Vanilla dubia Hoehne ( Hoehne 1944: 126 )

Pansarin, Emerson R. & Miranda, Marcelo R., 2024, Clarifying the dubious identity of Vanilla dubia Hoehne (Orchidaceae) and its relatives, Plant Ecology and Evolution 157 (2), pp. 236-243 : 236-243

Vanilla dubia Hoehne ( Hoehne 1944: 126)

Figs 1 , 2 , 3 , 4 , Table 1

Type.

BRAZIL • s. loc.; s. d.; Schwacke 11107; holotype: RB [ RB 00542722 , accession n ° 37014] .

Description.

Nomadic vines, long scandent. Roots axillary, 1.6–2.1 mm diam., whitish to greenish brown, one per node. Stem climbing, sinuous, cylindrical, fleshy, slightly sulcate, glabrous dark green; internodes 55–130 × 3–6 mm. Leaves 5.5–22 × 2–4.8 cm, alternate, distichous, lanceolate to oblanceolate, rarely elliptic, asymmetric, coriaceous, glabrous, dark green, with prominent and parallelly arranged vascular bundles in transverse section, margin entire, apex acuminate, pseudopetiolate; pseudopetiole sulcate, up to 1.8 cm long. Inflorescence 3.7–7 cm long, axillary, racemose, with up to 20 flowers opening in succession; 1 flower opening each morning; bracts 3–5.2 mm long progressively smaller toward the apex, alternate, triangular to ovate, coriaceous, concave, patent, apex acute. Flowers resupinate, pedicellate, with an abscission layer between perianth and ovary; pedicel with ovary 3.5–3.9 × 0.3–0.35 cm, straight to incurved, dilated at the apex, subcylindrical in transverse section, white along the pedicel and green along the ovary. Sepals 6–6.2 × 1.1–1.3 cm, free, oblanceolate, fleshy, slightly concave, internally cream-coloured, externally greenish, apex obtuse, margin entire, reflexed at apex; dorsal sepal symmetric; lateral sepals asymmetric. Petals 5.8–6.1 × 0.8–1.2 cm, free, lanceolate to slightly spatulate, asymmetric, membranous, apex acute, slightly reflexed, internally cream-coloured, externally greenish, adaxial surface with a central and longitudinally arranged keel. Labellum 3 - lobed, 5.8–6.2 × 3–3.2 cm, unguiculate, tubular, fused to the column along the margins from the base, up to 3.6 cm long, white, yellowish in the distal portion, inner surface with longitudinal brownish stripes, with a central crest near the apex, and with a penicillate callus just below the anther; central crest ca 5 mm wide, with large yellow and tuberculate protrusions near the apex, on the midlobe; penicillate callus 4–4.5 × 3.5–3.8 mm, white; labellum margins fused from the base to ca 3 / 4 of the column length forming a tubular nectar chamber; nectar chamber 2.2–2.4 cm long; lateral lobes obliquely rounded, overlapping above the column, margins undulate to crenulate; apical lobe emarginated, reflexed, margin undulate to slightly crenulate. Column 4.5–4.7 × 0.3–0.35 cm, semi-cylindrical, slender, base attenuate, dilated to the apex, with white-hyaline hairs close to the stigma, apex with two lateral wings; anther 4.7–5 × 3.7–4.2 mm, rhomboid, white, versatile; rostellum 4.5–4.7 × 3.4–3.6 mm, trapezoidal, membranous, white. Fruits 5–7 × 1.2–1.5 cm, linear, incurved, subcylindrical in transverse section, fleshy, indehiscent, green when immature, black when mature. Seeds ovate, black.

Distribution and ecology.

Vanilla dubia occurs in primary forests of the Atlantic Rainforest in south-eastern Brazil (Fig. 2 ). It shows a nomadic vine habit, rooting on the forest litterfall and climbing on trees. The elevation is from 30 to 810 m a. s. l. Flowers open in morning hours. Each flower lasts ca 12 hours. The fruits are indehiscent, black, and ripen in nine months from pollination.

