Ardisia pyrotechnica Julius, Tagane & Utteridge, 2021

Julius, Avelinah, Tagane, Shuichiro, Kajita, Tadashi, Jelani, Nur Safinas, Mohamad, Mohizah & Utteridge, Timothy M. A., 2021, Ardisia pyrotechnica (Primulaceae-Myrsinoideae), a new species from Borneo, Phytotaxa 507 (2), pp. 205-210 : 206-209

Ardisia pyrotechnica Julius, Tagane & Utteridge , sp. nov. (subgenus Pyrgus) Figs. 1‒2

Among the Bornean members of subgenus (§) Pyrgus, the new species is most similar to Ardisia breviramea in having large foliose bracts, being hairy on inflorescences and the pinkish-white flowers, but A. pyrotechnica differs especially in the massive inflorescences up to 26 cm long and branched to 3 orders (vs. 8 cm long and to 2 orders in A. breviramea ), the larger sepals up to 10 mm long, elliptic to narrowly elliptic and slightly overlapping at base (rather than smaller, 4.5–6 mm long, oblong-elliptic and not overlapping at the base in A. breviramea ).

Type:— MALAYSIA. Borneo: Sarawak, Miri District , Lambir Hills National Park , on the way to Latak Waterfall , lowland dipterocarp forest, 04°11′56.4″N, 114°01’41.7″E, 87 m elev., 18 July 2016 (fl.), T. Yahara, S. Tagane & K. Fuse SWK1910 (holotype SAR!; isotype FU!) .

A woody shrub to 4 m high. Indumentum of short, white, simple hairs, with glands on reproductive parts. Leaves spirally arranged, somewhat condensed at the stem apex; petiole (5–)10–15(–30) mm long, winged by the decurrent leaf base, glabrous; lamina thinly coriaceous, with brown gland-dots throughout the leaf, slightly bullate, elliptic to oblanceolate-elliptic, 27–34 × 11–14 cm, base long attenuate or cuneate, margin entire but recurved when dry, apex acute to shortly acuminate, with acumen 1–1.5 cm long, glabrous on both surfaces; midrib flat with slightly raised in the middle above, raised below; lateral veins 11–16 pairs, and sometimes with 1–2 intersecondary veins within each pair, prominent on both surfaces, arcuate and joining near margin; intercostal veins reticulate, prominent and visible on both surfaces when dry. Inflorescences terminal on specialised lateral branches, arising directly from the stem (not in the axils of leaves or fallen leaves), branch leafless except for a pair of foliose inflorescence bracts subtending the inflorescence, bracts elliptic to elliptic-obovate, 30–34 × 11–14 cm, apex acute to slightly acuminate, inflorescence paniculate, 25–26 cm long, 3 times branched; rachis slightly flexuous, covered with minute glandular hairs; floral bracts sparsely covered with brown gland-dots, oblong-elliptic, 5–10 × 1–3 mm, apex acute, densely hairy on both surfaces. Flowers racemose; pedicels slender, 1–1.2 cm long, hairy as in rachis of inflorescences; sepals pinkish-white, 5, elliptic to narrowly elliptic, 7–10 × 3–4 mm, apex acute, overlapping at base, densely hairy on both surfaces; corolla pinkish-white, covered with sparse, brown gland-dots towards apex, deeply lobed, lobes 5, ovate, c. 6 × 5 mm, with long acuminate apex, glabrous on both surfaces; anthers yellow, 3 × 1.5 mm, covered with dense gland-dots in the middle abaxially, filament c. 1.5 mm long; ovary subglobose, 1 × 1 mm, glabrous, style 1.5–5 mm long, glabrous, stigma not conspicuous. Fruits young globose, mature ones not seen; ovules c. 10 in 1-series.

Phenology:— Flowers collected in April and July, and immature fruits in May and July.

Habitat:— Grows in lowland dipterocarp forest and limestone hill areas.

Etymology:— The species epithet refers to the large, pinkish-white, spreading inflorescences that resemble an exploding firework.

