Dialium guianense (Aubl.) Sandwith (1939:184)

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 : 126-129

1. Dialium guianense (Aubl.) Sandwith (1939:184) . Figure 1 .

Basionym: Arouna guianensis Aublet (1775:16) . Lectotype: French Guiana. 1762-1764, Aublet s/n. P00680458 (MNHM!). Designated by Lanjouw & Uittien (1940).

≡ Arouna divaricata Willdenow (1797:156) . Basionym: Dialium divaricatum (Willd.) Vahl (1805:303) . Type. French Guiana. No date. Aublet. s/n. LINN-HS69-1 (LINN!).

= Dialium acuminatum Spruce ex Bentham (1870:180) . Dialium acuminatum S pruce ex L. Williams (1936:201). Type. Brazil. January 1852 to October 1853. Spruce 2688 (K!).

= Dialium floribundum Bentham (1870:180) . Type. Brazil, Pará, Santarém. July 1850, Spruce 972 (K!).

Trees, up to 50m tall; trunk cylindrical, up to 90cm in diam.; buttresses sometimes present, up to 2m tall; bark rich in lenticels, smooth to rough to slightly fissured, brown, gray or red; heartwood brown; sapwood cream yellow; exudate red or pink, translucent, sticky; branches cylindrical, glabrous. Stipules lanceolate, 1–4 mm long, glabrous, persistent. Leaves with (3–)5–7(–13) leaflets, leaflets often alternate; petioles cylindrical, 0.9–2.2cm × 1–3mm; rachis cylindrical, 2.9–12.9 × 1–3mm, glabrous; petiolules cylindrical, 1.8–6 × 1–3mm, glabrous or with a slight pubescence imperceptible to the bare eye; blades of the leaflets chartaceous, lanceolate to elliptic, 1.6–10(–14) × 1.1–5(–7.5)cm; glabrous or with sparse pubescence imperceptible to the touch and invisible to the bare eye; base cuneate to obtuse, apex acuminate to acute; venation slightly prominent adaxially, quite prominent abaxially; acumen rounded apically, 0.2–2.1 cm. Inflorescences brownish, apical or axillary, straight or curved, with several tens to hundreds of flowers, terminal branches with 1–3 flowers arranged in a lax form; main axes of the inflorescence cylindrical, 8.5–24cm × 1–4mm, pubescent; pedicels cylindrical, 1.4–7.8 × 1mm, pubescent. Bracteoles 2, 1.5 × 0.5mm, inserted at the base of the flower bud, pubescent, caducous. Calyx brown, green-yellow or green, zygomorphic, slightly pubescent internally, densely pubescent externally, segments five, unequal, 1.5–3.2 × 0.8–2mm. Petals absent. Receptacle expanded, pubescent, 1–3mm wide. Androecium zygomorphic; stamens 2; filaments cylindrical, 0.3–2mm long in the bud, glabrous to slightly pubescent; anthers yellow, generally elliptical, 0.8–2 × 0.4–1mm, slightly pubescent to glabrous, apex cuspidate to rounded. Ovary elliptical, 1.1–2.6 × 0.8–2.1mm, purple, pubescent, sessile to stipitate, stipe 0–0.5mm (this varying in flowers of the same individual); ovary with 1–2 ovules; style apical, cylindrical, 0.3– 4mm in the bud, slightly pubescent; stigma papillate, white. Fruit a camara, spherical to ellipsoid, sometimes laterally flattened, 1.5–2.9 × 1–2.3 × 0.6–1.4cm, purple to brown, smooth, glabrous or with a slight pubescence imperceptible to the bare eye. Seeds 1–2 per fruit, ellipsoid to spherical to irregular, 6–10 × 5–9mm, black to brown; endocarp covering the entire seed, 1.3–2.3 × 1–1.7cm.

