Rhodamnia makumak N. Snow, 2012

Snow, Neil, 2012, Five new species of Rhodamnia (Myrtaceae, Myrteae) from New Guinea, PhytoKeys 19, pp. 31-49 : 35-37

Rhodamnia makumak N. Snow sp. nov. Figures 1 4

Resembling other species of Rhodamnia having stellate trichomes but differing by its sessile to subsessile flowers and narrowly elliptic leaves with occasionally falcate apices.

Type.

Papua New Guinea. Milne Bay Province: E. of Mt. Suckling in valley of the upper Maiyu R[iver] c. 15 km WNW of Biniguni airstrip, ca. 9°40'S, 149°10'E, ca. 350 m, 7 Jul 1972, R. Pullen 8433(holotype: A! [no accession numer]; isotypes: BO n.v., BRI!, CANB!, L!, LAE n.v., K!, TNS n.v.).

Description.

Trees to 25 m. Buttresses present but low of stature; fluting or twisting absent. Bark of main trunk reticulate-flaky, brownish. Indumentum, where present (branchlets, petioles, abaxial leaf surface, distal portion of adaxial leaf mi dvein, peduncles, bracteoles, hypanthium, calyx lobes, adaxial petal surfaces), densely tomentose and velvety in texture, consisting of stellate, ferrugineous trichomes. Branchlets terete to compressed. Leaves opposite, more or less evenly distributed along branchlets, discolorous; venation perfect or imperfect suprabasal acrodromous, secondary and tertiary veins faint but visible adaxially, intramarginal vein faintly visible from adaxially, tracing irregularly between tips of secondary veins and ca 0.5 mm from blade margin. Colleters absent. Petioles 4.5-6.5 mm long, rounded in transverse section. Leaf blades 4.5-7.5 cm long, 1.4-2.2 cm wide, narrowly elliptic, base cuneate, margin flat, apex acuminate and sometimes falcate, tip (uppermost 10% of blade) acute; adaxial surface matte, midvein slightly sulcate more or less throughout to sometimes flush distally, tomentose proximally; abaxial surface orangish-velvety by virtue of indumentum, midvein projecting throughout. Inflorescence terminal and lateral, solitary or paired to mostly a fasciculate cluster of monads, the monads sessile or on pedicels up to 3 mm long. Bracteoles 1.8-2.3 mm long, 0.4-0.6 mm wide, linear, rigid, ascending to erect, the apex not reaching base of calyx lobes, persisting. Hypanthium campanulate; anthopodium (if present) up to 1 mm long; metaxyphylls absent. Calyx lobes 4, 2.2-2.7 mm long, 2 (of the 4 lobes) more or less rectangular (length-width ratio 3:2), slightly longer than the 2 shorter, broadly ovate (3:2) lobes; adaxial surface densely tomentose or somewhat less so basally and near margins, abaxial surface densely tomentose throughout. Petals (material sparse) 2-2.5 mm long, 2-2.3 mm wide, elliptic to ovate, tomentose above and below. Stamens ca. 30-40, filaments 2-3 mm long; anther sacs ca. 0.5 mm long, globose, sub-basifixed. Style 3.5-4 mm long, hairy below; stigma narrow to slightly capitate. Fruit not seen.

Phenology.

Flowering confirmed only for early July but likely also in late June; fruiting unknown but probably June to July and possibly longer.

Distribution.

Papua New Guinea, Milne Bay Province; known only from rainforest on a plateau of ca. 350 meters elevation.

Conservation status.

Data Deficient.

Etymology.

From the local vernacular name “makumak” as a noun in the nominative.

Vernacular name.

Makumak in the local Daga language.

Comments.

Rhodamnia makumak ispart of a group of species characterized by a hypothesized synapomorphy of stellate trichomes ( Snow 2007). Scott (1979) treated the type collection as Rhodamnia blairiana var. blairiana, which as presently understood occurs only in Australia ( Snow 2007). Dr. Gordon Guymer (BRI), who worked previously on Rhodamnia , likewise recognized the affinity of the type collection to Rhodamnia blairiana , judging from his specimen annotations.

Rhodamnia makumak is said to be a large tree with low buttresses (dimensions of buttresses lacking on label). The best diagnostic characters include the stellate, ferrugineous indumentum on leaves and hypanthium, which imparts a densely velvety appearance; the sessile to subsessile axillary clusters of flowers; and narrowly elliptic leaves bearing an acuminate and sometimes falcate apex. A provisional key to species with stellate trichomes follows.

Key to species of Rhodamnia with stellate trichomes

1	Leaves elliptic to broadly elliptic, 11-18 cm long, apex abruptly cuspidate-caudate	Rhodamnia kamialiensis N. Snow & W. N. Takeuchi
-	Leaves narrowly elliptic or narrowly ovate to ovate or elliptic, 4-12 cm long, apex acute to acuminate	2
2	Flowers pedicellate, pedicels mostly> 5 mm long; leaf apex acute	Rhodamnia propinqua C.T. White
-	Flowers sessile or nearly so; leaf apex acute to acuminate	3
3	Flowers sessile or pedicels to 3 mm; leaf apex acuminate and sometimes falcate	Rhodamnia makumak
-	Flowers pedicillate, pedicels 3.5-6 mm long; leaf apex acute to acuminate, rarely mucronate, never falcate	4
4	Seeds with a thin but pronounced equatorial ridge; plants of Australia, 650-1300 m	Rhodamnia blairiana F. Muell
-	Seeds lacking an equatorial ridge; plants of Australia and Papua New Guinea, sea level to ca. 500 m	Rhodamnia sharpeana N. Snow

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 4. Rhodamnia makumak N. Snow. Drawing of isotype at A (R. Pullen 8433). Clockwise from top: branchlet (bar = 1 cm); stellate trichome (bar = 0.1 mm); inflorescences (bar = 1 mm); style (bar = 1 mm); dehisced anther (bar = 0.3 mm).