Provisional conservation status:— Critically Endangered (CR B1a & bi, iii and D). To date, Ardisia pyrotechnica is known only from three collections from two localities, within the protected area of Lambir Hills National Park and Niah National Park, Miri District, northern Sarawak. Based on these records, the area of occupancy (AOO) for this species is calculated as 12 km 2 (using a 2 km cell width) and the Extent of Occurrence was 56.3 km 2. The species might be more widely distributed in adjacent areas, but most areas, especially lowland forest, have been deforested for oil plantation and two localities are fragmented. In Lambir Hills National Park, we found only two individuals, from which we collected the above specimens. Though the National Park has been well-studied botanically and ecologically ( Inoue 1997, Lee et al. 2002), there are no specimens of this species at the major herbaria in Sarawak and Malaysia including SAR, KEP and the herbarium of Japanese Laboratory in the National Park. Thus it could be a rare species. In Niah National Park, only specimens collected in 1972 and 2007 have been known, and we have no available information at present. Given this situation, we suggest the category of this species as Critically Endangered to the IUCN criteria CR B1a & bi, iii and D. More accurate data on its population size and number of individuals are needed for developing future conservation plan.

Additional specimens examined:— MALAYSIA. Borneo, Sarawak: Miri District, Niah National Park , side trail on left side of main trail, [3°49′26″N; 113°46′57″E], 22 May 2007 (fr.), Siti Eryani et al. S 98493 ( KEP!); Niah, Gn. Subis, Sungei [Sungai] Sekaloh, lower slopes of limestone hill, large limestone boulders, 28 April 1972 (fl.), J.A.R. Anderson S31923 (L, barcode L.2627260, image!)

Discussion:— Mez (1902) classified Ardisia into 14 subgenera, and an additional two subgenera were proposed by Stone (1993: § Scherantha) and Larsen & Hu (1995: § Tetrardisia ) using the characters of habit, leaf morphology, disposition of flowers at inflorescence branch apices (racemes, umbels, corymbs), inflorescence position and floral morphology. Of these, eleven subgenera are present in Malesia with ten in Borneo (see Stone 1982 for a discussion and key to the groups in Malesia; and Julius et al. 2020 for a key to species of § Tetrardisia ); the genus is species-rich in northern Borneo and the subgeneric classification is fundamental to identification of Ardisia in this region. Ardisia pyrotechnica belongs to § Pyrgus because of the terminal inflorescence on a specialized lateral branch below the indeterminate primary axis, which arise directly from the stem (i.e., not axillary) and are leafless except for the bracts subtending the inflorescence; in addition, the lateral branches emerge between two contracted spirally arranged leaves on the stem. The inclusion of this new species within § Pyrgus has been confirmed in the phylogenetic study by the first author [see Julius 2019, identified as Ardisia sp. vel aff. breviramea (sample no. 603)].

Although the pinkish-white flowers and relatively longer sepals of Ardisia pyrotechnica resemble the Bornean species A. breviramea , the two taxa are unlikely to be confused. Ardisia breviramea was formerly assigned into § Acrardisia by Stone (1989: 270) in his checklist to Bornean species, but is a member of § Pyrgus having the terminal inflorescences on specialized lateral branches etc. The new species differs from Ardisia breviramea in several features including the inflorescence size and sepal morphology listed in the diagnosis, but also several other characters: the elliptic leaves with shorter petioles up to 3 cm long (vs. ovate-lanceolate to elliptic or oblanceolate leaves with longer petioles up to 5.5 cm long in A. breviramea ), an acuminate leaf apex (rather than acute to usually acuminate-caudate), arcuate lateral veins joining near the margin (vs. arcuate but not joining), corolla lobes sparsely brown lineate on the upper part (but densely so throughout in A. breviramea ), and only two relatively large foliose bracts below the inflorescence (the inflorescence of A. breviramea is subtended by two large and 1 to 4 small foliose bracts). In addition, A. breviramea is distributed in the north-east region of Borneo, especially around the Tawau region in south-east Sabah.

Figures

FIGURE 1. Ardisia pyrotechnica Julius, Tagane & Utteridge. A Flowering branch showing inflorescence subtended by two large foliose bracts. B Inflorescence, close up. C Mature flower, fully anthesis and floral bract. D Mature flower, partially at anthesis. E Flower dissected to show the stamen arrangement. F Calyx-lobes, showing the adaxial (right) and abaxial surface (left). G Stamen and pistil. H Anther, adaxial (right) and abaxial (left) surface. I Ovary dissected to show the ovules. J Main stem apex showing arrangement of leaves and lateral branch. K The details of venation and glands on the abaxial surface of lamina. Illustration by Mohamad Aidil Nordin.

FIGURE 2. Ardisia pyrotechnica Julius, Tagane & Utteridge. A Habit showing the leaves and flowering branches arrangement on the stem. B Inflorescence subtended two large foliose bracts. C Flower, close-up, adaxial view. D Flower, close-up, abaxial view. Images by Shuichiro Tagane.