Cestrum darienense A.K.Monro, 2012

Monro, Alex K., 2012, Eight new species of Cestrum (Solanaceae) from Mesoamerica, PhytoKeys 8, pp. 49-82 : 57-59

Cestrum darienense A.K.Monro sp. nov. Fig. 4 A-D

Diagnosis.

Most similar to Cestrum morae Hunz. from which it can be distinguished by its thinner, more delicate stems, the lower number of secondary veins in the lamina, the ascendant and shorter inflorescences bearing flowers with shorter corolla tubes and longer corolla lobes.

Type.

Panama. Darién: Cerro Pirre, valley between between Pirre and next most southerly peak, sloping hillside, 07°40'N, 077°42'W (DMS), 1250-1300 m, J.P. Folsom, R. L. Hartman & R. L. Dressler 4415 (holotype: MO-2620728).

Description.

Shrub, occasionally lax, 1.0-2.5 m. Leaf-bearing stems grey-brown, the internodes 16-95 × 1.25-2.75 mm; young stems moderatley pubescent, the hairs 0.125-<0.25 mm, simple, weakly appressed, curved, glandular. Axillary buds 0.675-1.0 mm, red-brown, densely pubescent, not subtended by a minor leaf. Lamina 55-160 × 22-83 mm, length width ratio 1.86-3.0, broad rhombic-elliptic, rhombic-obovate, ovate-rhombic, obovate, rhombic, chartaceous, brown-green to brown; the upper surface glabrous, primary and secondary, primary to tertiary veins clearly visible to the naked eye, primary, primary and secondary raised; the lower surface sparsely pubescent, the hairs ca. 0.125 mm, simple, sessile to subsessile, glandular, weakly appressed, straight, orange-brown, primary to quarternary, primary to tertiary veins clearly visible to the naked eye, primary and secondary, primary to tertiary veins raised, the veinlets visible, unbranched, secondary veins 3-7 pairs, 30-45° to the midrib, straight, weakly curved; base subcordate, asymmetrical, obtuse, cordate-cuneate, cuneate; margin entire to irregularly entire; apex cuspidate, acuminate, subacuminate; petioles bottle-shaped, 3.5-8.0 × 1.375-2.0 mm, dark brown, moderatley pubescent, sparsely pubescent or glabrous, the hairs 0.125-0.25 mm. Inflorescences 2-13 per herbarium sheet, axillary, solitary in each axil, borne along the full length of leaf-bearing stem, 35-48 mm long, bearing 4-6 flowers in a panicle, the bracts forming a loose involucre around 1 or 2 clusters of flowers, each cluster bearing 3-5 flowers; peduncle 3.5-13.0 × 0.5-1.0 mm, dark brown to brown, moderatley pubescent or sparsely pubescent, the hairs 0.125-0.250 mm, glandular; bracts 3.5-10.0 × 2.0-5.5 mm, leaf -like; bracteoles 6-10 mm, ovate, obovate, rhombic, moderatley pubescent. Flowers subsessile, the pedicels <0.25 mm; calyx 2.75-3.25 × 1.25-1.75 mm, the outer surface glabrous, the lobes 5, 0.50-0.675 mm long, erect; corolla white, 22-30 mm long, the tube 18.5-24.0 mm long, 1.5-2.0 mm in diameter at the mouth, 0.675-1.0 mm at the base, glabrous, the lobes 5, 7-9 mm long; stamens 5, the filaments 15-22 mm, equal, adnate for 13.5-19.5 mm, glabrous, with a lobe-like appendage present at insertion point, the appendage pubescent, the anthers 0.75 × 0.675 mm; style 17.0-19.5 mm, the stigma 0.675 × 0.75 mm. Infructescences and fruit not seen.

Etymology.

This species is named after the Darien province, locality of the type and paratype collections.

Distribution.

Cestrum darienense is known from two localities in Cerro Pirre and whilst none of the collection labels indicate a forest type, altitude information would suggest that this would be cloud forest. Cerro Pirre covers an area of ca. 50 × 25 km. Using collection label data and Google Earth (accesssed June 7, 2011; images from 2003) the Extent of Occurrence for this species is calculated to be ca. 280 km2.

Discussion.

Of the three collections of Cestrum darienense seen, none had been previously determined to species prior to this study. A comparison of the holotype and paratype material with type specimens from the herbaria listed in the Materials and methods section recovered Cestrum darienense as most similar to Cestrum gilliae A.K. Monro and Cestrum morae Hunz. Together with Cestrum langeanum D’Arcy, Cestrum darienense , Cestrum gilliae and Cestrum morae form a coherent morphological and geographical grouping within the genus of species from western Panama and the Chocó in Colombia and Ecuador characterised by broad, nearly three-veined leaves and determinate inflorescences. Cestrum darienense can be distinguished from Cestrum morae and Cestrum gilliae on the basis of stem, leaf, inflorescence and flower morphology as summarised in Tables 5 & 6 . The Cerro Pirre mountain range has been noted as a locality for many endemic plant and animal species; this has been attributed to it being a moist forest refugium during dry periods of the Pleistocene (Haffer 1967).

Conservation status.

Using IUCN criteria ( IUCN 2001), Cestrum darienense is considered to be Near Threatened. The Extent of Occurrence is calculated to be ca. 280 km2 (Criteria B1 <5,000km2) and there are only two known localities (Criteria B1a ≤5, Endangered). No decline in geographic range or fragmentation of the habitat has been observed, however, and Cerro Pirre is located within the Darién Biosphere Reserve, a UNESCO World Heritage Property. The Darién is vulnerable to factors which may result in future deforestation, e.g. economic development associated with the resolution of the armed conflict in neighbouring Colombia and or an end to narco-trafficking. Any associated decline in geographic range or fragmentation would result in this species being assessed as Endangered.

Paratypes.

PANAMA. Darién: Serranía de Pirre, trail ca. 1 mi SSW of Cerro Pirre summit, 07°56'N, 077°42'W (DMS), 1200 m, 15 Jul 1977, R. L. Hartman, J. P. Folsom & R. L. Dressler 4655 (MO); Cerro Pirre, along stream between Pirre and next southern peak, 07°40'N, 077°42'W (DMS), 10-20 Jul 1977, J. P. Folsom 4383 (MO).

Figures

Figure 4. Cestrum darienense A. K. Monro A Flowering stem B Style C Longitudinal section through the corolla showing stamen arrangement D Flower. Drawn from J. P. Folsom, R. L. Hartman & R. L. Dressler 4415 (MO).