Miconia sparsiflora Almeda & R.B. Pacifico, 2025

Almeda, Frank & Pacifico, Ricardo, 2025, A new Panamanian species of Miconia (Melastomataceae: Miconieae), Phytotaxa 700 (1), pp. 107-114 : 108-113

Miconia sparsiflora Almeda & R.B. Pacifico , sp. nov. ( Figs 1–2 )

Type:— PANAMA. Bocas del Toro: Above Chiriquí Grande on a side road about 10 road miles below the Continental Divide , about 2 ½ miles east on that road, 8°55’N, 82°10’W, 300–400 m, 19 January 1989, fl. & fr., F. Almeda, G. de Nevers & G. McPherson 6340 (holotype: CAS-811783!; isotypes: BM!, CR!, G!, MEXU!, MO!, NY!, PMA!, SEL!, US!).

Diagnosis:— Miconia sparsiflora can be distinguished from M. gracilis , M. subspicata , and M. tenensis by its upper internodes and abaxial leaf surfaces that are covered with a mixture of black simple trichomes 1–1.5 mm long mixed with a brown amorphous branlike indumentum, somewhat shorter inflorescences 2.5–6.5 cm long with nodding flower buds, leaves that are obtuse to rounded at the base and covered with smooth ± appressed trichomes 1–2 mm long adaxially, and abaxially covered with a mixture of spreading smooth trichomes 0.5–2 mm long and minute amorphous branlike trichomes and glistening resinous-granulose trichomes throughout the blade surface, and petals that are distally irregularly lobed or somewhat emarginate.

Shrubs or small trees 1.5–3 m tall, cauline internodes of uppermost branchlets rounded, moderately to copiously covered with a mixture of smooth spreading blackish trichomes 1–1.5 mm long and a ground layer of brown amorphous branlike indumentum. Leaves of a pair equal to commonly unequal in size, concolored when dry, petioles 3–10 mm long, canaliculated adaxially and copiously covered with indumentum like that of upper internodes; blades 4.2–12.8 × 1.5– 4.5 cm, membranaceous when dry, lanceolate to elliptic-lanceolate, apex acuminate to caudate-acuminate, base obtuse to rounded, margin ciliate-denticulate, 3–5-nerved, the midvein and secondaries elevated for much of their length on the abaxial surface and spaced 5–13 mm apart at the wider portions of the blades, adaxially copiously beset with ± appressed smooth trichomes 1–2 mm long, abaxially prevailingly covered with spreading smooth trichomes 0.5–2 mm long on and between the elevated veins and also copiously and randomly covered with minute amorphous branlike trichomes and glistening resinous-granulose trichomes on and between the elevated primary, secondary and higher order veins. Inflorescence terminal often becoming axillary, racemiform, 2.5–6.5 cm long with flowers cernuous in bud and either solitary or ternate on the short (1–3 mm) lateral branches, moderately covered with an indumentum like the distal internodes, bracts of rachis nodes inconspicuous, 0.5 mm long, sessile and subulate, copiously beset with branlike indumentum; bracteoles evidently early deciduous and not seen. Flowers 5-merous, subsessile or on pedicels 0.5 mm long, hypanthia narrowly campanulate, 1–2 × 1 mm, densely covered with glistening resinous-granulose trichomes that partially conceal the surface at anthesis; calyx tube ca. 0.5 mm long, calyx lobes broadly deltoid undulations ca. 0.5 mm long and ca. 1 mm wide at the base, exterior calyx teeth five, 0.25 mm long and less than 0.25 mm wide at the base, barely exceeding the calyx lobes and largely concealing them. Petals 2.5 × 1.5 mm, white, obovate, the apex irregularly lobed or emarginate, resinous-granulose on the abaxial surface. Stamens 10, alternately somewhat unequal in length, filaments 1.5–2.5 mm long, glabrous, complanate; anther thecae 2.5–3 or 2 mm long, linear-oblong, the apical pore ventrally inclined (in larger antesepalous anthers) or dorsally inclined (in smaller antepetalous anthers); connective not prolonged below the thecae but ventro-basally bilobulate. Ovary (at anthesis) incompletely 2–3-locular and ca. 1/3 inferior, ± globose with a somewhat elevated rounded apex beset with resinous-granulose trichomes; styles glabrous or sparingly beset with minute deciduous trichomes, 3 mm long, ± straight; stigma expanded truncate-capitate. Berries ± subglobose at maturity, 3 × 3 mm, pale green with a flush of pink or pinkish-blue. Seeds irregularly ovoid, 0.36–0.57 mm long, 0.11–0.26 mm wide, brown, testa with rounded low-domed tuberculae, raphal zone oblong, ca. 80–100 % the length of the seed.

