Pinanga leonardcoi Adorador & Fernando, 2022

Adorador, Jiro T. & Fernando, Edwino S., 2022, Pinanga leonardcoi (Arecaceae), a new species from Mt. Cagua in northeast Luzon, Philippines, Phytotaxa 536 (2), pp. 183-189 : 185-188

Pinanga leonardcoi Adorador & Fernando , sp. nov.

Type:— PHILIPPINES, Cagayan Province: Luzon Island, Gonzaga , Barangay Santa Clara , Mt. Cagua , ± 800 m elev., August 22, 2021, J.T. Adorador 201 (holotype PNH!; isotypes CAHUP!, LBC!)

Diagnosis: — P. leonardcoi is closely related to members of the Urosperma group, namely, P. glaucifolia , P. samarana , and P. urosperma but differs by the combination of the following characters: clustered stems with stoloniferous offshoots, very few rachillae (2–3) with spirally arranged fruits, and fruiting perianth with imbricate calyx lobes.

Clustering moderately slender undergrowth palm, to 4 m tall. Stem to 3.5‒4 cm diam., internodes about 7 cm apart. Crownshaft elongate c. 40 cm long, cylindrical, slightly swollen. Leaves to 6 in crown, sheath 25‒35 × 4‒4.5 cm, yellowish green, glaucescent, ligules narrowly triangular, inconspicuous, leaf (including petiole) without sheath 123‒191 cm long, petiole 25‒44 × 1.2‒1.5 cm, shallowly channeled adaxially, convex abaxially sparsely covered with brown scales, rachis angular, 69‒153 × 1 cm, bifacial adaxially and rounded abaxially with indumentums as petiole. Leaflets 8‒13 per side of the rachis, coriaceous, ± straight, generally multi-costulate except occasionally for basal leaflets, ± regularly arranged, 4.3‒6.5 cm apart, the apex long acuminate to subfalcate, glossy green adaxially drying grayish, much paler green and glabrescent abaxially drying brownish, with midfixed ramenta along the midrib to 4 mm long; basal leaflets 1‒4 costulate, 38‒59 × 21.5‒ 5.5 cm, middle leaflets 2‒3-costulate, 52.5‒79 × 3.5‒6, apical leaflets 4‒11 costulate, 26‒41 × 2‒11.5 cm, joined to 16 cm at the base along the rachis. Infructescence 16‒29 cm long, the axes greenish yellow, prophyll unknown, peduncle 3.7‒4 × 1.4 cm, with just 2‒3 ultimately pendulous rachillae, 13‒19.5 × 0.7 cm, rachillae bracts very shallow gibbous; flowers spirally arranged throughout the rachillae. Staminate and pistillate flowers not known. Fruit broad ovoid at maturity, up to 2‒3 × 1.5‒2.6 cm, with short conical apex, spirally arranged, ripening greenish red, up to 37 fruits along rachis, fruiting perianth 2.5‒3 × 6‒7 mm, with broad imbricate calyx lobes, not contracted at the mouth. Seed ovoid, to 2.1 × 1.7 cm, rounded apically, obliquely concave below, endosperm ruminate, embryo short conical to 3 mm long. ( Figures 2 & 3 )

DISTRIBUTION AND HABITAT: —There are just about eight isolated individuals encountered in the general area of occurrence. These accounted clusters are all situated inside the caldera of Mt. Cagua where it prefers welldrained gentle slopes or valleys.

LOCAL NAME:— None recorded. With most common names of Philippine Pinanga being referred as or derived from ‘ abiki ’, we hereby formalize this new species to be called as ‘ Leonard’s abiki’.

OTHER SPECIMENS EXAMINED:— PHILIPPINES, Cagayan Province: Luzon Island, Gonzaga, Barangay Santa Clara , Mt. Cagua , ± 800 m elev., August 22, 2021, J.T. Adorador 202 (LBC!; K!, PNH!), J.T. Adorador 203 (LBC!: PNH); [possibly from Barangay Magrafil], 1990–1995, J.P. Bautista 902 [PUH017387] PUH !).

CONSERVATION STATUS:— Using the online GeoCAT conservation assessment tool ( Bachman et al 2011), the new species’ AOO (area of occupancy) is calculated at 4 km 2 which is within the threshold for the Critically Endangered category ( IUCN 2012). Following IUCN (2012) and IUCN Standards and Petitions Subcommittee (2019), we regard this species as Critically Endangered [CR B2 a b(v), D]. The new species is only recorded within the forested crater of Mt. Cagua with just eight surveyed mature individuals whose extinction is highly probable in the advent of a major eruption.

