Vanilla cameroniana Damián, 2023

Damián-Parizaca, Alexander & Mitidieri-Rivera, Nicole, 2023, Vanilla cameroniana (Orchidaceae, Vanilloideae), a new species from French Guiana and new records from the Guiana Shield, Phytotaxa 609 (3), pp. 222-232 : 223-227

Vanilla cameroniana Damián , sp. nov. ( Figures 1 , 2A , 3A )

Type:— FRENCH GUIANA. Saint-Georges: Regina, Petite Montagne Tortue , 52 13’ O 4 18’ N, 10 June 2005, D. Sabatier & M.-F. Prevost 4912 (holotype: SEL047233!).

Vanilla cameroniana superficially resembles V. appendiculata Rolfe (1895: 178) but may be easily distinguished by the conspicuously petiolate broader leaves up to 12 cm wide (vs. sub-sessile, up to 5.9 cm), axillary inflorescence (vs. apical), greenish sepals and petals (vs. white) narrow linear petals, 2–3 mm width (vs. narrowly lanceolate, 5–8 mm), unlobed lip (vs. trilobed), and sub-quadrate apex with a trullate-shaped structure close to the apex made of short appendages (vs. ovate with long lombricoid appendages).

Description:— Hemiepiphytic herb, leafy, that branches out as it grows up to 2 m long (at least). Stems flexuose, terete, dark green, 1.0– 1.2 cm wide (0.3–0.4 cm when dried); internodes 6–7 cm long. Aerial roots, terete, greenish, 0.9–1.5 × 0.2–0.3 cm. Leaves green, with a distinct petiole, 2–3 cm long, shiny; blade strongly obovate, base attenuate, apex cuspidate, membranaceous, becoming light brown after herborization, margins entire, mid-vein sulcate, veins conspicuously reticulate, 14–27 × 6–12 cm. Inflorescence axillary, racemose, successively 1-flowered; peduncle 0.2 cm long, rachis 1.5 cm long; bracts of the inflorescence light green. Floral bracts broadly ovate, convex, reticulate, 0.3–0.5 × 0.2–0.3 cm. Flowers resupinate, pendular, sepals and petals pale green or light green, lip white, light green abaxially close to the base. Ovary pedicellate, terete, sinuous, curved, something sigmoid, 1.5–3.0 × 0.2 cm including the pedicel. Dorsal sepal lanceolate; margins entire, revolute; base truncate, apex acuminate, apically twisted, 8–9– veined, 6.0–6.5 × 0.6–0.65 cm. Lateral sepals similar to the dorsal sepal in shape, 10–11-veined, 6.0–6.5 × 0.8–1.0 cm. Petals linear; margins entire, apex acute, recurved, abaxially with a longitudinal prominent keel, abaxially sulcate along the midvein, 7–8-veined, 6.0–6.3 × 0.2–0.3 cm. Labellum white, adaxially light green turning darker towards the base, adnate with the column for 5.4 cm, the edges inrolled and touching each other which makes the dorsal side of the column not visible from outside the flower, 6.9 × 3.8 cm, unlobed, overall fan-shaped and forming a tube in its natural position, the margins gradually change from entire to erose and sinuate at the apex, narrowly channeled abaxially, attenuate at the base where attached to the column, with two parallel low keels flanking the penicillate callus that appear close to the middle and fade away close to the apex; lateral portions of the lip shoulder-shaped, broad, orbicular, margins entire to minute undulate; apex white overall, subquadrate, with a trullate-shaped structure close to the apex made of appendages 0.2 cm long, minutely papillose; penicillate callus made up by 8 congested, retrorse, trapezoidal, laciniate scales, the scales free from each other, 4–5 × 3 mm; the region just after the penicillate callus, smooth. Column white, 5.5 × 0.3 cm, erect, ventral surface glabrous; apex dilated, 5 mm, the apex winged with a horned clinandrium. Stigma lateral lobes are hard to distinguish and covered by a stigmatic sticky fluid in our sample, rostellum ca 5 × 3 mm, convex, quadrate, margins entire, revolute. Anther 4.8 × 3.6 mm, saddle-shaped, with two hornshaped projections and with pollen grains not forming a pollinarium but two granular masses. Fruit not seen.

Distribution and ecology:—So far known from three collections in the arrondissements of Roura and Regina where the species has been recorded to inhabit secondary and swamp forests at 10–100 m in elevation ( Figure 4 ). Vanilla cameroniana features a penicillate callus and conspicuous floral tube formed by the fusion of the labellum and column. Based on existing evidence, it is reasonable to propose that this species is likely pollinated by the same mechanism as observed in other Vanilla subgen. Xanata members, which are known to be pollinated by Euglossine bees ( Ackerman et al. 2023, Cameron 2003).

Etymology:— Vanilla cameroniana is named after Kenneth M. Cameron, Professor of Botany at the University of Wisconsin-Madison and Director of the Wisconsin State Herbarium (WIS), to honor his unparallel contributions to our understanding of the subfamily Vanilloideae subfamily, and specifically of Vanilla . Dr. Cameron’s efforts in unraveling the intricate and unique adaptations of Vanilla species have yielded invaluable insights into the evolutionary history and ecological roles of these captivating orchids and made the subfamily an outstanding model system for the study of plant evolution.

