Catasetum × humaitaense Krahl, D.R.P.Krahl, Schmal & Cantuária, 2025

Krahl, Dayse R. P., de Oliveira, Miguel S., Schmal, Philippe, da Silva, João B. F., Chiron, Guy, Krahl, Amauri H. & Cantuária, Patrick de C., 2025, Catasetum × humaitaense (Orchidaceae: Catasetinae), a new nothospecies from the Brazilian Amazon, Biota Colombiana 26, pp. 1-14 : 5

Catasetum × humaitaense Krahl, D.R.P.Krahl, Schmal & Cantuária nothosp. nov.

Diagnosis: Catasetum × humaitaense hybrida naturalis inter C. boyi et C. ivanae cum characteribus intermediis est. inflorescentia arcuatis et descendentibus, flores pallidi sparsim brunneomaculati, sepala oblongo-elliptica, petala elliptica, labelum ovatum subtrilobatum margine irregulariter denticulum cum duobus callis in loborum lateralium basi.

Type. BRAZIL. Amazonas , Humaitá , Madeira River, Carapanatuba Lake, igapó forest, 6°46´22.11´´ S-62 °42´36.51´´W, 33 m a.s.l., 23 march 2023, R. R. P . Nascimento ex A. H . Krahl & P . Schmal 1690 ♂ (holotype: HUAM012581 !) .

Description. Epiphytic caespitose plant. Roots fasciculate, filiform, whitish, ca. 0.4-0.5 cm diam. Rhizome inconspicuous. Stem swollen into a pseudobulb, 6.4-7.9 × 1.9-2.5 cm, fusiform, covered by leaf sheaths, multi-leaved, greenish. Leaves 7.1- 16.6 × 2.5-3.9 cm, oblanceolate, plicate, abaxially clearly 5-6-nerved, entire and slightly undulate margin, acute apex, green. Staminate inflorescence 8.2-9.9 cm long, lateral, racemose, arched descending, 5-6-flowered; peduncle 0.2-0.3 cm long, cylindrical, greenish becoming purplish towards apex; bracts at the peduncle base 0.6-0.7 cm long, amplective, entire margin, acute apex, greenish; floral bract 0.8-0.9 × 0.3-0.4 cm, lanceolate, concave, symmetrical, entire margin, acute apex, greenish. Staminate flowers light green with brown-spotted, spaced by about ca. 1 cm, resupinate, pedicelled; pedicel 1.6-1.8 cm long, cylindrical, sinuous, brownish; sepals 2.5-2.8 × 0.9-1.1 cm, ellipticlanceolate, involute, symmetrical, entire margin, acute apex; petals 2.2-2.4 × 0.8-0.9 cm, ellipticlanceolate, slightly revolute at base, symmetrical, entire margin, acute apex; lip 1.2-1.4 × 1.0- 1.1 cm, ovate, subtrilobed, tough and fleshy, with an ovoid bottom ca. 0.5-0.6 cm deep and two discreet calli at the base of the lateral lobes; calli 0.1-0.2 × 0.1-0.2 cm, transversely laminar, obtuse; lateral lobes 0.5-0.6 × 0.7-0.8 cm, semi-ovate, irregularly denticulated margin; apical lobe 0.5-0.6 × 0.7-0.8 cm, deltoid, discreetly denticulated margin, obtuse and revolute apex; column 1.8-2.0 cm long, oblanceoloid, thick, contracted at base, rostrate apex, greenish with brown-spotted; antennae 0.6-0.7 cm long, filiform, symmetrical, convergent, brownish; anther cap 0.6- 0.7 × 0.3-0.4 cm, subtriangular, purplish brown, rostrate apex; viscidium ca. 0.1 × 0.1 cm, rounded, sticky; stipe ca. 0.3 × 0.1 cm, blade-shaped, rolled, yellowish; pollinia 2, 0.1-0.2 × 0.1 cm, oblong, hard, sulcate, compressed, yellowish. Pistillate and staminate + pistillate inflorescences not seen. Fruit not seen.

Etymology. The specific epithet refers to the name of the municipality of Humaitá (Amazonas, Brazil), where the new nothospecies was found.

Distribution, habitat and ecology. The new nothospecies flowered in cultivation during March, a period that corresponds to the rainy season in the Brazilian Amazon ( Braga, 1977). It is currently known only from the type locality: Lake Carapanatuba, situated in the municipality of Humaitá, Amazonas state, Brazil ( Figure 2 ). The species was observed growing epiphytically on thin tree branches in igapó forest, a typical Amazonian environment subject to seasonal flooding. Field observations indicate that C. × humaitaense grows in sympatry with one of its putative parental species, C. ivaneae , and both share the same locality (see Petini-Benelli,2016b; vouchers: CNMT6768!, CNMT6769! and RB01017642!). This type of flooded habitat is also known to support other congeneric nothospecies, such as C. × sheyllae Krahl , Cantuária & J.B.F.Silva, recently described from the state of Pará ( Cantuária et al., 2021).

Figures

Figure 2. Map with the type locality (red dot) of Catasetum × humaitaense nothosp. nov. in the state of Amazonas (Brazilian Amazon).