Vanilla argentina Hicken

Pansarin, Emerson R., 2025, Systematics of the Vanilla chamissonis clade (Orchidaceae): a study based on integrative taxonomy, Plant Ecology and Evolution 158 (2), pp. 260-278 : 260-278

Vanilla argentina Hicken ( Hicken 1917: 235)

Figs 1 , 4 , 6 , 5 , 7 , Table 1

Type

ARGENTINA – Formosa • Pilcomayo ; 23 Sep. 1915; J. A. Domínguez 305; lectotype (designated here): SP! [ SP 45706 B ]; isolectotype: SI not found .

Description

Nomadic vines, long scandent. Roots axillary, one per node; terrestrial roots up to 8 mm diam., fleshy, whitish, with hyaline absorbing hairs; aerial roots 2.2–2.5 mm diam., whitish to brownish. Stem climbing, cylindrical, fleshy, straight to sinuous, glabrous, glaucous to dark green, strongly furrowed under arid conditions; internodes of ascendant stems 4–16 × 0.5–10 cm. Leaves 6–22 × 3–5.5 cm, alternate, distichous, elliptic to lanceolate, symmetric to asymmetric, fleshy, glabrous, green, pseudopetiolate, margin entire, base attenuate, apex acuminate; pseudopetiole 5.5–8 mm concave. Inflorescence axillary, racemose, with up to 14 flowers opening in succession; 1–2 flowers opening each morning; rachis 5–15.5 × 0.8–1.3 cm, terete, glaucous to dark green; bracts 5–9 × 4–7.5 mm, progressively smaller toward the apex, triangular to ovate, coriaceous, concave, green, erect to patent, apex acute, not incurved. Flowers resupinate, pedicellate, abscission layer between perianth and ovary present; pedicel with ovary 45–50 × 3–4 mm, trigonous in transverse section, white at the base, green to the apex, with a calyculus (6–6.5 × 2.5–3) at the apex. Sepals 6.8–7.4 × 1.2–1.4 cm, free, oblanceolate, fleshy, slightly concave, spreading, pale green to yellowish, margin entire to the apex and involute at the base, base attenuate, apex acute, somewhat thickened; dorsal sepal symmetric; lateral sepals asymmetric; base slightly incurved. Petals 6.6–7.1 × 1.2–1.5 cm, free, obliquely linear, asymmetric, lower margin more arcuate, membranous, pale green, base attenuate, apex acute to obtuse, adaxial surface with a central and longitudinally disposed keel. Labellum 1 - lobed to slightly 3 - lobed, 6.7–7.4 × 3.8–4.2 cm, tubular, deepening near the middle, yellowish to the base, white in distal portion, unguiculate, with a central crest from the unguiculus to the apex, and a penicillate callus just below the anther; unguiculus fused along the margins of the basal half (ca 30–35 mm) of column length forming a nectar chamber, nectar chamber 1.8–2 cm long, tubular; central crest yellowish from the nectar chamber to the penicillate callus, dark yellow to the apex; distal portion of the central crest swollen, low cushion, rugose-papillose at the apex, with a group of transversal yellow-orange scales near the penicillate callus, with five yellow longitudinal lines near the apex; penicillate callus 5.2–6 × 4.4–4.7 mm, made by yellow-hyaline lacerate-laciniate scales and clusters of trichomes; lateral lobes not much evident, rounded, overlapping the column apex, margin undulate; midlobe deeply emarginated; margin undulate. Column 38–40 × 4.5–5 cm, trigonous, arched to the base, forming an angle ca 90 ° with the ovary, strait to the apex, ventral surface flat with white to yellowish hyaline trichomes over the distal half, attenuate to the base, dilated to the apex, with two lateral wings; lateral wings rounded, bilobed, undulate. Stigma bilobed; rostellum 5–5.2 × 3.7–3.9 mm, trapezoidal, membranous, white. Anther 5.8–6 × 4.7–4.9 mm, rectangular to trapezoidal, white, versatile, apex truncate; pollen mass 3.2–3.3 × 3.5–3.8 mm, triangular, bipartite, yellowish. Fruits 11–16 × 2.3–2.8 cm, oblong, straight, transversally trigonous, fleshy, brown and indehiscent when mature, fragrant; pericarp half hard; fruit cavity hollow. Seeds ca 0.5 mm, ovoid, black.

Distribution and ecology

Vanilla argentina occurs in Cerrado areas in Argentina, Brazil, and Paraguay (Fig. 4 ). The species is commonly found in gallery forests, at elevation is from 657 to 850 m a. s. l. Vanilla argentina has a nomadic vine habit, commonly rooting on the forest litterfall, and climbing on tree trunks. The flowers are fragrant. Each flower lasts ca 1 day. The fruits ripen 18 months after pollination. The fruits are indehiscent and have an unpleasant aroma and a bitter flavour.

