowering and fruiting pedicels. Floral hypanthia and fruits of Sommera cusucoana are bright red at all developmental stages. Herbarium label notes for other Sommera species indicate fruits are green when immature and ripen red, at least in Sommera chiapensis , Sommera donnell-smithii and Sommera montana , and possibly white in Sommera grandis (Mexico). Only Sommera chiapensis Brandegee (Chiapas, Guatemala, Honduras) has flowers with similarly short, broadly triangular calyx lobes 1-2 mm long, but it differs in having shorter petioles 2-5 cm long, cymes with (4-)6-12 flowers, shorter corollas with tube 4-8 mm long, and smaller fruits 5-9 mm in diameter.

Figures

Figure 2. Scan of Holotype specimen of Sommera cusucoana (to be deposited at TEFH).

Figure 3. Sommera cusucoana. A Tip of shoot with infructescence and leaf pair emerging between pair of stipules. Note red color of stipules, petioles, and infructescences B Freshly cut branch with inflorescence and infructescences. Photos by A. C. Dietzsch, 5 July 2013.

Figure 4. Sommera cusucoana. A Tip of shoot with flower, developing fruits, and leaf pair emerging between pair of stipules B Flower at anthesis and developing fruit (appearing dark because in shadow). Photos by A. C. Dietzsch, 5 July 2013.