Bioacoustics of Appendicula spicata

Distribution: —Endemic to Vietnam : provinces Ha Tinh (Huong Son District), Quang Binh (Minh Hoa District), Thua Thien Hue (districts A Luoi, Huong Thuy, Nam Dong, Phu Loc), Quang Nam (Song Thanh Nature Reserve), Gia Lai (K’Bang District), Dak Lak (Chu Yang Sinh Mountains), Khanh Hoa (Hon Ba Nature Reserve), Ninh Thuan (Ninh Hai District). Conservation status: —In almost all its known locations, Appendicula spicata was observed to be locally common and even abundant. Accordingly, we preliminarily estimate the conservation status of this species as Least Concern (LC). Notes: —For a long time, Appendicula spicata has been misidentified in botanical surveys in Vietnam as A. hexandra ( Seidenfaden 1975 a , 1992, Averyanov 1988 , 1990 , 1994 , 2006 , Ho 1993 , 2000 , Hop 1998 , Averyanov & Averyanova 2002 , 2003). The latter species is known from Thailand , Cambodia , Vietnam and Sumatra ( Comber 2001 , Averyanov 2013 , Averyanov et al. 2016 , Chantanaorrapint 2022 ). The two species can therefore occur sympatrically in Vietnam . These species share superficially fairly similar flowers and are probably connected by natural hybridization, as soon as the plants with intermediate morphology occur; such plants are difficult for identification, particularly in herbarium collections. Meanwhile, living flowering specimens of the new species readily differ from A. hexandra (comprehensive descriptions and drawings of which are presented by Seidenfaden 1992 and Chantanaorrapint 2022 ) in inflorescence 2.5–3.5 cm long, twice as long as the leaves or longer (vs. inflorescence commonly 1.5–2.5 cm long, two times shorter than the leaves or shorter), rachis continuously elongating, many-flowered, usually with more than 30 flowers (vs. rachis not continuously elongating, few-flowered, usually with 2–10 flowers), flowers pure white, lip and column with purple spots on sides (vs. flowers uniformly white with a green tint to light greenish), basal callus of lip almost circular to broadly obovate, with small lateral folds at the base (vs. basal callus of lip oblong ovate, without lateral folds at the base). In addition, flowering shoots of A. spicata curiously resemble those of the predominantly Malesian species A. pendula Blume (1825: 298) , which has long pendulous inflorescences ( Comber 1990 , 2001 , Chantanaorrapint 2022 ). Appendicula spicata differs, however, from the latter species in having much smaller stems and leaves.