Rhodamnia waigeoensis N. Snow, 2012

Snow, Neil, 2012, Five new species of Rhodamnia (Myrtaceae, Myrteae) from New Guinea, PhytoKeys 19, pp. 31-49 : 39-42

Rhodamnia waigeoensis N. Snow sp. nov. Figures 1 6

Closely resembling but differing from Rhodamnia novoguineensis by its thicker and more rigid pedicels, thickly coriaceous leaves, basal acrodromous venation, densely yellowish abaxial laminar indumentum, and solitary flowers.

Type.

Indonesia. Waigeo Island, Go Isthmus, path from Poean Bay to Fofak Bay, 17 Feb 1955, P. van Royen 5556(holotype: A! [bar code no. 00307477]; isotypes: CANB!, K!, L n.v.).

Description.

Trees 5-7 m; girth to 15 cm. Branchlets terete to slightly compressed, the epidermis later becoming fissured; indumentum densely sericeous, mostly yellowish or somewhat ferrugineous but becoming more whitish with age. Leaves opposite, evenly distributed along branchlets, discolorous, glossy above and below, the nacreous sheen below imparted by the dense, tightly appressed greenish-white indumentum. Colleters absent. Petioles 5-6.5 mm long, somewhat flat tened above, densely sericeous (or somewhat tomentose with age), the indumentum yellowish but aging whitish. Leaf blades (3.5-)6.0-10.0 cm long, (1.8-)2.5-3.7 cm wide, narrowly ovate to ovate, surface flat or slightly wavy; base cuneate, apex acuminate and occasionally somewhat falcate, tip acute; venation perfect basal acrodromous; secondary veins numerous but thin, ca. 0.8-2.0 mm apart; marginal nerve prominent, mostly 0.7-0.9 mm from mid-leaf margins; margins flat; adaxial surface sparsely sericeous, midvein flush throughout, oil glands invisible; abaxial surface densely sericeous with greenish-whitish indumentum but this mostly not obscuring venation, midvein raised throughout, oil glands invisible. Inflorescence (limited material) a 3-flowered cyme, terminal, solitary (one per leaf subtending leaf); peduncle ca. 5 mm, stiff, terete in transsection, densely yellowish-orangish sericeous; pedicel to ca. 3 mm long, indumentum as per peduncle. Bracteoles 2, narrowly triangular and stiffly erect, ca. 2 mm long, ca. 0.5 mm wide, sericeous, sometimes persisting into fruit. Hypanthium cupulate, densely sericeous, oil glands absent, texture smooth. Calyx lobes 4, 2.3-3.5 mm long, broadly ovate, sericeous above, densely sericeous below, more or less reflexed in fruit. Petals 4, 5.5-7.0 mm long, width uncertain (material scanty), apparently obovate to broadly obovate, white (based on specimen label), sparsely sericeous above, densely sericeous below. Staminal disk 2.5-3.5 mm wide, densely short-hairy. Ovary apex densely short-hairy. Stamen number uncertain but almost certainly greater than 20, filaments and anthers red (from specimen label); anthers subcylindrical (material scanty), ca. 0.5 mm. Stigma not seen. Locule 1, placentation parietal, placentas 2, ovules numerous. Fruit (reportedly immature) globose-subglobse, up to 8 mm long and 9.5 mm wide, light green when immature, densely sericeous but indumentum thinning with maturity. Seeds irregularly angular, up to 4 mm long (small sample), up to 9 per fruit, crowded; seed coat hard. Embryos not seen.

Phenology.

Flowering February; fruiting in January and February.

Distribution.

Waigeo Island, Indonesia; from ca. 10-150 m elevation in xerophytic, Myrtaceae -dominated vegetation at lower elevations behind and upslope of the village of Waifoi, and from transitional forests dominated by Decaspermum J.R. Forst. & G. Forst. ( Myrtaceae ) or Vatica rassak Blume(= Vatica papuana Schum. & Hollr. [synonym]) ( Dipterocarpaceae ) at the higher elevation (ca. 150 m).

Conservation status.

Data Deficient given the lack of recent information or collections. Rhodamnia waigeoensis is presently known only from two collections. The specimen on the type label indicates that the species was common locally at the time of its collection nearly sixty years ago. A vegetation type similar to that of the type gathering occurs on the island of Rauki, where the species also may occur. While the reported ethnobotanical use of Rhodamnia waigeoensis for cigarette making may lend the species some protection, it also may have encouraged overexploitation.

Vernacular name.

Kikir (in the Malayan language).

Ethnobotany.

The herbarium label indicates that the leaves are used for making cigarettes.

Comments.