Additional specimens examined:— FRENCH GUIANA; Camp Caiman-Asarco-Mt de Kaw, 4 41’ 720’ N, 52 13’386” W, 10 m, Foret Marecageuse zone collins isolees-swamp forest in isolated hills area, January 17, 2000, Bordenave B., N. Raes & L. Betian 4960 [sterile] (U0112153).

Taxonomic Discussion:— Vanilla cameroniana belongs to Vanilla subgenus Xanata due to its distinctive penicillate callus and connate lip margins. Among the Neotropical members of Vanilla subgen. Xanata species, V. appendiculata stands out as one of the species that resembles V. cameroniana morphologically. It shares the obovate leaves and midlobe lip appendages with V. cameroniana ( Figure 3 A, C ). However, they can be easily distinguished based on the features outlined in the diagnosis. Another species, V. sprucei , exhibits similarities in flower color (light green tepals and white sepals) and linear petals (1–3 mm wide), which is rare among Vanilla species. Vanilla cameroniana differs in having unlobed lip with dense lombricoid appendages apex, as opposed to the trilobed lip with a cushion-like apex found in V. sprucei ( Figure 3 A, D, E ) ( Table 1 ). Vanilla hartii Rolfe (1899: 151) , another species described from Guyana, shares some resemblance to V. cameroniana , but can be readily differentiated by its smaller flowers with a trilobed lip measuring 3.7–4.3 cm in length, in contrast to the unlobed lip of V. cameroniana measuring up to 6.9 cm. Furthermore, V. hartii has low papillose grooves at the apex instead of conspicuous long appendages ( Figure 3 A, B ). Lastly, V. bicolor is a distantly similar species that can be distinguished from V. cameroniana by its smaller leaves (5–11 × 2.5–4.5 cm vs. 14–27 × 6–12 cm) and lip with a diffuse penicillate callus, unlike the well-defined penicillate callus seen in V. cameroniana .

We decided to include a sterile specimen (Bordenave et al. 4960) in our concept of V. cameroniana due to its obvious vegetative resemblance and geographical proximity (<20 km apart) to the holotype ( Figure 2B ). As far as our knowledge goes, Vanilla cameroniana is the only species within neotropical Vanilla species that bears the combination of long-petiolated, membranaceous, obovate, strongly reticulate leaves, a consistent characteristic found among the three records we have examined. Among the nineteen species currently recognized inside Vanilla subgen. Vanilla ( Karremans et al. 2020, Damian et al. 2022), all featuring membranaceous and strongly reticulate leaves, none exhibit the conspicuous obovate leaves found in the Bordenave specimen. Although there are some species within the Vanilla subgen. Xanata with obovate leaves, such as Vanilla appendiculata and Vanilla marowynensis Pulle (1906: 118) , they differ by having conspicuous coriaceous leaves (see Figure 25, Damian & Janovec 2018; and Figure 23, Karremans et al. 2020). Vanilla dressleri and Vanilla trigonocarpa Hoehne (1944: 139) , occasionally have obovate leaves, but the former distinguishes from V. cameroniana by having thick leaves up to 6.5 cm wide (compared to membranaceous, up to 12 cm); and the latter, while typically membranaceous, has a blade not wider than 7 cm and long acuminate leaves, in contrast to the up to 12 cm wide and cuspidate leaves of V. cameroniana ( Soto Arenas & Dressler 2010) . Additionally, none of these species have long-petiolated leaves that reach up to 3 cm like V. cameroniana , a feature that is consistent in the sterile specimen. Therefore, based on this evidence we conclude that the Bordenave specimen is conspecific with our concept of Vanilla cameroniana .

Figures

FIGURE 1. Line drawingof Vanilla cameronianabased on the FrenchGuiana holotype.A.Habit.B. Leaf adaxial surface.C. Inflorescence. D. Flower, E. Dissected perianth. F. Lip. G. Pubescent detail at the base of the lip. H. Penicillate callus. I. Detail of the lip apex. J. Anther. K. Column with and without anther. Drawing by N. Mitidieri based on A, D iNaturalist record and B, C, E–K Sabatier D. & Prevost M.-F 4912 (SEL).

FIGURE 2. Herbarium specimens studied of Vanilla cameroniana Damián. A. Holotype, Sabatier D. & Prevost M.-F 4912 (SEL047233). © copyright of the Marie Selby Botanical Gardens Herbarium (SEL). B. Bordenave B., N. Raes & L. Betian 4960 (U0112153) © copyright of the Naturalis Biodiversity Center, Leiden.

FIGURE 3. Labellum comparison of morphological similar species. A. to V. cameroniana. B. V. hartii. C. V. appendiculata. D–E. V. sprucei. Based on (A) Sabatier D. & Prevost M.-F 4912 (French Guiana, SEL), (B) Stevens 20021 (Nicaragua, SEL), (C) J. Pizango JPF003 (Perú, USM), (D) Redden 1843 (Guyana, US), (E) Redden 2518 (Guyana, US). Photographs by A. Damián (A, B, D, E) and N. Mitidieri (C).

FIGURE 4. Geographic distribution of the species discussed in this study, including the limits of the Guiana Shield. The black-colored datapoints on the map represent occurrences documented in the GBIF database, while the blue-colored datapoints indicate new records reported in this study. Additionally, red datapoints represent the newly described species. The asterisk (*) is used to indicate type material.