Citronella suaveolens ( Blume 1850: 248 ) R.A. Howard (1940: 475)

Nuraliev, Maxim S., Schori, Melanie, Tagane, Shuichiro, Kuznetsov, Andrey N., Kuznetsova, Svetlana P. & Utteridge, Timothy M. A., 2022, Citronella suaveolens, a new generic record for Vietnam, with a key to Vietnamese Cardiopteridaceae, Phytotaxa 532 (1), pp. 67-77 : 68-71

Citronella suaveolens ( Blume 1850: 248) R.A. Howard (1940: 475) ( Fig. 1 , 2 )

Literature:— Howard (1942: 82), Backer & Bakhuizen van den Brink (1965: 59), Sleumer (1969: 187, 1971: 6, Fig. 1 ), Beaman et al. (2001: 381), Utteridge & Schori (2011: 109).

TYPE:— INDONESIA. W Java: s.loc., s.d ., C. L. Blume s.n. (lectotype, designated by Sleumer [1969: 187]: L: L0014727 photo!; isolectotype: U: U.1169894 photo!).

Images of lectotype and isolectotype available at:

https://data.biodiversitydata.nl/naturalis/specimen/L%20%200014727

https://data.biodiversitydata.nl/naturalis/specimen/U.1169894

Heterotypic synonym:

Citronella brassii R.A. Howard (1942: 81) .

TYPE: — INDONESIA. Papua Province: Idenburg [Taritatu] River , 2 km SW of Bernhard Camp, primary rainforest, on slope of ridge , 850 m, 18 March 1939, L. J . Brass, C. Versteegh 13173 (holotype: A: 00050211 photo!; isotypes: BM: BM000839490 photo!, BRI: BRI-AQ0340320 photo!, L: L0014728 photo!).

Additional specimens examined: — VIETNAM. Quang Nam Province: Nam Giang District, Song Thanh Nature Reserve , forest, river bank, 15°34’12’’N 107°22’39’’E, elev. 1050 m, 30 April 2019, M. S. Nuraliev 2448 ( MW: MW0757764 , MW0757765 ; photo LE: LE01093242 http://en.herbariumle.ru/?t=occ&id=108748) ; Quang Nam Province: Nam Giang District, Song Thanh Nature Reserve , forest, river bank, 15°32’08’’N 107°23’10’’E, elev. 1070 m, 01 May 2019, M. S. Nuraliev NUR 2451a (photo LE: LE01093243 http://en.herbariumle.ru/?t=occ&id=108749) .

Distribution:— Vietnam (Quang Nam Province: Song Thanh Nature Reserve), Sumatra (Simeulue Island), Java, Borneo, Sulawesi, the Maluku Islands, New Guinea.

Notes: —The Vietnamese population of Citronella suaveolens reported here ( Fig. 3 ) is more than 1400 km distant from the known locations of the species in Sumatra and Borneo. The finding represents a significant range extension of the genus Citronella and its first known occurrence from mainland Southeast Asia.

This disjunct population of Citronella provides another example of the taxa recently discovered in Eastern Indochina and previously known only (or mostly) from Malesia and further south; see Appendix 1 for a list. The considerable overlap of floristic elements between Eastern Indochina and such Malesian regions as Peninsular Malaysia, Borneo, Sumatra and Java presumably reflects connection of these regions as parts of Sundaland during glacial periods.

Ecology and phenology:— Citronella suaveolens inhabits various types of primary forests at elevations of 0– 1600 m a.s.l. In the Song Thanh Nature Reserve, Vietnam, it is common in a primary, mid-mountain, weakly disturbed forest along rivers. A description of vegetation in this forest complex is provided by Vislobokov et al. (2019).

Flowering in Vietnam: April–May.

Brief field observations made by the first author suggest predominantly nocturnal flowering, or at least flower opening, in C. suaveolens . During the daytime (including morning hours, Fig. 1D , 2F , and evening hours, Fig. 1C , 2D, E ), the inflorescences bear flowers at late anthesis, showing petals with signs of withering and strongly reflexed apices, and strongly exserted stamen filaments reflexed outwards between the free petals. Anther thecae present pollen in the morning ( Fig. 2F ) and are dried and empty in the evening ( Fig. 2D, E ). In cut branches awaiting herbarium preparation, simultaneous flower opening (one flower in each cincinnus) occurred around 23:00 ( Fig. 2A, C ). The freshly opened flowers had erect stamen filaments not reflexed outwards from the corolla, filaments not fully elongated (distinctly shorter than petals), and undehisced or just dehisced anthers.

Figures

FIGURE 1. Citronella suaveolens. A. Branch with inflorescences. B. Leaf, abaxial surface. C, D. Inflorescences. Nuraliev 2448 (A–C) and Nuraliev NUR 2451a (D). Photos and design by M. Nuraliev.

FIGURE 2.Citronella suaveolens, floralstructure and phenology.A. Inflorescence at nighttime,showing opening flowers.B. Inflorescence branch (a cincinnus). C. Flower at early anthesis, top view (around 23:30). D. Flower at late anthesis, top view (around 16:30). E, F. Flowers at late anthesis, side view; three petals and two stamens removed to show pistil in E. Nuraliev 2448 (A–E) and Nuraliev NUR 2451a (F). Photos and design by M. Nuraliev.

FIGURE 3. Distribution map of Citronella suaveolens in Vietnam.