Rhodamnia waigeoensis belongs in the “pearly” group of species given its nacreous indumentum ( Snow 2007). Scott (1979) included the type gathering of Rhodamnia waigeoensis in Rhodamnia novoguineensis A.J. Scott and the paratype gathering in Rhodamnia pachyloba A.J. Scott.

Rhodamnia waigeoensis differs from Rhodamnia novoguineensis by its thickly coriaceous leaves (vs. thinly coriaceous in Rhodamnia novoguineensis ), consistently basal acrodromous leaf venation (vs. even or uneven suprabasal acrodromous in Rhodamnia novoguineensis ), dense abaxial laminar indumentum with yellowish trichomes (vs. relatively sparse and whitish in Rhodamnia novoguineensis ), solitary flowers (vs. triads or few-flowered racemes in Rhodamnia novoguineensis ), thicker (0.5-0.7 mm wide) and rigid pedicels (vs. ca. 0.3 mm thick and flaccid in Rhodamnia novoguineensis ).

Waigeo Island is part of the Raja Ampat Islands of Indonesian New Guinea. The region harbors unusual vegetation assemblages (van Royen 1960), has high rates of endemism ( Supriatna 1999), and was the subject of relatively recent rapid-assessment surveys ( Takeuchi 2003a). Van Royen (1960: 54-56) summarized the vegetation on portions of Waigeo Island using six broad categories. One of these, xerophytic vegetation, is described as having three variants, one being dominated by Myrtaceae .

The label of the type specimen refers directly to the xerophytic vegetation located behind the small village of Waifoi on the east bank of Majalibit Bay. Takeuchi (2003a,b) reported that the Waigeo ultrabasic vegetation resembles the pioneer communities on the ultrabasics at the Kamilai Wildlife Management Area (KWMA) in the Bowutu Mountains (Morobe Province, Papua New Gueina). Communities at KWMA can be topographically unstable due to landslides, but in general appearance and composition are similar to those on Waigeo. However, Takeuchi (2003b) believes the vegetation on the Waigeo ultrabasics is primarily caused by fire succession.

A xerophytic vegetation similar to that occuring on the hills upslope of Waifoi, the village near the type collection, was encountered elsewhere by van Royen (1960: 39, 41) in the Kambelay Hills and the Go Isthmus of Waigeo Island. This general type of xerophytic vegetation is said to recur on Rauki Island, which lies northwest of Kabaré Bay, where it occurs at the higher elevations (probably less than ca. 40 m, but reported by van Royen [p. 45] as 25 m) along the southern end of the island (van Royen 1960: 44) at ca. 0°52'S, 130°56'E (coordinates based on Google Earth ™ [accessed 2 June 2009]). (Rauki Island has been known previously as Rawak, Rawah or Lawak [van Royen 1960: 43]). The substrates underlying the xerophytic vegetation of Rauki include ultrabasic outcrops among the more prevalent limestone (van Royen 1960: 45).

Van Royen (1960: 32) described the soils underlying the xerophytic vegetation on Waigeo as "sandy brown clays with much limestone". The relatively open vegetation on the slopes was indicated as being spare of trees but conspicuous in its presence of shrubby Myrtaceae . Noted specifically for Myrtaceae (van Royen 1960: 32, 55, 59) were Baeckia frutescens L., Myrtella beccarii F. Muell. and Decaspermum rubrum (Blume) Baill. (as Decaspermum fruticosum J. R. Forst. & G. Forst.var. rubrum, a nomenclatural change that was apparently never validly published [ Scott 1985; Govaerts et al. 2008]), and " Rhodamnia trinervia Reinw. ex Blume ". However, the collection number (5556) that van Royen (1960: 59) cited for Rhodamnia trinervia represents the holotype of Rhodamnia waigeoensis , and Rhodamnia trinervia is now considered to be a synonym of Rhodamnia rubescens (Benth.) Miq. (e.g., TPL 2012).

Specimen examined.

West Papua (Papua Barat; as Radjah Ampat on label), Waigeo Island, Waifoi on E bank of Majalibit [= Mayalibit] Bay, 18 Jan 1955, P. van Royen 5227 (L).

Figures

Figure 1. Island of New Guinea, showing localities of new species. Triangle (▲) = Rhodamnia asekiensis; Square (■) = Rhodamnia daymanensis; Diamond (◆) = Rhodamnia makumak (at bottom of line); Closed circle (⚫) = Rhodamnia toratot (at top of line); Inverted triangle (▼) = Rhodamnia waigeoensis (upper left, at bottom of line); Open circles (⚪) = Rhodamnia sharpeana (left end of line [upper] and bottom of line [lower, on truncated eastern half of Tagula Island]).

Figure 6. Rhodamnia waigeoensis N. Snow. Photo of the the holotype at A (P. van Royen 5556)