Dichaea fusca Valsko

Krahl, Dayse R. P., Chiron, Guy, Krahl, Amauri H., Da Silva, João Batista F. & Cantuária, Patrick De C., 2024, Notes on taxonomy, distribution and conservation of Dichaea species (Orchidaceae: Zygopetalinae) in Brazilian Amazon, Phytotaxa 638 (3), pp. 277-284 : 281-283

2. Dichaea fusca Valsko , Holanda & Krahl (in Valsko et al. 2014a: 134). ( Figure 3 ).

Type:— BRAZIL. Amazonas: Manaus: “Projeto Dinâmica Biológica de Fragmentos Florestais” (PDBFF), Fazenda Colosso, 2°24’21”S; 59°52’32”W, 15 February 2006, J.J. Valsko 107 (holotype: INPA!) .

Description:— Plant epiphytic, cespitose. Stem not swollen into a pseudobulb, 1.9–10.9 × 0.1 cm, elongated, compressed, usually unbranched, 10–40–leaved. Leaves 0.9–1.9 × 0.1–0.3 cm, narrowly elliptical, distichous, forming an angle of about 45° with the stem, conduplicate, apex acute. Inflorescence 0.7–1.2 cm long, lateral, 1-flowered, floral bract double; external bract 0.1–0.3 × 0.1–0.2 cm, ovate, apex apiculate; internal bract 0.2–0.3 × 0.05 cm, lanceolate, apex acute to acuminate. Flower brownish with a whitish lip, pedicellate; pedicel + ovary 0.2–0.5 cm long; dorsal sepal 0.3–0.5 × 0.15 cm, lanceolate, apex acute; lateral sepals 0.3–0.5 × 0.2 cm, lanceolate, apex acute; petals 0.2–0.4 × 0.1–0.2 cm, lanceolate, apex acute; lip 0.3–0.4 × 0.3–0.4 cm, trullate, trilobed; hypochile cuneate and slightly denticulate; epichile rounded and with an entire margin; lateral lobes triangular, asymmetrical, falcate and acute; apical lobe triangular, symmetrical and acute; column 0.1–0.3 cm long; pollinia 4. Fruit not seen.

Distribution and ecology:—From the material that we examined and referred to we can conclude that D. fusca is restricted to the Brazilian Amazon and occurs in two states. Hitherto it was known through the type material (holotype and paratypes) and some collections from the municipality of Manaus (Amazonas state) deposited in the INPA herbarium. However, from the specimens conserved in the herbarium MG, we could note its geographical expansion in the municipalities of Oriximiná and Terra Santa, both located in the far western part of the Pará state. In these localities D. fusca grows in dense rain-forests among a “terra-firme” vegetation in areas of “baixio” and “platô”. It occurs also among a vegetation of “campinarana”.

Conservation status:—The Area of Occupancy (AOO) is estimated at 36 km ². According to the criteria defined in IUCN Guidelines ( IUCN 2022), the threshold for Endangered category (EN) is met (criterion B). However, the species occurs in nine localities (corresponding to the category Vulnerable [VU] through the criterion Ba), five of them being within conservation units. Even so the total area of occupancy suffers a continuing decline (criterion Bb) due to deforestation, mostly out of the conservation units but non-only. The total number of mature individuals is estimated to 250 which is just the limit between the categories VU and EN (criterion D). Consequently the taxon may be treated as Vulnerable (VU category – criteria B2ab[II],D).

Taxonomic notes:— Dichaea fusca has been described by Valsko et al. (2014a) on the basis of material from the municipality of Manaus and has been erroneously and arbitrarily treated as a synonym of D. weigeltii (see Meneguzzo & Hall 2023), the type material of which is from Suriname, as shown in the drawing of the type deposited in the AMES herbarium (AMES00098867! – photography). Besides the presence of D. weigeltii in Brazil (Amazonas) is somewhat questionable. It is based on material deposited in the K herbarium (K000879277! – photography) which was treated as the species holotype according to Meneguzzo & Hall (2023). However, this material contradicts the information contained in the drawing of the type. In the illustration we see that the material is from Suriname and that Weigelt is the collector (C. Weigelt s.n.) and in the material indicated by Meneguzzo & Hall (2023) as holotype we see that the material is probably from Rio Negro ( Brazil, Amazonas) and that Spruce is the collector (R. Spruce 1719). Although Reichenbach (1859) does not formally indicate any type material for D. weigeltii in his protologue, we must trust the information contained in the type drawing because (a) it indicates C. Weigelt as the collector and (b) the taxon has been dedicated to him. Furthermore, Reichenbach (1859) confirms that D. weigeltii was collected by Weigelt in Suriname. He writes in his observation: “ Nova videtur species, quam tenemus ab Weigelt in Surinamo lectam et quae sub 1779 “Barra on trees in Forest. Jul. 1851. flowers pink” a Spruceo missa ”. (A new species, which we hold from Weigelt collected in Suriname and which was sent to Spruce under the number 1779 […]).

