Pinanga samarana Beccari, 1919

Adorador, Jiro T., Meneses, Zhereeleen D. & Fernando, Edwino S., 2020, Pinanga gruezoi (Arecaceae), a new slender clustering palm from the Philippines with notes on an amended description of P. samarana, Phytotaxa 429 (2), pp. 120-134 : 128-131

Pinanga samarana Beccari

Type:— PHILIPPINES, Samar Island, Mt. Cauayan , March-April 1914, Ramos B. S. 17535 (holotype FI! [ FI013968 ]; isotypes BM! [ BM001040830 ], K! [ K000207955 ], P! [ P01799175 ], US! [ US 0087685])

Solitary slender to moderately slender undergrowth palm, to 4 m tall. Stem 1.1‒5 cm diam., internodes typically 4 cm apart. Crownshaft elongate, cylindrical, slightly swollen. Leaves 5‒6 in crown, sheath 26‒35.3(‒42) × 2.8‒3.8(‒5) cm, yellowish green, glaucous, ligules inconspicuous to 1‒2 cm long, narrowly triangular. Leaf without sheath but including typically to c. 160 cm long, petiole c. to 40‒50 cm long, shallowly channelled adaxially, convex abaxially sparsely covered with thin glaucescence as sheath, rachis angular, typically c. 120 × (0.3‒) 0.6‒1.2 cm, bifacial adaxially and rounded abaxially with thin glaucescence similar to that of the petiole or glabrous. Leaflets 10‒27 per side of the rachis, coriaceous, subglabrescent, straight or ensiform to indistinctly subfalcate, variably 1‒7-costulate, ± regularly arranged, 3.3‒6.3(‒10.9) cm apart at the middle portion of rachis, the apex long acuminate, glossy green adaxially drying grayish, much paler green abaxially drying reddish-brown (when preserved in alcohol) and conspicuously microlepidote, furnished with midfixed ramenta along the midrib to 3 mm long; basal leaflets 1‒2(‒4)-costulate, 21.4‒42.3(‒67.8) × 0.6‒2.5(‒6.7) cm, middle leaflets 1‒4-costulate, 22.5‒48.9(‒64.4) × 0.8‒2.8(‒7.0), apical leaflets (1‒)4‒9-costulate, 17.9‒32.2(‒45.5) × 0.9‒2.7(‒6.8) cm, joined up to 7 cm at the base along the rachis. Inflorescence c. 11‒22(‒41) cm long, prophyll 15 × 5 cm, peduncle 1.0‒1.7(‒2.5) cm, rachis 4.3‒7.9(‒16.5) cm long, rachillae bracts gibbous, 1 mm high, rachillae (10‒)14‒21, subdistichously- to spirally-arranged, (5.5‒) 12.5‒22.5 cm long; flowers distichously arranged. Staminate flowers c. 1.2 × 0.5 cm, calyx 1 mm high, 3-lobed, joined at the base, petals valvate, 1‒1.2 × 0.3‒0.5 cm, broad to narrow oblique triangular, apex conspicuously apiculate, stamens 14‒15(‒19), filaments 0.5 mm long, anther basifixed, 1 mm long. Pistillate flowers 1.5 × 2 mm, with broadly ovate imbricate calyx and corolla lobes, margins ± fimbriate. Fruit ovoid-ellipsoid to obovoid or globose, 1.2‒1.7 × 0.6‒1 cm, apex shortly conical to areolate, distichously arranged throughout rachillae or only at proximal part then spirally arranged distally, developing from green‒cream‒orange‒red‒reddish black, 12‒20(‒28) fruits per side of the rachis, set to 2‒8 mm apart., fruiting perianth 1.5‒3 × 3‒6 mm, somewhat broadened at the mouth. Seed ovoid‒ellipsoid to obovoid or globose, 0.9‒1 × 0.8 cm, rounded apically, obliquely concave below. Eophyll bifid. ( Figure 4 )

Distribution and Habitat: —This palm was thought to be restricted to Samar Island but is now known to occur on Dinagat Island as a well ( Figure 5 ).