Distribution and habitat:— Dialium guianense occurs in forests generally below 300m elevation (usually below 100m) and is generally associated with wetlands. It occurs in Mexico, Guatemala, Belize, Honduras, Nicaragua, Costa Rica, Panama, Colombia, Ecuador, Peru, Bolivia, Venezuela, Guyana, Suriname, French Guiana and Brazil. In Brazil it occurs in Amazonian rain forest and the Atlantic Forest, as well in transition areas between Amazonia and the Cerrado ( Figure 2 ).

Phenology:— Flowers and fruits throughout the year.

Comments:— In the original illustration by Aublet (1775), there are stipels visible at the bases of the leaflets. However, these structures have not been observed in any herbarium specimen (including Aublet’s collections) or living individual in situ. All four neotropical species of Dialium only have stipules at the base of the leaves.

The bracteoles are dehiscent and were only observed in young inflorescences of a few individuals of Dialium guianense and Dialium hexaestaminatum . The fact that bracteoles were not observed in the other two new species is probably due to the small number of samples analyzed (which did not have young inflorescences) and the loss of these organs during the process of herborization and senescence.

Bentham (1870) described Dialium divaricatum (synonym of D. guianense ) and cited the presence of 2 stamens,

or very rarely three. However, in all specimens examined in this study we found two stamens per flower, with the notable exception of individuals with 4 to 7 stamens from Colombia and Venezuela, which are described here as the new species D. hexaestaminatum .

We did not find any significant morphological differentiation between specimens of D. guianense from both sides of the disjunction in central Brazil. However, northeast and east of the disjunction there is a higher frequency of individuals with seven leaflets, which are generally smaller, while in the Amazonian specimens there is a higher frequency of individuals with five leaflets, which are generally larger.

All binomials mentioned in the synonym list were analyzed and no distinctive characteristics were observed in any of them; therefore, Arouna guianensis , A. divaricata and Dialium divaricatum are synonyms of Dialium guianense .

Although the name Dialium acuminatum is here cited as a synonym for D. guianense , there are three sources for this name:

(

1) Dialium acuminatum De Wildeman (1907: 139) —An African species unrelated to D. guianense . This is an example of a posterior homonym. This name is therefore illegitimate and its true identity should be verified based on a revision of the paleotropical species of Dialium (Falcão et al. in prep.).

(2) Dialium acuminatum Spruce ex Bentham (1870: 178) —This taxon was described based on two collections from the region of the Uaupés River (Vaupés), in the Brazilian Amazon, made by R. Spruce in 1853 (Spruce 2688 deposited at K with duplicates at MNHM, NY and JACQ; and Spruce 5167 deposited at RB), which are both determined on the label by Spruce as Dialium acuminatum . In one of these plants there is a small note, apparently written by Spruce, that appears to be a brief “description” of the species. Despite the difficulty reading his handwriting, it seems to refer to the presence of “globular” inflorescences. However, the specimens have the same inflorescences of those found in D. guianense (terminal lax thyrses), excluding two duplicates of Spruce 2688 that appear to have two different inflorescences in the same plant, the typical inflorescence of D. guianense and an inflorescence isolated from the vegetative parts that is much smaller with a globose shape. This is probably why Bentham separated these plants from the typical D. guianense . Nevertheless, this character does not seem to justify the recognition of a new species because there is variation among duplicates of the collections examined that may only be the result of poorly developed inflorescences. Additional collections from the region with these different types of inflorescences might shed more light regarding the existence of this taxon. Besides inflorescence type, it was also observed that these specimens possess inflorescences that are slightly pendulous distally, which is unusual among samples of typical D. guianense . However, the plasticity of this character remains unclear and the apparent pendulous inflorescences might have been caused by the collecting and pressing procedures. For now, we do not consider this feature a relevant taxonomic difference.

If the epithet “acuminatum ” refers to the apex of the leaflets, there is no difference between them and those of the typical D. guianense . There is great plasticity in leaflet shape, including variations in the base and apex, for example, the apex is often acuminate (including those of Spruce collections) and often acute in several collections made throughout the Neotropics.