Phenology.

Vanilla dubia blooms from October to December. The fruits ripen between May and June.

Preliminary IUCN conservation assessment.

Endangered: EN B 2 ab (i, ii, iii). Vanilla dubia is an uncommon and rarely collected species currently known to grow in the Atlantic Forest areas of south-eastern Brazil. The populations found are composed of few sparse specimens. The extent of occurrence (EOO) is estimated to be 7,953.845 km 2, which falls within the limits for Vulnerable (VU) under subcriterion B 1, according to the IUCN red list categories and criteria and guidelines. The area of occupancy (AOO) is estimated to be 24 km 2 (cell width 2 km), which falls within the limits for Endangered (EN) under criterion B 2 (area of occupancy). Considering that the Atlantic Forest areas have been reduced to scattered fragments due to extensive human occupation, we project a continuing decline in (i) extent of occurrence, (ii) area of occupancy, and (iii) extent and / or quality of habitat of V. dubia . Based on these threats and on the fact that the species is distributed in less than five locations, V. dubia is assessed as Endangered (EN B 2 ab (i, ii, iii )).

Additional material examined.

BRAZIL – Espírito Santo • Santa Leopoldina, Rio das Farinhas ; 20 ° 6 ’ 7 ” S, 40 ° 36 ’ 58 ” W; 40 m; 16 Oct. 2003; A. P. Fontana 626; MBML • Moxafongo ; 20 ° 6 ’ 53 ” S, 40 ° 31 ’ 54 ” W; 150 m; 19 Nov. 2005; A. P. Fontana, C. Esgario, A. M. de Assis, K. F. O. Faria & V. Pagund 1797; MBML • Santa Teresa, Topo do Canaã ; 19 ° 55 ’ 5 ” S, 40 ° 35 ’ 58 ” W; 685 m; 4 Apr. 2004; R. R. Vervloet et al. 1841; MBML • Alto Santo Antônio ; 19 ° 53 ’ 14 ” S, 40 ° 34 ’ 32 ” W; 25 Feb. 2005; A. P. Fontana; et al. 1131; MBML • Estrada da Pedra da Onça ; 19 ° 53 ’ 29 ” S, 40 ° 49 ’ 8 ” W; 10 Sep. 1998; L. Kollmann, E. Bausen & W. Pizziolo 519; MBML . – São Paulo • Ubatuba, Praia Dura ; 23 ° 29 ’ 35 ” S, 45 ° 10 ’ 30 ” W; 30 m; E. R. Pansarin & M. R. Miranda 1574; LBMBP .

Notes.

Hoehne (1944) assumed that the holotype of Vanilla dubia was collected in Minas Gerais based on the fact that the Damasio Herbarium was located in Ouro Preto. However, to date, there is no evidence of the occurrence of this species in Minas Gerais. If the holotype of V. dubia (Schwacke 11107) was collected in Minas Gerais, it was most likely from the east of the State in areas of Atlantic Forest sensu stricto, on the borders with Espírito Santo State, where this species has been most commonly found. Hoehne (1944) also suggested that the holotype of V. dubia can be a mixture of elements from distinct Vanilla species. However, according to our data based on live plants plus herbarium material, there is no mixture of elements in the specimen Schwacke 11107. Considering that the description by Hoehne (1944) was based on a single collection, we conclude here that the Schwacke 11107 (RB) specimen is the holotype of V. dubia .

Morphological affinities.