Phenology

Vanilla argentina blooms from October to December. The fruits ripen from May to July.

Preliminary IUCN conservation assessment

Endangered: EN B 2 ab (i, ii, iii). Vanilla argentina is an uncommon and rarely collected species currently known to grow in Cerrado areas of southeastern and central-western Brazil and Dry Chaco vegetation in Argentina and Paraguay. The populations are composed of few sparse specimens. The extent of occurrence (EOO) is estimated to be 1,344,031 km 2, which falls within the limits for Least Concern (LC) under criterion B 1, according to the IUCN Red List categories and criteria. The area of occupancy (AOO) is estimated to be 80 km 2, which falls within the limits for Endangered (EN) under criterion B 2. Considering that the Cerrado areas have been reduced to scattered fragments due to the expansion of soybean and sugar cane crops and the transformation of native areas into pastures lands, I project a continuing decline in (i) extent of occurrence, (ii) area of occupancy, and (iii) extent and / or quality of habitat for V. argentina . Based on these threats and the fact that the species is distributed in less than five locations, V. argentina is assessed as Endangered: EN B 2 ab (i, ii, iii).

Additional material examined

ARGENTINA – Misiones • San Pedro , Catamarca; 26°37’45”S, 54°06’48”W; 548 m; Dec. 1916; T. Rojas 2040; SP .

BRAZIL – Distrito Federal • Brasília, Parque Nacional de Brasília, Cascalheira do Exército ; 15°46’48”S, 47°55’45”W; 16 Sep. 2018; C. R. Martins 3054; CEN • FERCAL - APA da Cafuringa, a 38 km do CENARGEN ; 15°46’48”S, 47°55’45”W; 910 m; 9 Aug. 1990; T. B. Cavalcanti 598; CEN • Taguatinga, Floresta Nacional de Brasília (Área 1) ; 15°50’00”S, 48°03’23”W; 1200 m; 23 Nov. 2007; J. H. Lima 32; UB . – Goiás • Campos Belos, Estrada velha de São Domingos para Campos Belos ; 13°01’31”’S, 46°45’54”’W; 652 m; 22 Oct. 2001; M. L. Fonseca 3002; IBGE • Cristalina, Margem direita do Rio Preto ; 16°46’4”S, 47°36’47”W; 1237 m; 12 Aug. 2002; A. Amaral-Santos 1367; CEN • Formosa, Ribeirão Bezerra ; 15°32’13”S, 47°20’09”W; 911 m; 8 Oct. 2002; E. Tameirão Neto 3567; BHCB • Morrinhos, Rodovia Morrinhos-Caldas Novas ; 17°43’16”S, 49°06’29”W; 768 m; 4 Sep. 1976; G. Hatschbach 38915; MBM . – Mato Grosso • Nova Xavantina, ca 70 km N of Xavantina ; 14°22’S, 52°37’W; 300–400 m; 10 Oct. 1964; H. S. Irwin 6750; NY . – Mato Grosso do Sul • Campo Grande ; 20°26’37”S, 54°38’52”W; 612 m; 15 Nov. 2023; E. R. Pansarin 1573; LBMBP . – Minas Gerais • Belo Horizonte, Campus da UFMG ; 19°48’57”S, 43°57’15”W; 5 Nov. 1994; V. A. de Sousa s. n.; BHCB 24796 • Diamantina, Serra do Espinhaço ; 18°14’17”S, 43°36’40”W; 975 m; 17 Apr. 1972; H. S. Irwin 28146; NY • Serra do Espinhaço, Mata Ciliar ; 18°14’17”S, 43°36’40”W; 970 m; 25 Oct. 2023; E. R. Pansarin 1571; LBMBP • Mariana, Mina da Samitri ; 20°22’41”S, 43°25’00”W; 718 m; 28 Nov. 2000; R. C. da Mota & L. Viana 570; BHCB • Paracatú, Cerrado, ca 5 km S. E. of Paracatú ; 17°13’21”S, 46°52’31”W; 650 m; 6 Feb. 1970; H. S. Irwin et al. 26210; UB • Pimhuí ; 20°27’42”S, 45°56’45”W; 818 m; 1 Nov. 2023; E. R. Pansarin 1572; LBMBP • São Gonçalo do Rio Abaixo ; 19°49’41”S, 43°22’55”W; 743 m; 21 Oct. 1993; E. L. Borba 79; BHCB . – São Paulo • Itirapina, Itaqueri da Serra, Mata de Galeria ; 22°15’10”S, 47°49’22”W; 817 m; 22 Oct. 2023; E. R. Pansarin 1569; LBMBP • Itirapina, Itaqueri da Serra, Mata de Galeria ; 22°15’10”S, 47°49’22”W; 817 m; 29 Oct. 2023; E. R. Pansarin 1570; LBMBP • Itú, Capão Sombrio ; [23°15’57”S, 47°17’57”W]; 577 m; 20 Dec. 1897; A. Russel CGG 3840; SP • São José do Rio Preto, Estação Ecológica do Noroeste Paulista ; 20°43’36”S, 49°22’50”W; 410 m; 10 Oct. 1996; W. Forster 9; SJRP .