ETYMOLOGY:— This slender palm is named after the late Leonardo L. Co (also fondly called as just ‘Leonard’) of the Institute of Biology, College of Sciences, University of the Philippines Diliman in honor of his selfless devotion to the advancement of understanding, exploration, and conservation of Philippine native plants. Leonard Co was lead botanist of the team that collected the first herbarium specimen of this new Pinanga from Mt. Cagua.

NOTES:— Pinanga leonardcoi shares the fruiting perianth of imbricate calyx lobes with the more southern representatives, P. glaucifolia (of Bicol peninsula) and P. samarana (of Samar and Dinagat Islands) but these two species significantly differ in their solitary habit, having different abaxial leaf surface (glaucescent in P. glaucifolia and microlepidote in P. samarana vs. glabrescent in P. leonardcoi ), greater number of rachillae (6–10 in P. glaucifolia and 10–21 in P. samarana vs just 2–3 in P. leonardcoi ), and distichously arranged [sometimes seemingly becoming spiral in distal parts of rachillae due to mutual pressure upon fruit maturation] relatively smaller fruits, up to 2 cm × 1.8 cm (vs spirally arranged larger fruits, up to 3 × 2.6 in P. leonardcoi ). Meanwhile, the geographically sympatric P. urosperma (of northern to northeastern Luzon and immediate islands) differs in its solitary habit, the infructescence with 4–5 rachillae with distichously arranged fruits, fruit apex being narrow conical (vs. short conical in P. leonardcoi ) and fruiting perianth with valvate calyx lobes.

Among the Philippine congeners, only P. sobolifera Fernando (1994: 782) of the Philippinensis group, likewise possess the combination of stoloniferous basal shoots and spirally-arranged fruits but P. leonardcoi differs in its more robust stems (3.5–4 cm vs to 2.5 cm in P. sobolifera ), fewer rachillae (vs. 8–11 in P. sobolifera ), and much larger fruits, averaging 2.4 cm × 1.8 cm (vs 1.2 × 0.8 cm in P. sobolifera ). Meanwhile, the other locally sympatric but more widely occurring congeners, viz. P. philippinensis Beccari (1889: 180) , P. maculata Porte ex Lemaire (1863 : pl. 361) and P. insignis Beccari (1907: 223) , cannot be confused with P. leonardcoi as these three taxa belong to separate groups of Philippine Pinanga ( Adorador et al. 2020) .

It is curious that P. leonardcoi has only been collected once before as compared to the other generally sympatric Pinanga which rather indicates its rarity in this sub-biogeographic region. Apparently, this palm has successfully established within Mt. Cagua’s caldera—a geologically recent habitat with the last known eruption in 1860 and strong solfataric activity in 1907 ( Smithsonian Institution 2013). Likewise, the caldera’s average elevation of 821 m approximates the general elevational species turn-over for palms at around 1,000 (± 200) m elev. (authors’ personal observations). Thus, its preference to this unique environment and the paucity of additional distribution records altogether indicates that P. leonardcoi is a very narrow endemic palm or could even be a neo-endemic species.

Figures

FIGURE 2. Pinanga leonardcoi Adorador & Fernando, clustering habit (A), leaves with 2–3-costulate segments (B), stem with infructescences (C) in different phases of development (D–F), Close-up of fruits showing imbricate fruiting perianth (G), longitudinally dissected fruits showing ruminate endosperm and basal embryo (H), basal off-shoot with a stoloniferous stem (I). All from the holotype, J.T. Adorador 201 (PNH) except F from J.P. Bautista 902 (PUH). Scale bar: B—40 cm, C—15 cm, D & E—15 cm, G—40 cm, I—8 cm. Photos by J.T. Adorador.

FIGURE 3. Pinanga leonardcoi Adorador & Fernando, clustering habit (A), middle leaflets with 3-costulate segments (B), apical leaflets (C), immature fruit showing imbricate fruiting perianth (D), infructescence showing spirally arranged fruits (E), longitudinally dissected fruits showing ruminate endosperm and basal embryo (F), seed with adherent portions of the pericarp (G), and basal of-shoot with a stoloniferous stem (H). B–C from J.T. Adorador 202, D–H from the holotype, J.T. Adorador 201.Scale bar: B & C—6 cm, D—1 cm, E—7.5 cm, F—2 cm, G—1.8 cm, H—8 cm. Drawn by J.T. Adorador