Dialium hexaestaminatum

Junior, Marcus José De Azevedo Falcão, Pinto, Rafael Barbosa & Mansano, Vidal De Freitas, 2016, A Taxonomic Revision of the genus Dialium (Leguminosae: Dialiinae) in the Netotropics, Phytotaxa 283 (2), pp. 123-142 : 131-132

2. Dialium hexaestaminatum M. J. Falcão & Mansano. sp. nov. Figure 3 .

Diagnosis: Dialium hexaestaminatum differs from other neotropical species of Dialium by the presence of (4–)6(–7) stamens. The most common number of stamens is 6. Dialium guianense , Dialium congestum and Dialium rondoniense only have 2 stamens.

Type:— COLOMBIA. Antioquia: Município de San Luis Quebrada “La Cristalina”, 6° N 74° 45’ W, 30 October 1987 Juan Guillermo Ramirez y Dayron Cárdenas López 1989 (Holotype: MO! Isotypes: COL!).

Trees, up to 30m tall; trunk cylindrical, up to 45cm in diam.; branches glabrous. Stipules lanceolate, 1.0– 3.3mm, glabrous, persistent. Leaves with 5–8(–9) leaflets, alternate; petioles cylindrical, 0.9–1.8 × 0.1–0.2cm; rachis cylindrical, 3.4–9.5 × 1–2mm, glabrous or sparsely pubescent; petiolules cylindrical, 0.2–0.5 × 1–2mm, glabrous or sparsely pubescent; leaflet blades chartaceous, elliptic to oval, 1.7–10 × 1.1–4.4cm, glabrous; base cuneate to slightly obtuse, apex acuminate to acute; acumen rounded apically, 0.3–2.9cm; venation slightly prominent adaxially, quite prominent abaxially. Inflorescences brownish, apical or axillary, with several tens to hundreds of flowers, terminal branches with 1–3 flowers arranged in a lax form; main axes of inflorescence cylindrical, 7–16 × 0.1– 0.2cm, pubescent; pedicels cylindrical, 3–4 × 1mm, pubescent. Bracteoles 2, 1.7 × 0.6mm, inserted at the base of the flower bud, pubescent, caducous. Calyx brown, zygomorphic, slightly pubescent internally, densely pubescent externally, segments five, unequal, 1.9–3 × 1–1.5mm. Petals absent. Receptacle expanded, pubescent, 1.5–2.6mm wide. Androecium actinomorphic to zygomorphic; stamens (4–)6(–7); filaments cylindrical, about 1mm long in the bud, glabrous; anthers yellow, elliptical, 0.7–1.2 × 0.5–1mm, glabrous, apex cuspidate. Ovary elliptical, 0.8–2 × 0.6–1.5mm, brown, pubescent, sessile; ovary with 1–2 ovules; style apical, cylindrical, 0.5mm in the bud, slightly pubescent; stigma papillate. Fruits and seeds not observed.

Distribution and habitat:— Dialium hexaestaminatum occurs on the northern edge of the Andes in northern Colombia and extreme northwestern Venezuela. It is usually associated with relatively high elevations (to 770 m). The distribution of D. hexaestaminatum overlaps with D. guianense in the northern part of its distribution in Colombia ( Figure 4 ). There are numerous collections from northern Colombia and northwestern Venezuela in the area of occurrence of D. hexaestaminatum that were not clearly identified, which is because they are sterile or have only fruits and it is only possible to identify these species by the number of stamens. In rare cases, virtual herbarium images of specimens with buds and flowers were not identified because it was impossible to determined the number of stamens. These specimens were excluded from the treatment and will be studied more carefully later in order to determine their identity. A complete list of these 56 specimens is presented in the Appendix 2. Genetic analyses are being conducted that may clarify these issues.

Phenology:— Flowers in April, August, September, October and November. Fruiting time unknown.

Etymology:—The specific epithet refers to the large number of stamens (usually 6) found in all individuals of this species.

Comments:— Apparently the geographic barriers between populations caused by the occurrence in different elevations might have been an important factor in the speciation of this taxon. Most individuals of D. hexaestaminatum are associated with relatively high elevations in mountain regions on the northern edge of the Andes. Only three individuals have been recorded below 350m elevation (100m, 160m and 200m), the remaining occur between 350m to 770m.

Other specimens analyzed (paratypes):— COLOMBIA, Antioquia, Municipio de San Luis, Quebrada “La Cristalina”, 6° N 74° 45’ W, 29 September 1987, J. G. Ramirez y D. Cárdenas L. 1776 ( MO!, COL!) ; Antioquia, Municipio de San Luis, Corregimiento “El Prodigio”, Camino de “El Prodigio” a La Hacienda “El Tigre”, 6° 06’ N 74° 45’ W, 24 September 1990, D. Cardenas L., J. G. Ramirez & L. A. Osorno 2960 ( MO!) ; Ayapel, Carretera entre La Escobilla y Hacienda Canime, vegetacion dispera, zona aberta, 3 April 1990, O. Marulanda 2041 ( MO!) ; Córdoba, Tierralta, Vereda La Oscurana, Zona amortiguadora del P. N. N. Paramillo , Cerro Murrucucú , 8° 00’ 36’’ N 76° 06’ 11’’, 28 September 2008, J. D. Garcia G., A. Avella M., P. Hernández. C. Estupiñan, D. Jimenez, H. Mendoza y M. L. Berdugo 655 ( COL!). Antioquia, Rio Pocuné-Zaragoza , 9 October 1967, Celis, J. 76 ( COL!). Bolívar, Ayapel, Palotal, 15 May 1949, R. Romero-Castañeda 1665 ( COL!) ; Antioquia, Tarazá, Corregimiento El 12, 210 kms, 7° 30’ N 75° 20’ W, 9 November 1987, R. Callejas, F. J. Roldán, A. L. Arbeláez, D. L. Echeverry 5490 ( NY!) ; Antioquia, Amalfi, Mina La Vetilla , margen derecha quebrada Vetillita , 74° 55’ W 7° 4’ N, 13 October 1991, D. Tuberquia & G. Gómez 18 ( NY!, MO!, COL!) ; Santander, 30 kms, al noroeste del caseiro de La Gómez. 8 October 1960, R. Romero Castañeda 8442 ( NY!) ; Santander, Región del Carare, Colonización Cimitarra. 28 August 1954, F. B. Lamb 178 ( COL!). Santander, 12 leguas al SE de Barranca bermeja, a 5 kms de la margen derecha del río Opón. 21 September 1954, R. Romero Castañeda 4878 ( COL!). VENEZUELA, Zulia, Sierra de Perijá , Faldas inferiores, Selva Macrotérmica, siempre verde, vecindad de La Quebrada da Koshida , al sur de La Misión de Los Angeles , 31 August 1967, J. A. Steyermark 99958 ( MO!, NY!) ; Zulia, Perijá, carretera Machiques-La fría, unos 10 kms, al norte del río Lora , 11 October 1979, G. S. Bunting, F. Arboleda L. 8100 ( NY!) .

Figures

FIGURE 3. Dialium hexaestaminatum. A. Flowering branch; B. Detail of the inflorescence; C. Longitudinal section of the ovary; D. Dorsal view of the stamen; E. Front view of the stamen; F. Flower at anthesis. A, B, C, D, E and F from J.G. Ramirez 1989. Drawn by Marcus J. A. Falcão.

FIGURE 4. Physical map of northern Colombia and western Venezuela showing the location of the collections analyzed of the species in the region (Source: ArcGIS with editions).