Medinilla malabrigoi Z.D.Meneses, Adorador & Quakenbush, 2021

Adorador, Jiro T., Meneses-Adorador, Zhereeleen D. & Quakenbush, J. Peter, 2021, Medinilla malabrigoi (Melastomataceae), a new species from forests over limestone in Samar Island, Philippines, Phytotaxa 483 (2), pp. 95-105 : 98-103

Medinilla malabrigoi Z.D.Meneses, Adorador & Quakenbush , sp. nov.

Type: Philippines, Samar Island , Samar Province, Paranas, Barangay San Isidro , ca. 300 m elev., 13 July 2017, Adorador & Meneses 010 (holotype PNH; isotypes CAHUP, LBC)

Diagnosis:— M. malabrigoi is most similar to M. polillensis s.l. and M. peltata , but is different in its strictly terrestrial erect habit (variable in M. polillensis s.l. and scandent in M. peltata ); leaves that are sessile, sometimes ternate, narrow-lanceolate, 3-plinerved, and with cordate bases (petiolate, strictly opposite, broad-lanceolate to elliptic oblong, 5-7-plinerved, with acute to subpeltate base in M. polillensis s.l.; and ovate with distinctly peltate base in M. peltata ); umbellate inflorescences (cymose in M. polillensis s.l.); and flared, reflexed calyxes even at anthesis (truncate-obconical in M. polillensis s.l. and short truncate-denticulate in M. peltata ).

Lithophytic, erect shrub up to 2 m tall. Stems 2 cm diam. near the base, branches somewhat squarrose, up to 1 cm in diam., internodes 1.9–3.5 cm long; young stems 0.4 cm diam., squarrose or ridged, glabrous, bark generally smooth, becoming striate when old. Leaves sessile, opposite, ± decussate in terminal branchlets, rarely ternate, narrowly lanceolate, 8.5–18.5 × 1.2–3.6 cm, coriaceous, glossy dark green adaxially, paler abaxially, with reddish tinge when young, base subcordate to cordate, apex bluntly acute; 3-plinerved, the pair of acrodromous veins diverging from the leaf base and visible on both surfaces in fresh and dried state; transverse veins absent; margins smooth, revolute at the edges. Inflorescences cauline, arising from leafless nodes near the base of the stem, lateral to slightly pendulous, borne on short rounded tubercules, usually solitary or sometimes two to three, umbellate, typically 2–7-flowered, (rarely in 2 whorls), 3.5–6.5 cm long, the axes green to bronze at anthesis; peduncles stout, 1.1–2.6 cm long, tapered or enlarged towards the distal end, bracts and bracteoles minute; pedicel 13–20 mm long, continuous with the hypanthium; hypanthia campanulate, 8−10 × 8−10 mm, calyxes 1.1–4 mm long, flared and reflexed at anthesis, becoming spreadingly-stiffened at fruit. Flower buds ± bluntly pointed at the tips, flowers 4(–5)-merous, petals imbricate, 14–19 × 9–17 mm, obliqueoblong to obovate, often reflexed, translucent pink; stamens 8(–10), equal, usually positioned above the style, anthers linear-lanceolate, 8−10 mm long, curved, purple, with a yellow dorsal spur of 1.2–2 mm long on the connective and a pair of partly joined, stout, ventral appendages at the base of the anther sac 0.8 mm long; filament 10 mm long, pale white; style terete, 18 mm long, pale white. Fruit ovoid-ellipsoid berries, 12−15 × 6.5−8 mm (including calyx), greenish brown when young, dark purple when ripe; the axes concolorous with fruit, distal ends swollen at maturity. Seeds numerous, embedded in pulpy tissue, ± ovoid-triangular, to 1 × 1 mm, chestnut brown. (See Figures 1–3 .)

Habitat and Ecology:— M. malabrigoi is a lithophytic species occurring on forests over limestone formation at ca. 380 m elev. in Paranas, Samar Island, Philippines. The rhizospheric soil, whenever present, is sandy loam with high levels of calcium (7,152 ppm), iron (202,911 ppm), manganese (2,613 ppm), and nickel (476 ppm); but with trace amounts of phosphorus and potassium (unpublished data). The canopy of the surrounding vegetation is approximately 5–20 m high, which is formed by predominantly spindly (ca. 5–10 cm diam.) tree species of Tristaniopsis (Myrtaceae) , Buchanania (Anacardiaceae) , Diospyros (Ebenaceae) , Drypetes (Putranjivaceae) , Lunasia (Rutaceae) , Shorea (Dipterocarpaceae) , Psychotria (Rubiaceae) , Radermarchera ( Bignoniaceae ), Syzygium (Myrtaceae) , Terminalia (Combretacee) , and Xylosma (Salicaceae) , among others. The shrub layer is comprised of various species of Ixora (Rubiaceae) , Memecylon (Melastomataceae) , Osmoxylon (Araliaceae) , Pandanus (Pandanaceae) , and Tabernaemontana (Apocynaceae) ; while the herbaceous component includes Alocasia (Araceae) , Begonia (Begoniaceae) , Elatostemma (Urticaceae) , Kalanchoe (Crassulaceae) , and various species of ferns and orchids. Several species of Medinilla were also documented in the same localities, namely M. cephalophora Merrill (1908: 250) , M. myrtiformis ( Naudin 1851: 305) Triana (1871: 86) , M. peltata , M. setigera , M. teysmannii Miquel (1864: 217) and several forms of M. pollilensis s.l.