Moreover, the material deposited in K (K000879277!), as we could see, clearly corresponds to Dichaea tenuis Schweinfurth (1952: 510) mainly on the basis of the vegetative characters and because it is frequently common in the collection region indicated on the exsiccata when it was determined: "Probably a collection made by Spruce in Rio Negro, Brazil. ". This species is a taxon widely distributed in the Amazon basin ( Govaerts et al. 2023) and very common along the Rio Negro, mainly in the Manaus region (Amazonas) (personal observations). In D. tenuis the leaves are patent in relation to the stem, linear and relatively long in comparison to its size ( Schweinfurth 1952, 1961), features clearly observed in the material K000879277. Based on these characters present in both specimens AMES00098867 and K000879277, we could decide to treat D. weigeltii and D. tenuis as conspecific. However, the illustration of the lip of D. weigeltii in the former presents some clear differences compared to the illustration of the lip of D. tenuis (see Schweinfurth 1961), differences that prevent us to make such an affirmation.

Thus, we conclude that D. weigeltii is a taxon needing to be better elucidated and that its real determination should be better investigated before proposing any taxonomic conclusion as, for example, deciding that D. fusca is a synonym. Dichaea fusca is somewhat different from what is proposed in the illustration of D. weigeltii . The leaves of the former are narrowly elliptic (vs. linear in the latter) and arranged at a 45° angle (vs. patent) in relation to the stem. In the former the hypochile is cuneate and broader (vs. oblong and narrower) and the epichile is triangular apiculate concave (v s. anchor-shaped and rather acute) ( Reichenbach 1859, Valsko et al. 2014a). Consequently, D. fusca must, for now, be considered as a valid and independent species.

Additional material examined: — BRAZIL. Amazonas: Manaus: “Projeto Dinâmica Biológica de Fragmentos Florestais” (PDBFF), Fazenda Porto Alegre, 2°21’19”S; 59°57’31”W, 17 February 2012, J.J. Valsko 109 (INPA!) ; BR 174, Km 45 , Reserva Biológica de Campina , 2°35’29.9”S; 60°01’49.5”W, 20 December 2012, A.H. Krahl & D.R.P. Krahl 404 ( INPA!) ; Ramal Vale do Novo Amanhecer , 20 February 2016, A.H. Krahl & J.J. Valsko 547 ( INPA!) ; Ramal Castanheira , 24 February, 2019, A.H. Krahl 1112 ( INPA!) ; Reserva Florestal Adolpho Ducke , 03 May 2019, D.R.P. Krahl & A.H. Krahl 512 ( INPA!) ; idem, 12 June 2019, A.H. Krahl & D.R.P. Krahl 1254 ( INPA!) ; idem, 22 February 2020, D.R.P. Krahl & A.H. Krahl 639 ( INPA!) ; Ramal da Usina , 02 February 2022, A.H. Krahl & D.R.P. Krahl 1639 ( INPA!) ; Pará: Oriximiná: Porto Trombetas , Floresta Nacional de Saracá-Taquera , platô Saracá , 13 March 2018, J.B.F. da Silva 3569 ( MG!) ; Terra Santa: Abaocu , ilha do Rio Nhamundá , 14 March 2018, R. Sousa & J.B.F. da Silva 23 ( MG!) .

Figures

FIGURE 3. Dichaea fusca. A. Habit. B. Flower. C. External floral bract. D. Internal floral bract. E. Perianth. F. Lip. G–I. Column. J–K. Anther cap. L–M. Pollinarium. Photographs by A.H. Krahl.