Eugenia roseopetiolata N. Snow & S. Cable, 2012

Snow, Neil, Rabenantoandro, Johny, Randriatafika, Faly, Rabehevitra, David, Razafimamonjy, N. Darie & Cable, Stuart, 2012, Studies of Malagasy Eugenia (Myrtaceae) - III: Seven new species of high conservation concern from the eastern littoral forests, Phytotaxa 48 (1), pp. 39-60 : 51-53

Eugenia roseopetiolata N. Snow & S. Cable , sp. nov. ( Figs. 2 , 7 ).

A congeneribis madagascariensibus combinatione characterum sequentium distinguitur: petioli rubri glandulis prominentibus flavidis; bracteolae breves et appressae; filamenta et petala albida.

Type: ― MADAGASCAR. Prov. Toliara: SW of Ft. Dauphin in Petriky Forest , W side of forest tract N of Lake Andrato lohorano, block P-1 of QIT-FER, 25°04’S, 46°49’E, 15 m, 19 November 1990, D. Faber-Langendoen 3557 (holotype MO! [sheet no. 4029290]) .

Tree to 4 meters. Indumentum on vegetative and reproductive parts shortly sericeous-villous (trichomes dibrachiate and mostly somewhat ferrugineous). Branchlets laterally compressed, smooth to slightly irregular, moderately sericeous, light brown; oil glands not visible; internodes ca. 1–2 cm long. Leaves thinly coriaceous, concentrated near branchlet tips, glossy emerald green above but dull (matte) citrine below (fresh; brownish when dry); venation brochidodromous. Stipules absent. Petioles 4.0– 6.5 mm long, deeply sulcate above, bright magenta to maroon (the pigment often extending into base of midrib and proximal region of laminar margin), oil glands prominent and distinctly yellowish in younger material, sericeous above (especially on emergence). Leaf blades (2.8–)4.0–4.7 x 1.8–2.3 cm, mostly elliptic (rarely obovate), base cuneate, apex and tip obtuse, margin slightly revolute, surface flat; adaxial surface sparsely sericeous (proximally) on emergence but becoming glabrate, oil glands indistinct but numerous (especially visible near base and along proximal margins), midvein slightly sulcate (proximally, becoming flush distally); abaxial surface sparsely sericeous-villous (becoming glabrate), oil glands moderate to common, faint (fresh of dried), secondary veins visible but not prominent; intramarginal vein 1.0– 1.5 mm from laminar margin at midpoint. Inflorescence a solitary axillary flower, or arising from a short brachyblast; pedicel 4–8. 5 mm long, terete, shortly sericeous-villous (trichomes dibrachiate), stiff but sometimes slightly curved, light green (fresh), often with minute triangular bract at base (bract with numerous oil glands of various sizes; apex of bract greenish or light brown). Bracteoles 0.5–0.8 mm long, ovate, scale-like, erect and stiffly appressed (in flower) against base of hypanthium (apex of pedicel slightly swollen underneath base of each bracteole), moderately sericeous. Hypanthium 2.0– 2.4 mm long, ca. 2.0 mm wide at base of calyx lobes, obconic, terete and light green (fresh), moderately sericeous-villous, ovary apex glabrous. Buds light green, densely but faintly yellowish-glandular, sparsely sericeous (trichomes dibrachiate, often brownish). Calyx lobes 4, 1.5–2.3 mm long, dimorphic (2 longer, 2 shorter), light yellow-green (when fresh), rounded, sparsely dibrachiate-sericeous above and below, oil glands below of distinctly different sizes, prominent and slightly protruding. Petals 4, 5.0– 5.7 mm long, widely ovate, glabrous above and below, white, sparsely and faintly glandular, relatively thick. Staminal ring densely short-villous, ca. 2.5 mm wide. Stamens ca. 90–110; filaments 2.5–5.5 mm, white; anther sacs ca. 0.7 mm long, subcylindrical, sub-basifixed, cream colored, apical gland on connective faint. Style ca. 6 mm long (material scant), glabrous, white; stigma terete but scarcely if at all capitate. Ovary bilocular; placentation axile; ovules arising from center of placenta. Fruit unknown.

Field characters:— Petioles bright magenta to maroon, sulcate and slightly sericeous above; leaf blades 4-4.7 cm long; petals, filaments and style white.

Distribution:— Petriky Forest ( Fig. 2 ).

Habitat and ecology:— White sand littoral forest.

Phenology:— Flowering in November. Fruits unknown.

Additional specimen examined (paratype): ― MADAGASCAR. Prov. Toliara: Petriky (Vohibary), 25°3’6.68”S, 46°53’45.24”E, 21 February 2007, E. Landry P165 (K! [seed source for Millenium Seed Bank], TAN) .

Etymology:— A Latinization that refers to the bright reddish petiole in living material.

Conservation status:— The species is known from Petriky forest. With just two collections ( Fig. 7 ) from a restricted forest, an AOO of 9 km 2, and a single subpopulation constituting a single location with an estimated number of less than 250 individuals, encompassed within or near a protected area (Mandena), E. rosapetiolata is assigned a preliminary status of “Endangered” (EN: D).

Although field studies have not attempted to count the number of individuals, substantial collecting in Petriky since the 1980s likely would found additional specimens if E. roseopetiolata were more common. Also, given that Eugenia arenicola , E. cassinoides , and E. cloiselii have been collected in the same general area in greater numbers, we tentatively estimate the total population of E. rosapetiolata to be less then 250 individuals.

Discussion:— Eugenia roseopetiolata most closely resembles E. cassinoides , but several aspects of the former appear to be distinct from the latter, including: the reddish color of the petioles that extends into the lower leaf margins and somewhat into the midvein of the laminar surface, and prominent yellowish oil glands on the petiole ( Fig. 7 ). Additional study of fresh material of E. roseopetiolata , E. cassinodies , and related material will be necessary to better understand variation between these taxa.

Figures

FIGURE 2. Distribution of species and selected specimens of Eugenia in southeastern Madagascar based on vouchered herbarium specimens and recently captured (but non-vouchered) digital images. Remaining forested areas (Petriky, Mandena, Sainte-Luce) along the coast are indicated in gray. In cases where the icons largely or completely overlapped based on geo-coordinates they have been separated slightly for easier viewing (e.g., E. ardyceae, E. stictophylla and E. cloiselii along the coast west of Tolagnaro). Many additional specimens of Eugenia from the region await identification or description and cannot be mapped confidently at the present time.

FIGURE 7. Eugenia roseopetiolata (from cultivated material at Kew). Top left: bark. Top right: petiole of freshly harvested material taken through dissecting scope. Middle left: flowering branchlet. Middle right: flowers. Bottom left: flower, post-anthesis, with petals and stamens removed. Bottom right: adaxial (top) and abaxial (bottom leaf surfaces).