A molecular study of several specimens with different inflorescences, including Spruce 5167, is underway. Results from these new phylogenies will help determine whether these leaf and inflorescence characters are synapomorphies, and will test the existence of a separate taxon.

(3) Dialium acuminatum Spruce ex Williams (1936: 200) —A tentative description of these plants collected by Spruce was made by L. Williams. The author did not mention the numbers of collections or any of the above morphological differences, indicating only the name of Spruce and limiting the description to dendrological features. This is not a validly published name. The material used by Williams (1936: 200) is the same used in the description of D. acuminatum Spruce ex Benth.

Dialium floribundum Bentham (1870: 178) was described based on collections from the state of Pará, in Brazil (R. Spruce s/n. K000835154; R. Spruce s/n P03100211; R. Spruce 972 in K, with duplicate in M). Bentham (1870) indicated that the species occurs in Pará and Bahia and mentioned the collection Spruce 972, as well as two other collections that we could not find (Hoffmannsegg s/n and Blanchet 1371). These collections do not present features that distinguish them from those usually identified as D. guianense . Therefore, Dialium floribundum is kept as a synonym of Dialium guianense .

Dialium guianense Steudel (1840: 497) is the result of a mistake made by Steudel (1840) due to the similarity between the names D. guianense and D. guineense (an African species). Therefore, Dialium guianense Steud. is not a new combination by Steudel, but rather a misspelling of Dialium guineense Willdenow (1796: 30) .

