Rhododendron jaVanicum (Blume) Benn. subsp. argentii Mambrasar, Warseno &, 2024

3. Rhododendron jaVanicum (Blume) Benn. subsp. argentii Mambrasar, Warseno &

Kuswantoro, subsp. noV.

Resembles Rhododendron javanicum (Blume) Benn. subsp. javanicum in its flower shape but differs in its corolla size (25 × 15 mm vs 30–50 × 70–80 mm) and pubescent ovary (vs glabrous to sparsely scaly). It is also similar to Rhododendron javanicum (Blume) Benn. subsp. teysmannii (Miq.) Argent in its flower shape and hairy ovary but differs in its stellately scaly pedicels (vs shortly patently hairy) and leaf size (30–80 × 12–35 mm vs 80–150 × 25–50 mm). It is also close to Rhododendron javanicum subsp. brookeanum in its flower shape but differs in leaf size (30–80 × 12–35 mm vs 120–250 × 35–80 mm) and corolla size (25 × 15 mm vs 50–80 × 50–80 mm). – Type: Indonesia, Bali, Eka Karya Botanic Garden, 10 x 2018, F. Kuswantoro 37 (holotype BO). Figures 2 View Figure 2 , 3 View Figure 3 .

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. Petiole 5–15 × 1–2 mm, without groove, scaly. Inflorescence an open umbel of 3–8, semi-erect to horizontal. Flower buds and bracts not seen. Bracteoles to 10 × 0.5 mm, linear, glabrous. Pedicels 20–30 × 1 mm, laxly, stellately scaly, without hair. Calyx 3–4 mm in diameter, glabrous. Corolla 25 × 15 mm, funnel-shaped, orange to red, glabrous outside, and short hair inside. Stamens to 30 mm long, clustered on the upper side of the mouth of the corolla; filaments 29 mm, linear, densely hairy in the proximal 1/3, glabrous distally, anthers 2 × 1 mm, oblong, curved. Disc prominent, shortly hairy on the upper margin. Ovary 7 × 2 mm, subcylindrical-conical, densely covered with white hair, without scales; style 20 mm, glabrous; stigma c. 1.5 mm in diameter placed on the upper side of the mouth. Fruit 45–50 × 6–8 mm, cylindrical, 5-angled.

Distribution. Known only from Bali (Mount Patas, Mount Pala and Eka Karya Botanical Gardens, Bali) and Lombok Island (Mount Rinjani).

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; Kuswantoro et al., 2020). The restricted distribution, presumably small population size (fewer than 1000 mature individuals), and potential future threat suggest a provisional assessment of Vulnerable (VU) D2 (IUCN Standards and Petitions Subcommittee, 2022).

Notes. The new subspecies was initially interpreted in Sleumer (1960) as a variant of Rhododendron javanicum subsp. teysmannii , a subspecies with a hairy ovary. Two specimens from Bali, R. Maier & Sarip 352 and 455 (BO, L), were included as Rhododendron javanicum var. teysmannii ( Sleumer 1960, 1961, 1963). Because there were no additional specimens at the time, Argent (2006, 2015) and Mambrasar et al. (2019) also followed Sleumer’s revision. Warseno et al. (2002) reported a naturally epiphytic Rhododendron growing in Eka Karya Botanical Gardens, Bali. Because of its epiphytic habit, the plant was nearly considered a new species but was ultimately identified as Rhododendron javanicum . During a visit to BO in 2018, the late George Argent carried out a detailed observation of this unusual epiphytic Rhododendron javanicum from Bali that he thought may be a new species. Unfortunately,

he passed away before his observations were finished. Our detailed observations and comparisons on additional specimens found that specimens from Bali (F. Kuswantoro 37, together with R. Maier & Sarip 352 and 455) have different characters from Rhododendron javanicum subsp. teysmannii . Therefore, these three specimens represent an undescribed new subspecies, which we describe here.

Because the two specimens from Bali (R. Maier & Sarip 352, 455) were excluded from Rhododendron javanicum subsp. teysmannii , the distributional range of R. javanicum subsp. teysmannii becomes limited only to Sumatra and Java, and it is absent in Bali.

Additional specimens examined. INDONESIA. Bali: Mt Pala , 640 m a.s.l., 19 ix 1981, R. Maier & Sarip 352 ( BO) ; Mt Patas , 990 m a.s.l., 20 xi 1981, R. Maier & Sarip 455 ( BO) ; Mt Batukaru, Eka Karya Botanic Garden , 10 x 2018, F. Kuswantoro 37 ( BO) .