NOTES ON RHODODENDRON (ERICACEAE) FROM BALI, INDONESIA, AND A NEW SUBSPECIES OF RHODODENDRON JAVANICUM

In an inventory of Rhododendron species on the island of Bali, Indonesia, three species and two subspecies were recorded. This article presents an identification key to these taxa and brief notes on each taxon. In addition, a new subspecies of Rhododendron javanicum is proposed.

In his monograph, Argent (2015) highlighted the need to assess the taxonomy of Rhododendron javanicum in Bali more comprehensively.He later suggested that the Bali specimens had unique characteristics that supported treating them as a distinct subspecies (George Argent, personal communication, 2018).Unfortunately, until his death, he did not have enough material with which to conduct the necessary assessment.In 2018, a specimen of Rhododendron javanicum from Bali was collected and recognised as the same epiphytic Rhododendron found on the trunks of trees grown in Eka Karya Botanical Gardens, Bali, and previously identified as R. javanicum subsp.teysmannii.However, observation of the specimen in Herbarium Bogoriense (BO; herbarium codes follow Thiers, continuously updated) showed that although the specimen had the same characters as those plants growing in Eka Karya Botanical Gardens, Bali, it also had various morphological characters that differed from Rhododendron javanicum subsp.teysmannii and showed that this new material was sufficiently distinct to be described as a new subspecies.A detailed study of Bali's Rhododendron species is presented here, as is a description of the new subspecies and a key to the taxa, with remarks on their taxonomic history.
Distribution.Java and Bali.In Bali only known from Mount Abang.
Proposed IUCN conservation category (Bali).Globally assessed as Least Concern (LC) (Argent, 2015).In Bali, it is known only from a single specimen in BO from Mount Abang, collected by van Steenis (8033) in 1936.This mountain is a popular area for climbers and as a place of worship for Balinese Hindus.The area is in danger of being damaged by the planned construction of a cable (Suyasa, 2022).Its small population size and plausible future threats from development activities suggest a provisional assessment of Vulnerable (VU) D2 (IUCN Standards and Petitions Subcommittee, 2022).
Habitat and ecology.Terrestrial in montane forests, c.1360 m a.s.l.
Proposed IUCN conservation category (Bali).Globally assessed as Least Concern (LC) by Argent (2015).In Bali, it is known only from Mount Batukaru, an area proposed as a nature reserve by the Indonesian Ministry of Environment and Forestry (Putri, 2012;KSDA Bali, 2019).In addition, the mountain is a popular area for climbers and as a place of worship for Balinese Hindus.The restricted, potentially small population, and plausible future threats from human activities, suggest a provisional assessment of Vulnerable (VU) D2 (IUCN Standards and Petitions Subcommittee, 2022).Shrub.Twigs laxly scaly when young, glabrescent, smooth; internodes 20-90 mm.Leaves 3-7 together in tight pseudowhorls, 30-80 × 12-35 mm, broadly elliptic to ovate, elliptic, apex acute, shortly acuminate or obtuse, margin entire, flat, base broadly to narrowly tapering, initially laxly scaly on both sides, early glabrescent above, laxly or more persistently scaly beneath, sometimes with short hairs above, scales small, dendroid, flat, marginal zone variously, centre brownish to dark, scattered, midvein narrowly impressed above in the proximal half of the leaf, then level with the blade surface, broadly raised beneath proximally but tapering rapidly; lateral veins 5-8 per side, spreading.Habitat and ecology.Found in the granitic upper montane ecosystem at an altitude of 1200-1450 m a.s.l.It is an epiphytic species, and in Eka Karya Botanical Gardens, Bali, it grows in litter-rich trees of Bischofia javanica Blume, Dacrycarpus imbricatus (Blume) de Laub., Glochidion rubrum Blume, Prunus sp. and Syzygium polyanthum (Wight) Walp.(Warseno et al., 2020), as well as in the tree fern Alsophila latebrosa Wall.ex Hook.
Etymology.The epithet honours the late G. C. G. Argent of the Royal Botanic Garden Edinburgh (RBGE) for his lifetime's work on Ericaceae, especially on the genus Rhododendron, and is also in recognition of his mentoring of the first author.
Proposed IUCN conservation category (Bali).Eka Karya Botanical Gardens, Bali, has more than 150 naturally occurring individuals of this species (Warseno et al., 2020).No estimate of numbers of individuals or population on Mount Patas, Mount Pala or Mount Rinjani are available.Although these mountains are popular with mountaineers, there does not appear to be major impact or habitat destruction, and all areas are part of a nature reserve belonging to the Indonesian Ministry of Environment and Forestry and Eka Karya Botanic Garden, Bali.However, the areas are likely to face future challenges due to natural and anthropogenic activities such as forest fires (Undaharta & Sutomo, 2014), and floods have been reported to have happened previously.The negative impact of tourism, agriculture, and invasive alien plant species in the area has also been identified as potentially problematic (Sujarwo, 2019;

Figure 1 .
Figure 1.The distribution of Rhododendron in Bali.Base map from NASA's Earth Observatory.