Local Name:— The Waray (Samar Island local inhabitants) guides generally referred to this palm as tagibunga while the Mamanwa tribe (migrant indigenous people from Mindanao Island) occupying Km. 16, Tinabanan, Marabut, Samar call this palm salanguisog. It is noteworthy, that the Manobo tribe (indigenous people from northeastern Mindanao) also use the latter vernacular name for P. urdanetensis (as per notes of Elmer in Beccari 1919b).

Other specimens examined:— PHILIPPINES. Samar Island: Samar Province, Paranas, Barangay Tenani , 07 July 2015, J. T. Adorador 003 ( LBC! PNH! K!) ; 18 July 2016, J. T. Adorador 011 ( LBC!, PNH!) ; 29 July 2015, J. T. Adorador 032 ( LBC!) ; Barangay San Isidro , 28 February 2016, J. T. Adorador 027 ( LBC!) ; without exact locality, 13-18 March 2016, D. N. Tandang & E. R. Tadiosa PNH 256475 ( PNH!), Hinabangan, Barangay Cansolabao, Sitio Arizona , 11 March 2015, J. T. Adorador 018 & T. Rambacod ( LBC!) ; 19 July 2015, J. T. Adorador 006 ( LBC!) ; 24 July 2015, J. T. Adorador 025 ( LBC!) ; Barangay Bagacay, Mt. Concord , c. 200 m elev., 21 April 1948, Sulit & Conese 2716 ( PNH!) ; Marabut, Barangay Tinabanan, Km 16, 19 February 2016, J. T. Adorador 082 ( LBC!) ; Basey, Mt. Sohoton , March–April 1970, H. G. Gutierrez et al. 544 ( PNH!) ; Eastern Samar Province, Balangiga, Guinmaayuhan , May 1971, D. A. Madulid et al. 1370 ( PNH!) ; Salcedo, Barangay Carapadapan, J. T. Adorador 090 ( LBC!), 55 m elev., 15 May 2009, E. S. Fernando 2155 ( LBC!). Dinagat Island: Dinagat Province, Loreto, Balitbiton forest , 179 m elev., 2016, E. P. Lillo LDLCP3 SP8 ( LBC!), Libjo, Paragua forest , 188 m elev., 2016, E. P. Lillo LDLP1 SP61 ( LBC!) .

Conservation status:— The area of occupancy (AOO) of Pinanga samarana is estimated at 52 km 2, thus we regard this species as Endangered [EN B2 b(ii, iii) c(iii)]. Preliminary palm surveys conducted February 2016 in thirty-six 20 m × 20 m nested plots established across different forest types at SINP, revealed that Pinanga samarana occurred in 21 out of 36 plots and that it was the most abundant, erect palm species. We recorded 609 palm individuals (164 mature, 127 saplings, and 318 seedlings) ( Adorador 2016 unpublished data). Despite high abundance in some areas, this species is threatened by fluctuating population sizes and continuing habitat degradation such as land-use conversion and/or illegal logging (on Samar Island) as well as mining activities planned in the area especially on Dinagat Island.

Etymology:— This palm is named after the island of its type locality, Samar Island, Philippines.

Notes:— The description of the holotype (Ramos B.S. 17535) from fragmentary material (few leaflets and immature infructescence) makes it difficult to delimit this taxon in situ. But several site visits, herbarium studies, and careful observations across the different forest formations permitted sound generalizations on the actual extent of its morphological variations.