Vanilla dubia is easily recognized by its coriaceous and dark-green leaves with prominent and parallelly-arranged vascular bundles in transverse section (Fig. 3 ), by its lateral inflorescence with small flowers whose sepals and petals are internally cream-coloured and externally greenish, by its white 3 - lobed labellum with yellow lobes and undulate-crenulate margins, and by its tuberculate appendages on the apical portion of the labellar crest (Fig. 4 ). These characteristics suggest a close relationship of V. dubia with V. dungsii and V. paulista , as all three species have a long-unguiculate labellum with a ventral penicillate callus and labellar protrusions on the midlobe. Vanilla dubia is more related to V. dungsii than to V. paulista . In fact, V. dubia and V. dungsii occur in Atlantic Forest areas, while V. paulista occurs in drier environments (i. e. semi-deciduous forests). Although V. dubia and V. dungsii occur in the Atlantic Forest, the habitat of V. dungsii differs from that of V. dubia . Vanilla dungsii occurs in high altitude areas of Rio de Janeiro, above 1000 m a. s. l., in the Dense Montane Ombrophilous Forest (Fig. 2 ). With regards to the vegetative characteristics, both V. dungsii and V. dubia have coriaceous and asymmetric leaves with prominent veins, while V. paulista show fleshy and more commonly symmetric leaf blades (Fig. 3 ). Although leaf size and thickness have been intriguing factors regarding the identity of V. dungsii , our data show that these characteristics overlap with those of V. dubia . The floral characteristics of V. dubia also suggest close affinity with V. dungsii . Both taxa have brown longitudinal bands over a white labellum and tuberculate appendages on the apex of the labellum. However, the labellar appendages of V. dungsii are much larger and fewer in number than in V. dubia . In V. paulista , the longitudinal bands are yellow and the labellar protrusions are white papillae arranged in 1–3 rows (Fig. 4 ).

Figures

Figure 1. Vanilla dubia Hoehne. A. Inflorescence. B. Leaf. Note the asymmetrical shape of the leaf blade and the acuminate apex. C. Flower in front view. D. Flower in lateral view. E. Flower in diagonal view. F. Dissected perianth. G. Detail of the adaxial surface of a petal showing the longitudinal keel. H. Detail of the apex of the labellum of a flower showing the brown longitudinal lines and the central crest with yellow projections. I. Detail of the labellum showing the penicillate callus and the central labellar crest. J. Labellum in dorsal view. K. Labellum in lateral view. L. Longitudinal section of the labellum. Note the penicillate callus (arrow), the anther (a), and the rostellum (arrowhead). M. Column in lateral view. N. Apex of the column: in abaxial view with an articulated and disarticulated anther (above), in lateral view with an articulated anther (mid), in lateral view with a disarticulated anther (bellow). O. Anther in dorsal view (left) and ventral view (right). P. Immature fruit. Based on E. R. Pansarin & M. R. Miranda 1574 (LBMBP). Photographs by Emerson Pansarin.

Figure 2. Map with records of occurrence of Vanilla dubia Hoehne and related species, Vanilla dungsii Pabst and Vanilla paulista Fraga & Pansarin. Records of occurrence of V. paulista and V. dungsii are based on the locality of type specimens. Map created with QGIS v. 32.2 (QGIS Development Team 2024).

Figure 3. A. Variation in the shape of leaf blades of Vanilla dubia Hoehne, based on E. R. Pansarin & M. R. Miranda 1574 (LBMBP). B. Leaf of V. paulista Fraga & Pansarin, based on E. R. Pansarin 727 (UEC). C. Comparative anatomy of the mid portion of leaf blades of V. dubia (above) and V. paulista (below). Photographs by Emerson Pansarin.

Figure 4. Comparative morphology of the flowers of Vanilla dubia Hoehne and related species. A. Vanilla dubia Hoehne (Ubatuba, São Paulo). B. Vanilla dungsii Pabst (Nova Friburgo, Rio de Janeiro). C. Vanilla paulista Fraga & Pansarin (Jundiaí, São Paulo). Details bellow the flowers (oval frames) show the types of labellar protrusions among the three Vanilla species. A. Based on E. R. Pansarin & M. R. Miranda 1574 (LBMBP). B. Based on a living specimen collected in Nova Friburgo, Rio de Janeiro. C. Based on E. R. Pansarin 727 (UEC). Photographs by Emerson Pansarin (A and C), and Jorge Gastin (B).