Distribution:— Philippines, Samar Island, Samar Province, Municipality of Paranas. Endemic. This new species is only known atop several forests over limestone in the municipality of Paranas, Samar, which is within Samar Island Natural Park (SINP). (See Figure 4 .)

Etymology:— This new species of Medinilla is named in honor of the Filipino taxonomist and conservation advocate, Professor Pastor L. Malabrigo Jr. of the Department of Forest Biological Sciences, College of Forestry and Natural Resources, University of the Philippines at Los Baños, in acknowledgement of his efforts in Philippine flora conservation.

Other Specimens Examined:— Philippines, Samar Island , Samar Province, Paranas, Baranagy San Tenani , ca. 350 m elev., 18 December 2015, Adorador & Meneses 005 ( CAHUP), 006 ( LBC) .

Conservation Status:— Endangered [EN B1 b(ii) c(iv)]. Medinilla malabrigoi is thus far documented near the summit of two limestone formations in Paranas, Samar. The observed distribution is sporadic, with a corresponding small population size of mature plants. Using GeoCAT (geocat.kew.org), the new species’ estimated area of occupancy is calculated at just eight (8) km 2, but its topographical preference atop limestone formations suggests a more widespread occurrence across the forested rolling hills (ave. 400 m elev.) in the central eastern part of Samar ( Travaglia et al. 1978). This inference projects the extent of occurrence at ca. less than 200 km 2, which is still within the threshold for Endangered category following IUCN (2012) and the Guidelines for Using the IUCN Red List Categories and Criteria ( IUCN Standards and Petitions Subcommittee 2017). Remoteness and relatively inaccessible terrain may provide protection in the near future from anthropogenic alterations of habitat, but very limited range makes the species vulnerable to even localized changes in climate, e.g. prolonged drought.

Notes:— Distribution-wise ( Fig. 4 ), M. polillensis s.l. reaches furthest north and is present on the Pleistocene aggregate island complexes (see Heaney 1986) of Greater Luzon, Greater Negros-Panay, and Greater Mindanao. M. peltata reaches furthest south and primarily exists on Greater Mindanao. M. malabrigoi is in the middle, at the northern end of Greater Mindanao, where all three taxa overlap. These three taxa were even observed to grow sympatrically in one locality. Previously, the only member of the M. polillensis alliance known from Samar was M. peltata ; but the group is well represented. Along with the newly described species, recent collections by ZDMA and JTA suggest the presence of still other distinctive forms of or related to M. polillensis s.l. However, the variability of stem, leaf, habit, and floral characters are too poorly known at present to warrant taxonomic adjustments that risk adding to the complexity of an already complex taxon.

Figures

FIGURE 1. Habitat, habit, and leaves of Medinilla malabrigoi—A. forest over limestone (ca. 380 m elev.) in Tenani, Paranas, Samar, B. erect habit with (rarely) 3-whorled leaves, C. narrow-lanceolate, 3-nerved leaves with cordate (to almost perfoliate) bases, adaxial surface, D. Abaxial leaf surfaces. B & D from the holotype (Adorador & Meneses 010). Scale bar: B = 40 cm, C & D = 10 cm. Photos: J.T. Adorador

FIGURE 2. Medinilla malabrigoi—A. cauliflorous umbellate inflorescence borne at the base of the stem, B. close-up of the flowers showing translucent petals, C. flowers past anthesis showing reflexed hypanthium lobes, and D. immature fruits.A & B from the holotype (Adorador & Meneses 010). Scale bar: A = 10 cm, B–D = 2 cm. Photos:A–C, J.T. Adorador; D, Z.D. Meneses.

FIGURE 3. Medinilla malabrigoi—A.apical portion of the stem showing the opposite phyllotaxy and leaf form, B. cauliflorous, umbellate inflorescence borne on a squarrose branch, C. close-up of a flower, D. infructescence in two whorls (rarely observed) with fruits crowned with reflexed calyx, and E. longitudinal sections of the fuit.A–C from the holotype (Adorador & Meneses 010), D & E from Adorador & Meneses 005. Scale bar: A = 6 cm, B = 5 cm, C = 2 cm, D = 3.5 cm, E = 1.5 cm. Drawn by J.T. Adorador

FIGURE 4. The distribution map of the Medinilla polillensis alliance (including M. malabrigoi, M. peltata, and M. polillensis s.l.) based on literature, herbarium, and photographic records.The gray-shaded area approximates the ca. 150 meters below sea level bathymetry line which shows several Pleistocene aggregated island complexes (Heaney 1986).