Eugenia petrikensis N. Snow & Randriat., 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 : 46-49

Eugenia petrikensis N. Snow & Randriat. , sp. nov. ( Figs. 2 , 5 ).

A congeneribis madagascariensibus combinatione characterum sequentium distinguitur: frutex 0.3–2 m altus; petioli

3.5–4.5 mm longi; folia 16.5–30 mm longa, 10–17.5 mm lata, elliptica, basi cuneata vel rotundata, apice obtuso; petala magentea ad marginem hyalina; stamina 20–30.

Type: ― MADAGASCAR. Prov. Toliara: District Tolagnaro ; forêt de Petriky, 25°05’S, 46°52’E, 26 October 1989, N. Dumetz 812, G. McPherson & R. Rabevohitra (holotype MO! [sheet no. 3778658]) .

Shrubs 0.3–2 meters at flowering. Branchlets moderately to densely sericeous on emergence but becoming sparsely so to nearly glabrous (trichomes dibrachiate, dense, clear to ferrugineous that become whitish brown); oil glands not visible or only faint (becoming more prominent in age), occasional; internodes ca. 1.0– 1.2 cm long. Leaves coriaceous, evenly distributed along branchlets, slightly discolorous, emerald green and slightly glossy above, citrine and matte below; venation brochidodromous. Stipules absent. Petioles 3.0– 4.5 mm, slightly sulcate above, eglandular but rugose-wrinkled throughout, glabrous, yellowish-green. Leaf blades 1.6–3.0 x 1.0– 1.7 cm, elliptic, base cuneate to rounded, margin somewhat revolute except near apex, laminar surface flat, apex and tip obtuse; adaxial surface sparsely sericeous towards base, oil glands absent, midvein slightly sulcate proximally but becoming flush distally; abaxial surface glabrous, oil glands absent, secondary veins invisible or faint with 4–5 veins arising on each side of midvein, sometimes slightly raised (dried material), intramarginal vein faint, 0.2–0.5 mm from margin at laminar midpoint. Inflorescence axillary or ramiflorous, consisting of monads or 3–flowered cymes, solitary, paired or generally in fascicles (sometimes densely so). Peduncles (or pedicels, if flowers solitary) 2–5 mm long, stiff, terete to compressed, medium green, glabrous or with a few scattered hairs. Anthopodia absent; metaxphylls mostly absent (present on one flower). Bracteoles 0.5–0.7 mm long, ca. 0.3 mm wide at base, narrowly triangular to triangular, scalelike, spreading, stiff, sparsely hairy, persistent in flower. Hypanthium 1.0– 1.5 mm long, 1.3–1.5 mm wide at apex at base of calyx lobes, obconic, glabrous, whitish to ivory or stramineous, oil glands common but small and inconspicuous, surface smooth, apex of ovary glabrous at base of style but villous towards staminal ring. Calyx lobes 4, 1.4–1.8 mm long, rounded to oblong, apex broadly rounded, glabrous, upper surface often magenta or cerise during anthesis and hyaline along margin, lower surface greenish. Petals 4, 3.0–4.1 x 2.1– 2.2 mm, ovate, oil glands sparse, magenta but hyaline on margins. Staminal ring villous, diameter 1.5–1.8 mm. Stamens 20–30, in 1 or 2 series; filaments ca. 2–3 mm long, whitish; anther sacs 0.7–0.9 mm long, globose to cylindrical, dorsifixed, bearing a single apical gland, cream colored. Style ca. 3 mm long, whitish, glabrous; stigma punctiform (scarcely if at all capitate). Locules 2; placentation axile, capitate, ovules 5–7 per placenta and radiating irregularly from placenta. Fruit (dimensions not measured) globose, glabrous, yellow at maturity, apex crowned by persistent calyx lobes.

Field characters: ―Shrubs up to 2 meters tall; flowers often ramiflorous in clusters and relatively small; hypanthium glabrous; calyx lobes sometimes with three relatively prominent veins; petals magenta; stamens relatively 30 or less. ( Fig. 5 ).

Distribution: ―Known only from the eastern part of Petriky Forest ( Fig. 2 ) and Ambinanibe Forest in Toliara Province in southeastern Madagascar. Ambinanibe Forest (not labeled in Fig. 2 ), only infrequently indicated on maps and from digital sources, is the highly fragmented area west of Tolagnaro, north of Lac Andriambe, an area of active mining operations.

Habitat and ecology: ―Growing in full sun (or more rarely in shade) in low forest on littoral sands from 0–10 meters elevation.

Phenology: ―Flowering late October to February; fruiting from December to March.

Etymology: ―The specific epithet is based on Petriky Forest ( Fig. 5 ).

Vernacular name:— Ropasy lahiny. Ropasy is a contraction of rotry and fasiky, the former of which is a generic vernacular name used for species of Eugenia and Syzygium around Tolagnaro. Fasiky refers to sand; thus ropasy means “ Eugenia that grows on sand”. When more than one species of a genus occurs locally a second name often is added for distinction, such as lahiny (male) or vaviny (female). The name ropasy is also used in Mandena (north of Tolagnaro) for Eugenia arenicola H. Perrier , another species from littoral forests in the general region.

Conservation status: ―The type gathering is in or near the eastern part of conservation zone P 1 in Petriky Forest ( Fig. 2 ; see also Lowry et al. 2008). The paratype ( Fig. 5 ) was from a non-protected and highly disturbed area. Although herbarium material of Eugenia petrikensis currently is known only from the type gathering, the species has been observed and photographed recently at Ambinanibe Forest (25°02’35’S, 46°56’04”E) growing in full sun or rarely in shade. With an AOO of 18 km 2, and 2 subpopulations, one in a protected area (Petriky), E. petrikensis is assigned a preliminary status of “Endangered” (EN: B2ab[iii]).

Discussion: ― Eugenia petrikensis may be more common than suggested by the known number of herbarium specimens. Its vegetative and floral morphologies most closely resemble those of E. ardyceae N. Snow ( Snow 2011) , which also occurs in the Tolagnaro region ( Fig. 2 ). However, the pedicillate flowers with glabrous hypanthia of R. petrikensis contrast with the sessile to subsessile flowers with sericeous-villous hypanthia of E. ardyceae . The dibrachiate trichomes of E. ardyceae on younger leaves are highly asymmetrical (i.e., arms of differing lengths [ Snow 2011]), which contrast with the more symmetrical trichomes in the emerging foliage of E. petrikensis . The calyx lobes on the type specimen of E. petrikensis have 3 straight and equally-spaced vascular bundles that converge apically slightly inside of the margin (magnification required), but it is uncertain if this trait occurs in all specimens.The leaves, inflorescences, and flowers of E. urschaiana H. Perr. var. urschiana also somewhat resemble those of E. petrikensis (e.g., M. Ursch 17, holo: P! [image seen]). However, E. urschaiana var. urschiana occurs ca. 1300 km north of Tolagnaro at ca. 250 m. elevation in forests at or near Analamazaotra ( Perrier 1953a, b) ("Analamazoatra" on herbarium label).

More detailed field surveys are urgently needed for this species.

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 5. Eugenia petrikensis. Upper left: bark of main bole. Upper right: sessile to subsessile inflorescences. Lower left: emerging leaves with whitish indumentum. Lower right: mature leaves; abaxial (upper) and adaxial (lower) surfaces. (No voucher; photos by D. Rabehevitra).