Lacandonia brasiliana A.Melo & M.Alves, 2012

Melo, Aline & Alves, Marccus, 2012, The discovery of Lacandonia (Triuridaceae) in Brazil, Phytotaxa 40, pp. 21-25 : 22-24

Lacandonia brasiliana A.Melo & M.Alves , sp. nov., Figs. 1 A-B, 2 A–E

Type: — BRAZIL. Paraíba: Mamanguape , 06°43'' S, 35°05’W , Guaribas Biological Reserve , 25 September 2010, A . Melo, M. Alves, M.R.V. Barbosa, S.O. Santos, J.L. Viana, G. Gomes-Costa & E.C.O. Chagas 487 (fl., fr.) (holotype JPB, isotypes NY, UFP) .

Myco-heterotrophic, monoecious herbs, up to 9 cm tall, hyaline, glabrous; stem unbranched. Roots filiform. Leaves absent. Inflorescence racemose, terminal, bracteate, up to six flowered, or solitary flower; bracteoles 1.0–1.5 × 0.5–1.0 mm, ensiform to triangular, apex acute; flowers 2–3 × 2–3 mm, actinomorphic, bisexual; pedicel 1–3 mm long, tepals 4–6, persistent, 1–2 × 0.5–1.0 mm, isomorphic, deltoid, with a central vein prominent, caudate, 0.5–1.5 mm long; ovary> 35, papillose, apocarpic, surrounding the androecium, style up to 1 mm long., lateral; stamens 3–4, persistent, inserted at the edge of receptacle, anthers 0.2–0.5 mm, globoid. Fruits achenes, up to 1mm long.

Notes:—Previous to this study, Lacandonia was considered to be a monotypic genus, represented by L. schismatica , which is known only from the Lacandon region in Chiapas, Mexico ( Martínez & Ramos 1989, Ambrose et al. 2006). It was previously placed in a separate family, Lacandoniaceae , because it is the only angiosperm in which the ovaries surround the androecium. It also has an apocarpic ovary, three to four central stamens, and bilocular, transversely dehiscent anthers ( Martínez & Ramos 1989). Later, the species was placed in Triuridaceae (Maas-van de Kamer & Weustenfeld 1998, APG II 2003). The atypical position of the gynoecium and androecium is suggested by Mabberley (2008) as a possible case of homeotic mutation.

The genus was previously known only from Mexico and was considered endemic to that country ( Martínez & Ramos 1989, Ambrose et al. 2006). Our record of populations of a taxon belonging to the same genus in Brazil is therefore the first in South America. It is a remarkable case of disjunction between Mesoamerica and the Brazilian Coastal Forest. The Brazilian specimens, here described as the new species L. brasiliana , fit within the morphological characterization of L. schismatica , albeit at the lower range of number of ovaries and plant size as cited by Martínez & Ramos (1989) and Vergara-Silva et al. (2003). Lacandonia brasiliana differs from L. schimatica in having solitary flowers or inflorescences with up to six flowers, and more than 35 papillose ovaries. Molecular studies, comparing Mexican and Brazilian specimens could resolve the question if these geographically isolated populations should actually be treated as different species.

Lacandonia brasiliana was found in the extreme north of the Atlantic Forest in northeastern Brazil, in the state of Paraíba, about 20 km from the coast, a region with an average maximum annual temperature of 26ºC and rainfall of 1,700 mm /year. It grows in sandy soil in semideciduous forest with a canopy around 15 m high. The forest fragments in the study area are distinguished by the high diversity of trees. Neither selective wood cutting nor other kind of human disturbance was observed in the area. Lacandonia brasiliana was collected in moist, organic, and decomposing substrate and found fertile in August and September.

According to Martínez & Ramos (1989), L. schismatica blooms throughout the year in Mexico, but most numerously so in November and December. Lacandonia brasiliana blooms in August and September. They are distinguished from other species of Triuridaceae mainly by its bisexual flowers with apocarpic ovaries surrounding the androecium, and the hyaline stem. It occurs in sympatry with other myco-heterotrophic species such as Gymnosiphon divaricatus (Benth.) Benth. & Hook. f. ( Burmanniaceae ), Voyria caerulea Aubl. and V.tenella Hook. (Gentianaceae) .

Additional specimen (paratype):— BRAZIL. Paraíba: Mamanguape, Guaribas Biological Reserve , 17 August 1988, L. P. Félix & C. A. B. Miranda 3607 (fl., fr.) ( EAN!, JPB!).

Figures

FIGURE 1. a, b. Lacandonia brasiliana (Melo et al. 487) collected in the Guaribas Biological Reserve.