Bioacoustics of Vanilla cardinalis

Distribution :— Vietnam , Phu Yen Province (Song Hinh District). Endemic of southern Vietnam in limits of the eastern coastal part of the South Indochinese floristic province ( Averyanov & Averyanova 2003 , Fu et al. 2019 ); known from a single location. Characters Vanilla cardinalis Vanilla sumatrana Sepals: shape narrowly obovate broadly oblanceolate length 2.4–2.9 cm 3.9 cm Petals: shape narrowly obovate broadly oblanceolate length 2.4–2.7 cm 3.75 cm Lip: colour ground colour light yellowish, heavily marked with bright bloody red blotches and bright bloody light yellow to yellow with dark purple veins red along veins, with pure white bunch of bristles on central callus and hairs at lip apex length 2.3–2.7 cm 3.5 cm width 2.6–2.9 cm 3.1 cm shape of median lobe half circular, flabellate oblong narrowly ovate apex of median lobe deeply emarginate; between lobules with a bundle very shortly bilobed; at center with a cushion of numerous soft flexuose, somewhat fleshy hairs covered with dense short hairs 1–2 mm long 4–5 mm long length of median lobe 7–8 mm 6.7 mm width of median lobe 14–16 mm 7.5 mm central callus bearing dense bunch of numerous scarious bristles bearing several thin imbricate scarious transverse plates Column: length 1.2–1.4 cm 2.65 cm Conservation status :—Estimated as critically endangered: CR (B1, B2a, C1, D). Our field studies and observations indicate that V. cardinalis meets the following IUCN (2019) Red List criteria: only one population is discovered with extent of occurrence less than 100 km 2 (B1) and area of occupancy less than 10 km 2 in one known location (B2a), the population includes less than 250 mature individuals with estimated decline of their number at least on 25% in 1 generation (C1), and population is very small with estimated number of mature individuals less than 50 (D). Notes :—We assign Vanilla cardinalis to V. subgen. Xanata Soto Arenas & Cribb (2010: 358) sect. Tethya Soto Arenas & Cribb (2010: 359) . Within this section, the new species belongs to the so-called V. kinabaluensis group (sensu Soto Arenas & Cribb 2010 ), together with such Vietnamese species as V. siamensis and the recently described V. atropogon and V. tiendatii ( Schuiteman et al. 2013 , Nguyen et al. 2020 ). Species of this group share such diagnostic features as broadly elliptic leaves, terete stems, multi-flowered racemose inflorescences, stout ovary, thick and relatively short fruit, uniformly greenish-yellow tepals, and lip cuneate-flabellate, trumpet-shaped, not unguiculate, more or less trilobed, with recurved median lobe bearing bunch of fleshy hairs or long fleshy papillae. This group is distributed from S China to New Guinea , with the highest species diversity in Indonesia ( Soto Arenas & Cribb 2010 ). Vanilla cardinalis is morphologically distinct from all the species of the genus known in eastern Indochina ( Cambodia , Laos and Vietnam ) and is unlikely to be closely related to any of them. Among the species of V. subgen. Xanata sect. Tethya , the new species is similar to V.sumatrana J.J. Smith (1920: 22) , also a member of the V.kinabaluensis group, and V. griffithii Reichenbach (1854: 88) belonging to the V. griffithii group ( Soto Arenas & Cribb 2010 ). In particular, the three species share a trilobed lip with emarginate median lobe. Vanilla cardinalis is most close to V. sumatrana endemic to Sumatra ( Smith 1920 , Comber 2001 ), but differs from the latter in smaller flowers, narrowly obovate (vs. broadly oblanceolate) sepals and petals, median lobe of lip half circular, flabellate, 7–8 mm long, 14–16 mm wide, deeply emarginate (vs. oblong narrowly ovate, 6.7 mm long, 7.5 mm wide, with very shortly bilobed apex), central callus bearing dense bunch of numerous scarious bristles (vs. bearing several thin imbricate scarious transverse plates), lip apex between lobules of median lobe with a bundle of numerous soft flexuose, somewhat fleshy hairs 4–5 mm long (vs. median lobe at center with a cushion covered with dense short hairs 1–2 mm long), lip almost entirely bright bloody red (vs. with dark purple veins). Detailed comparison of the two species is presented in the Table. It is noteworthy that the new species is readily recognized among almost all the species of V. sect. Tethya by its small flowers and predominantly red lip. Vanilla cardinalis is similar to Miguelia cruenta , Vanilla atropogon and V. yersiniana in being a very rare local endemic of the eastern part of the South Indochinese floristic province ( Averyanov et al . 2003 , Fu et al. 2019 ). The only known location of the new species obviously requires protection to assure conservation of this remarkable plant.