Selected specimens:— (29/686) (for complete list see Appendix 1). MEXICO, Ococingo, 3 km al NW del Rio Chixoy , 1 September 1985, E. Martinez 13661 ( MO!) ; BELIZE, Toledo, Rio Grande , 12 September 1944, P. H. Gentle 48211 ( MO!) ; GUATEMALA, Izabal, Puerto Barrios towards Guatemala City, on road to Piteros, 88° 32’ W 15° 40’ N, 22 March 1988, N. T. Marshall , J. J. Castillo M., E. W. Marshall 436 ( MO!) ; HONDURAS, Al norte de Krautara, Rio Patuca , Gracias a Dios, 84° 52’ W 15° 03’ N, 20 March 1995, P. R. House 2321 ( MO!) ; NICARAGUA, Jinotega, Cua Bocay , reserva de Bosawas, comunidade de Walakitan, 14° 29’ N 85° 05’ W, 28 September 2005, I. Coronado G., M. Barrios, G. Pérez 2147 ( MO!) ; COSTA RICA, Puntarenas, reserva indígena Guaymi, ca. 2 km al oeste de donde Rio Pavón se junta com Rio Rincón , 8° 37’ 00’’ N 83° 31’ 30’’ W, 13 August 1991, R. Aguilar 277 ( MO!, CR) ; PANAMA, San Blas, Cangandi, 9° 24’ N 79° 24’ W, 27 March 1986, G. de Nevers , H. Herrera, S. Charnely 7569 ( MO!) ; COLOMBIA, Chocó, Quibdó, Guaybel , Rio Hugón , 14 October 1985, L. Garcia , N. Selcedo , R. Palacios, L. Mena, A. Legarejo 80 ( MO!) ; VENEZUELA, Amazonas, Autana, Confluencia dos rios Sipapo e Cuao , 4° 54’ N 67° 34’ W, 21 September 1996, A. Castillo 3963 ( MO!) ; GUYANA, Potaro-Siparuni, Iwokrama, 4° 43’ N 59° 01’ W, 30 November 1994, Mutchnick P. 442 ( MO!, U) ; SURINAME, Lucie Rivier, 3° 20’ N 56° 49’ W, 4 September 1964, H. S. Irwin , G. T. Prance, T. R. Sodestrom, N. Holmgren 55368 ( NY!) ; FRENCH GUIANA, Rives de la riviere Camopi, afluente do Oyapock , 5 December 1967, Oldeman 2550 ( L, NY!, MNHM!) ; ECUADOR, Napo, Jatun Sacha, 01° 04’ S 77° 37’ W, 6–14 October 1988, W. Palacios 3142 ( NY!, MO!) ; PERU, Loreto, Maynas, Iquitos, Quistococha , 03° 48’ S 73° 25’ W, 28 April 1989, R. Vásquez e N. Jaramillo 12075 ( MO!) ; BOLIVIA, Pando, Manuripi, 35 km ao norte de Puerto América, 11° 44’ S 67° 59’ W, 1 May 1994, A. Jardim 619 ( NY!, MO!) ; BRAZIL, Acre, Bujarí, Riozinho do Andirá, 09° 43’ S 68° 07’ W, 28 December 2009, Medeiros H. 316 ( RB!) ; Amazonas, Presidente Figueiredo, Cachoeira do Boto , 21 September 2007, Carvalho Sobrinho J. G. de 1634 ( INPA!, RB!) ; Roraima, Caracaraí, 0° 41’ 46’’ S 62° 27’ 04’’ W, 27 October 2008, Junqueira A. B. 884 ( INPA!, RB!) ; Rondônia, Porto Velho, Santo Antônio , 09° 16’ 41’’ S 64° 29’ 28’’ W, 2 October 2012, G. P. Silva 16063 ( RB!, CEN) ; Mato Grosso, Aripuanã, km 238 da BR 174 , Núcleo Juina , 16 January 1979, M. G. Silva, A. Pinheiro 4284 ( RB!) ; Pará, Altamira, Juruá , 27 November 1986, S. A. M. Souza , O. C. Nascimento, M. R. dos Santos, W. Nascimento 553 ( RB!) ; Tocantins, Bacia do baixo rio Araguaia, Assentamento Vitória Régia , W0749760 / N9257280 , 29 June 2000, C. M. Vieira, F. Bonatto 1475 ( RB!, RFA) ; Maranhão, Alzilândia, Rio Pindaré, 3° 45’ S 46° 05’ W, 11 December 1978, J. Jangoux , R. P. Babía 340 ( RB!, INPA!) ; Pernambuco, Recife, Curado, Mata do comando militar do Nordeste , 8° 04’ 16’ S 34 ° 57’ 54’’ W, 28 January 1996, A. C. B. Lins e Silva , M. C. G. Tavares 150 ( RB!) ; Alagoas, Murici, Estação ecológica Murici , Estrada para as torres, 9° 14’ 28’’ S 35° 46’ 45’’ W, 31 July 2008, H. C. de Lima, F. L. R. Filardi, R. D. Ribeiro, A. G. da Silva 6987 ( RB!) ; Sergipe, Santo Amaro das Botas, 29 January 1992, C. Ferney , J. C. Gomes 3009 ( RB!) ; Bahia, Conde, Fazenda do Bu , 12° 2’ 24’’ S 37° 42’ 38’’ W, 25 April 1999, H. P Bautista, T. Jost 1787 ( RB!) ; Espírito Santo, Linhares, Reserva da CVRD, Estrada da Gávea , 19 September 1987, H. C. de Lima, M. P. M. de Lima 3130 ( RB!) ; Minas Gerais, Parque do Rio Doce , 42° 48’ S 19° 46’ W, 3 April 1981, F. C. F. da Silva 31 ( RB!) .

Figures

FIGURE 1. Dialium guianense. A. Flowering branch; B. Branch bearing fruits; C. Detail of the inflorescence; D. Flower at anthesis; E. Longitudinal section of the ovary; F. Sepal; G. Gynoecium; H. Stamen. A, C, D, E, F and G from A.C.B. Lins-e-Silva 150; B from T.M.C. Silva 27. Drawn by Marcus J. A. Falcão.

FIGURE 2. Physical map showing the location of the collections analyzed of all of the species (Source:ArcGIS with editions).