Vanilla schwackeana Hoehne

Pansarin, Emerson R., 2024, Rediscovery and revalidation of the Brazilian endemic Vanilla schwackeana Hoehne (Orchidaceae): its distribution and phylogenetic position, Plant Ecology and Evolution 157 (1), pp. 32-41 : 32

Vanilla schwackeana Hoehne

Figs 1 , 2

Type.

BRAZIL - Minas Gerais • s.loc.; s.d.; Schwacke 11106; holotype: RB [RB00542725, accession n° 37015] .

Description.

Nomadic vines, up to 8 m in length. Roots axillary, 1.8-2.2 mm diam., whitish to brownish, one per node. Stem climbing, sinuous, cylindrical, glabrous, fleshy, and green; internodes 42-80 × 3-4 mm. Leaves 5.5-11 × 3-5.5 cm, alternate, distichous, elliptic to obelliptic, symmetric to asymmetric, slightly fleshy, glabrous, green, pseudopetiolate, margin entire, base attenuate, apex acuminate; pseudopetiole 5.5-8 mm. Inflorescence 3.5-6 cm long, apical or axillary, racemose, with up to 10 flowers opening in succession; 1-2 flowers opening each morning; bracts 4-8.5 × 3.5-7 mm, progressively smaller toward the apex, alternate, triangular to ovate, coriaceous, concave, patent. Flowers resupinate, pedicellate, abscission layer between perianth and ovary present; pedicel with ovary 3-3.5 × 0.35-0.42 cm, green, straight to incurved, dilated at the apex, subcylindrical in transverse section. Sepals 4.2-4.6 × 0.8-1.1 cm, free, oblanceolate, fleshy, slightly concave, pale green, margin entire, slightly incurved, apex acute to obtuse; dorsal sepal symmetric; lateral sepals asymmetric. Petals 4-4.4 × 0.7-0.9 cm, free, slightly spatulate, asymmetric, membranous, pale green, apex acute, adaxial surface with a central and longitudinally disposed keel. Labellum 1-lobed to slightly 3-lobed, 4.2-4.7 × 2.5-2.7 cm, yellowish, white in distal portion, inner surface with longitudinal yellow stripes, with a central crest near the apex, and with a penicillate callus just below the anther; central crest ca 4 mm wide, with yellow protrusions arranged in 3-5 longitudinal lines near the apex; penicillate callus 4.5-5 × 3.7-4.2 mm, yellow; margins fused from the base to ca ¾ of the column length forming a tubular nectar chamber; nectar chamber 1-1.2 cm long; lateral lobes rounded, margins undulate to crenulate; apical lobe rounded to emarginated, reflexed, margin undulate to slightly crenulate. Column 3.2-3.5 × 0.3-0.32 cm, semicylindrical, slender, sinuous, white, attenuate base, dilated to the apex, with white-hyaline hairs close to the stigma, apex ending in a membranous ochrea; anther 2.9-3 × 2.1-2.5 mm, ovate, white, versatile; rostellum 3.8-4.1 × 2.3-2.6 mm, trapezoidal, membranous, white. Fruits 11-15 × 2.8-3.2 cm, linear, incurved, slightly triangular in transverse section, fleshy.

Distribution and ecology.

Vanilla schwackeana occurs in both gallery forests and mesophytic semideciduous forests from the south of Vale do Rio Doce, eastern Minas Gerais, south-eastern Brazil (Fig. 2 ). Vanilla schwackeana shows a nomadic vine habit, rooting on the forest litterfall, and climbing on tree trunks. The elevation is from 730 to 810 m a.s.l. Each flower lasts ca 12 hours.

Phenology.

Vanilla schwackeana blooms from September to October.

Preliminary IUCN conservation assessment.

Critically Endangered: CR B2ab(i,ii,iii). Vanilla schwackeana is a rare species growing in mesophytic forests in the municipalities of Timóteo and Antônio Dias, southern region of Vale do Rio Doce. The populations only contain a few specimens. The species is known from only three herbarium collections, the holotype without any locality information and two more recent specimens. Since only two specimens have locality data, the EOO (extent of occurrence) cannot be calculated. The area of occupancy (AOO) is estimated to be 8 km2 (cell width 2 km), which falls within the limits for Critically Endangered (CR) under criterion B2 (area of occupancy). The two recent specimens are found in one location, which also falls within the limits of Critically Endangered under subcriterion a. The region where individuals of V. schwackeana are found is being studied for the extraction of iron ore by a mining company. The Vale do Rio Doce has known a long history of deforestation. The region comprises 81 municipalities, 24 of which comprise the "Vale do Aço” (Steel Valley), including Timóteo and Antônio Dias, where exploitation of iron ore has drastically reduced the native flora of the region to sparse forest fragments. I therefore project a continuing decline in (i) extent of occurrence, (ii) area of occupancy, and (iii) extent and/or quality of habitat. Considering these threats and the fact that the species is distributed in one location, V. schwackeana is assessed as Critically Endangered (CR).

Additional material examined.

BRAZIL - Minas Gerais • Antônio Dias, Comunidade Japao, semi-deciduous forest; 19°61 ’15” S, 42°77 ’26” W; 850 m; 6 Oct. 2022; E.R. Pansarin 1567; SPFR • Timóteo, semi-deciduous forest; 19°54 ’59” S, 42°69 ’56” W; 840 m; 7 Oct. 2022; E.R. Pansarin 1568; LBMBP .

Notes.

Based on Hoehne’s hypothesis that the holotype of V. schwackeana is a mixture of elements from distinct Vanilla species and due to the size of the similar floral parts, a dissected flower from the material Schwacke 11106, deposited in the RB herbarium, was designated as the lectotype of V. schwackeana and synonymized under V. planifolia ( Karremans et al. 2020). However, according to my data based on live plants, except for the immature fruit whose characteristics may overlap with those of many Neotropical Vanilla , all other elements present in the material collected by Carl August Wilhelm Schwacke agree with those of the specimens found in the Rio Doce Valley, in the state of Minas Gerais. Therefore, according to the data presented here, there is no mixture of elements in the specimen Schwacke 11106. Based on the fact that Hoehne (1944) described V. schwackeana on the basis of a single collection, I conclude that the collection Schwacke 11106 (RB) is the holotype of V. schwackeana .

Figures

Figure 1. Vanilla schwackeana. A. Part of a plant showing the sinuous stem and distichous leaves. B. Leaf. Note the elliptical shape of the leaf blade. C. Detail of a leaf showing the acuminate apex. D. Apical inflorescence. E. Flower in diagonal view. F. Flower in lateral view. G. Longitudinal section of a flower. The detail (dashed area) shows the labellum base. H. Longitudinal section of part of the labellum. Note the penicillate callus (arrow), the anther (a), and the rostellum (arrowhead). I. Detail of the labellum and column. Note the central crest of the labellum, the penicillate callus, and the anther. J. Dissected perianth. The detail (dashed area) shows the penicillate callus and the central labellar crest. K. Labellum in lateral view. L. Column in lateral view. M. Apex of the column: in lateral view with an articulated anther (above), in lateral view with a disarticulated anther (mid), and in abaxial view (below). Based on E. R. Pansarin 1568 (LBMBP).

Figure 2. Occurrence map of Vanilla schwackeana based on new records from the Vale do Rio Doce region, Minas Gerais, south-eastern Brazil.