PARAGUAY • Cordillera de Altos; 25°16’55”S, 57°38’6”W; 7 Dec. 1902; K. Fiebrig 564; F .

Notes

Vanilla argentina has been considered synonymous with V. chamissonis , the latter assumed to be a species widely distributed throughout South America. However, some authors have observed differences between specimens collected inland compared to those occurring on the coast. Such differences have resulted in the publication of two taxa, Vanilla argentina and V. chamissonis var. longifolia , the latter being invalidly published, as F. C. Hoehne providing a diagnosis in Portuguese instead of Latin ( Turland et al. 2018). My data, based on specimens collected in Cerrado areas in the states of São Paulo, Minas Gerais, and Goiás, show that the plants of some populations have long and dark green leaves that are quite distinct from those from populations in the Gran Chaco. Specimens with long leaves strongly agree with those of V. chamissonis var. longifolia . However, the flowers and fruits are identical. In addition, ITS DNA sequences align perfectly with those of V. argentina . For this reason, the long- and short-leaved plants are treated here as single taxon, V. argentina .

Morphological affinities

Vanilla argentina is distributed in the Dry Chaco and Cerrado (Fig. 4 ). The species is recognized by its commonly elliptic leaf blades (Fig. 5 ). Plants from some Cerrado areas in São Paulo, Goiás, and Minas Gerais (southwestern and central-western Brazil) commonly have long lanceolate leaves. However, this appears to be intraspecific variation, as populations with leaves morphologically similar to those plants found in the Dry Chaco are also found in the Brazilian Cerrado. Apart from vegetative variations, flowers from plants of both biomes are morphologically indistinguishable. Flowers of V. argentina are recognized from the remaining species of the V. chamissonis clade by its sepals 6.8–7.4 cm long, linear petals 6.6–7.1 cm long, labellum 6.7–7.4 cm long with a nectar chamber 1.8–2 cm long and a column 38–40 mm long, and fruits with a half hard pericarp (Figs 6 – 7 ). All morphological characteristics support V. argentina as a member of the V. chamissonis clade, which is corroborated by the phylogenetic analysis (see further).

Figures

Figure 1. Vanilla argentina Hicken. A. Part of a flowering plant showing the stem, leaves, and inflorescence. B. Flower in diagonal view. C. Flower in lateral view. D. Flower in front view. E. Dissected perianth. The details (dashed areas) show the central labellar crest (left) and the penicillate callus (right). F. Detail of the adaxial surface of a petal showing the longitudinal keel. G. Detail of the apex of the labellum showing the yellowish longitudinal crest with five longitudinal ribs and the lateral lobes overlapping the column apex. H. Pedicel / ovary, column, and labellum in lateral view. I. Pedicel / ovary and column in lateral view. J. Apex of the column: in lateral view with an articulated anther (above), in abaxial view (mid), and in lateral view with a disarticulated anther (below). K. Anther in dorsal view (left) and ventral view (right). L. Pollen mass in dorsal view (left) and ventral view (right). M. Mature fruit. N. Transversal section of a mature fruit. Note the hollow fruit cavity. Based on E. R. Pansarin 1570 (LBMBP).

Figure 4. Occurrence map of Vanilla argentina, V. chamissonis, and V. calyculata.

Figure 5. Comparative morphology of leaves of related Vanilla species. A. V. argentina. B. V. calyculata. C. V. chamissonis. Scale bars = 2 cm. A from E. R. Pansarin 1570 (LBMBP), B from VAN 206 (Vanilla germplasm bank, LBMBP Orchid House), C from E. R. Pansarin 1579 (LBMBP).

Figure 6. Comparative morphology of perianth parts of related Vanilla species. A. V. argentina. B. V. chamissonis. C. V. calyculata. Lowercase letters on the right side of the floral parts are: (a) distended labellum, (b) labellum apex, (c) detail of the labellar crest, (d) petal. Scale bars = 2 cm. A from E. R. Pansarin 1570 (LBMBP), B from E. R. Pansarin 1579 (LBMBP), C from VAN 206 (Vanilla germplasm bank, LBMBP Orchid House).

Figure 7. Comparative morphology of mature fruits of related Vanilla species. A. V. argentina. B. V. chamissonis. C. V. calyculata. Details in figures are transversal (A, B) or longitudinal (C) sections of mature fruits. Scale bar = 2 cm. A from E. R. Pansarin 1570 (LBMBP), B from E. R. Pansarin 1579 (LBMBP), C from VAN 206 (Vanilla germplasm bank, LBMBP Orchid House).