Pinanga samarana , as characterized by its solitary habit, moderately slender stem (2–6 cm diam.), non-mottled typically 1–3-costulate middle leaflets, and relatively few rachillae (ave. 14) belong to the Urosperma group which includes P. glaucifolia Fernando (1994: 776) and P.urosperma Beccari (1909: 341) . It also share superficial resemblance with P. urdanetensis Beccari (1919b: 3008) which undoubtedly belongs to the widespread and highly polymorphic P. philippinensis Beccari (1889: 180) complex of the Philippinensis group [unpublished data] ( Table 2). Broadly cicumscribed, P. samarana is a medium-sized solitary palm with glaucescent leaf sheath having entire margins, typically 2-costulate leaflets (sometimes variably 1–3-costulate) that are drying reddish-brown with microlepidote underneath, inflorescence with several (up to 21) subdistichous to spirally arranged rachillae, and relatively large (to 1.8 × 1 cm) distichously-set (or becoming spiral distally) ovoid-ellipsoidal to obovoid fruits. Particularly, P. samarana is most similar to P. glaucifolia but the latter is different in its leaflets being abaxially glaucous without distinct microlepidote, fewer number of rachillae (6–10), and much larger ovoid-globose or sphaeroidal (2 × 1.8 cm). On the other hand, P. urosperma is decidedly different from P. samarana in its fewer rachillae number (4–5 vs. 10–21 in P. samarana ) and larger bullet-shaped fruits (up to 3.2 × 1.8 cm).Meanwhile, as stated in the protologue ( Beccari 1919b), P. urdanetensis only differs from P. samarana by its leaflets being abaxially grayish-brown when dried without conspicuous microlepidote and apparently smaller fruits (though only then known from immature fruits). But when P. samarana is altogether compared to the P. philippinensis complex, the latter significantly deviates in its habitat preference being found in lower to upper montane forests or 600–more than 2,000 m elev., leaf sheath margins readily disintegrating into fibers and its surface covered with rust-brown to purplish lepidote, relatively smaller fruits (up to 1.4 × 0.8 cm) and the fruit pericarp typically turn creamish-pink just before maturation (orange in P. samarana ).

We documented several leaflet costulation types among different populations found on various forests types which could be affected by wind flow and the amount of light penetrating though the canopy ( Svenning 2001). The leaflets of palms thriving over limestone are the most unusual being linear 1-costulate ( Figure 4 A ), while those inhabiting lowland forests typically are subfalcate 2-costulate ( Figure 4 B ) and those from forest over ultramafic sites are linear 3-costulate ( Figure 4 C ). The rachillae architecture ranges between drooping to slightly arching ( Figure 4 D ) and to spreading and reflexed ( Figure 4 E ). Meanwhile, fruit arrangement along rachillae could be well-spaced and distichous throughout or the dense-clustered and spiral in distal portions. Fruit shapes vary from ovoid-ellipsoid, obovoid, short ovoid to globose ( Figure 4 F–I ). As observed in-situ, both rachillae morphology and fruit arrangement are possibly shaped by constrained expansion during early development within the prophyll and mechanical displacement of fruits upon maturity due to mutual pressure. The pigment of the fruit also seemed to be affected by light availability and edaphic conditions. Pericarp exhibits more orange colouration before maturity when developing under shade and growing on soils on top of limestone while it is recorded to be just lightly orange when more exposed to light and thriving on ultramafic soils. Likewise, individuals exhibiting combinations of these leaf and fruit characters were also encountered hence its broad circumscription.

Below is a conspectus of tentative functional groups of Philippine Pinanga based on analyses of literature (heavily modified from Beccari (1919a) and herbarium studies. Among the derived groups, only the Maculata group has been treated before ( Fernando et al. 1988) while the others are subject to future taxonomic studies.

Figures

FIGURE 4. Pinanga samarana Beccari from Samar Island. Leaflet variations: linear 1-costulate (A), subfalcate 2-costulate (B), and 3- costulate (C). Infructescence and rachillae architecture: drooping (D) or reflexed (E). Fruit arrangement along rachillae and fruit forms: the typical distichously-arranged ovoid-ellipsoid (F) or obovoid fruits (G), or distal portions of rachillae turning spiral with short-ovoid (H) or globose (I) fruits. Localities: Barangay Tenani, Paranas, Samar (A,E,G = from Adorador 003), Sitio Arizona, Barangay Cansolabao, Hinabangan, Samar (D,F = Adorador 025, I = Adorador 018 & Rambacod), Barangay San Isidro, Paranas, Samar (H = Adorador 027). Scale bar: A = 30 cm, B = 40 cm, C = 60 cm, D & E = 15 cm, F = 10 cm, G‒I = 2 cm. Photos A‒I (Jiro T. Adorador).

FIGURE 5. The distribution map of Pinanga samarana Beccari and closely related species based on herbarium records. The gray-shaded area approximates the c. 150 meters below sea level bathymetry line which shows several Pleistocene Aggregated Island Complexes (PAIC) (Heaney 1986).