Rhodamnia daymanensis N. Snow, 2012

Snow, Neil, 2012, Five new species of Rhodamnia (Myrtaceae, Myrteae) from New Guinea, PhytoKeys 19, pp. 31-49 : 34-35

Rhodamnia daymanensis N. Snow sp. nov. Figures 1 3

Resembling Rhodamnia lancifolia but differing by its more deeply sulcate petiole, broader leaves, and shorter yellowish indumentum on the abaxial laminar surface.

Type.

PapUa New Guinea. Milne Bay District, north slopes of Mt. Dayman, Maneau Range, 2250 m, ca. 9°47'S, 149°18'E, 2 Jun 1953, L. J. Brass 22718 (holotype: A!; isotype: L!)

Description.

Trees 15-18 m. Indumentum (branchlets, inflorescence axis, flowers) densely appressed sericeous or sericeous-villous (trichomes yellowish). Branchlets terete to compressed, brown (dried), epidermis smooth, becoming flakey or scaly, sericeous-villous. Leaves opposite, evenly distributed along branchlets, strongly discolorous, internodes 1-3 cm long; venation perfect basal acrodromous, secondary and tertiary veins visible above and below; intramarginal vein closely paralleling leaf margin, 0.5-0.7 mm from margin at midpoint of blade. Colleters absent. Petioles 5-9 mm long, slightly sulcate throughout. Leaf blades 3.8-7.0 cm long, (1.1-)1.5-3.0(-3.5) cm wide, elliptic (rarely broadly elliptic), base cuneate, apex narrowly acuminate, tip acute and somewhat falcate; adaxial surface matte, sericeous but becoming glabrescent, midvein slightly sulcate in proximal half but more or less flush distally; abaxial surface densely sericeous between the secondary and tertiary veins, midvein projecting throughout, oil glands (if present) entirely obscured by indumentum. Inflorescence axillary, flowers solitary (=monads) or in 3-flowered cymes (=botryoids), solitary to paired or fascicled in axils, pedicels of monads up to 1-5 mm long, rigid and ascending. Bracteoles 1.5-3.0 mm long, less than 0.5 mm wide at base, linear, mostly erect or ascending, mostly persistent in flower. Hypanthium 2.5-3.3 mm long, ca. 2.5 mm wide at base of calyx lobes, cupulate, densely hairy. Caly x lobes 2.7-3.0 mm long, broadly obtuse, glabrescent adaxially, densely sericeous abaxially. Petals 5.5-7.0 mm long, 3.0-3.5 mm wide, ovate to narrowly ovate, whitish, mostly glabrous adaxially, densely sericeous abaxially, oil glands common. Stamens 65-75, multiseriate; staminal disk short-hairy; filaments 2-3 mm long; anther sacs 0.3-0.5 mm long, globose to subcylindrical, sub-basifixed or basifixed, crowned by a single large apical gland. Style ca. 4.5 mm long, glabrous; stigma narrow to slightly capitate, prominently papillose. Ovary and locule 1, placentas 2, linear, ovules disposed in regular rows.

Phenology.

Flowering in June; fruiting interval unknown.

Distribution.

Papua New Guinea, Milne Bay Province, north slopes of Mt. Dayman in the Maneau Range; mossy forest of ridge crests over metamorphic rocks (see Davies 1980; Daczko et al. 2009) at ca. 2250 meters.

Conservation status.

Data Deficient. The collection label indicates the species was common (at least locally) at the time of its collection in 1953. However, the absence of additional collections over the past sixty years suggests that Threatened might more accurately reflect its true status.

Comments.

Rhodamnia daymanensis appears to be part of the “pearly” group ( Snow 2007) by virtue of its abaxial indumentum. Scott (1979) included this specimen in Rhodamnia blairiana var. propinqua (C.T. White) A.J. Scott.

Among the species of Rhodamnia in New Guinea occurring at elevations above 2000 meters with a similar abaxial indumentum, Rhodamnia daymanensis mostly closely resembles Rhodamnia lancifolia . The type collection of Rhodamnia lancifolia (2425 m) is approximately 25 km west of the type locality of Rhodamnia daymanensis (2250 m) in similar habitats. However, Rhodamnia lancifolia differs by its more narrowly elliptic leaves, a less pronounced petiolar sulcus, slightly impressed adaxial laminar midvein (vs. more deeply impressed in Rhodamnia daymanensis in the proximal half), and the more yellowish (and longer, on average) abaxial laminar indumentum. The adaxial leaf surface of Rhodamnia lancifolia , for which there are many collections,is nearly black when dried, which contrasts with the fucosus (dark greyish brown, Beentje 2010) dried color of Rhodamnia daymanensis . The flowers (presumably hypanthium and abaxial surfaces of calyx lobes and petals) of Rhodamnia lancifolia have a brownish-pinkish indumentum (Stevens & Veldkamp LAE 55582; isotype [L!]), whereas the floral indumentum of Rhodamnia daymanensis is mostly distinctly yellowish.

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 3. Rhodamnia daymanensis N. Snow. Photo of the holotype at A (L. J. Brass 22718).