Paratypes: ― PANAMA. Bocas del Toro: Road from Fortuna Dam to Chiriquí Grande, 3.1 miles N of continental divide, 8°50’N, 82°15’W, 700 m, 10 March 1985, fl. & fr., G. McPherson 6776 (CAS!, MO-5859345!, MO-7060987!, PMA!). Veraguas: 11 km from Escuela Agricola Alto de Piedra in forest along Rio Dos Bocas, Atlantic slope, 08°33’N, 081°10’W, 400 m, 15 November 1974, fr., S. Mori & J. Kallunki 3145 (MO!).

Distribution, Habitat, and Phenology:— Miconia sparsiflora is known only from western Panama where it grows in the understory or along the margins of somewhat disturbed lower montane primary rainforest on the Caribbean slopes in Bocas del Toro and Veraguas provinces at elevations of 300–700 m ( Fig. 3 ). It never appears to be common at any one locality. A fruiting collection was made in November and both flowering and fruiting specimens have been collected in January and March.

Conservation Status:—All of the known localities for Miconia sparsiflora occur within the Mesoamerican biodiversity hotspot as delimited by Conservation International. This hotspot includes tropical and subtropical plant communities in political Central America (except easternmost Panama) as well as significant portions of southern and coastal Mexico ( Mittermeir et al. 2005). Of the three known populations of this species, only one is in a protected area in Veraguas province where the single locality falls just inside the southwestern border of Parque Nacional Santa Fe, a park that protects 72,636 hectares of mostly broad-leaved evergreen primary rainforest. According to the Autoridad Nacional del Ambiente of Panama (https://miambiente.gob.pa/), Santa Fe National Park, which was created in late 2001, is located in the highlands of Panama’s Central Mountain Range along the upper part of the Santa María River basin. It includes the entire montane area of northern Veraguas province, including both Pacific and Caribbean slopes in the district of Santa Fe.

The two collection localities in Bocas del Toro Province are just north of and outside of the southeastern sector of Bosque Protector Palo Seco. These westernmost localities have been subjected to disturbance and habitat fragmentation over many years. The EOO is 994.2 km ² and the AOO is 12.0 km². We recommend a conservation assessment of Endangered (EN): B2ab(iii) for this species.

Etymology: — The specific epithet emphasizes the few-flowered racemiform inflorescence and the even fewer developing berries on the infructescence.

Affinities:— Miconia sparsiflora appears to be related to a group of morphologically similar species that includes M. gracilis Triana (1872: 107) , M. subspicata Wurdack (1978: 1) , and M. tenensis Markgraf (1934: 178) . All of these species share a shrubby habit, subracemiform or subspicate inflorescences, 5-merous flowers with minute calyx teeth, mostly white petals and anther thecae, and anisomorphic stamens with the larger ones having ventrally inclined pores, and the smaller with dorsally inclined pores, and expanded truncate-capitate stigmas.

Miconia gracilis , which is widely distributed from southern Mexico (Guerrero, Oaxaca, and Veracruz) through Central America (except Guatemala and El Salvador) to Venezuela, Colombia, and Ecuador, is readily separated from M. sparsiflora by its modally larger entire leaf blades (9.5–24 × 4–9.5 cm) that are 3-nerved, acute to narrowly obtuse at the base, and completely glabrous on both surfaces ( Almeda 2009).

Miconia subspicata of Ecuador (Morona-Santiago, Napo, Orellana, Pastaza, and Sucumbíos), Peru (Amazonas, Loreto, and Pasco), and Brazil (Acre) has cauline internodes and hypanthia that differ from M. sparsiflora in being sparsely covered with subamorpho-stellulate trichomes on young growth but soon becoming glabrate. It also differs in having leaf blades that are entire and glabrous throughout, flowers that are erect or spreading in bud and at anthesis, petals externally minutely granulose and centrally sparsely glandular-setose, and by its pyramidate seeds with a smooth to vaguely granulate testa ( Wurdack 1980).

Miconia tenensis of Ecuador (Morona-Santiago, Napo, Pastaza, and Zamora-Chinchipe) and Peru (Amazonas and San Martín) differs from M. sparsiflora in having cauline internodes that are densely puberulous with sessile stellate trichomes, modally larger leaf blades (6–21 × 3–9 cm) that are glabrous adaxially with entire or obscurely undulateserrulate margins and an acute base, sparingly stellulate-puberulous hypanthia, and oblong petals that are externally granulose and sparsely stellulate-puberulous, and unlobed distally ( Wurdack 1980).

Miconia sparsiflora differs most notably from all of its close relatives in the indumentum characters of cauline internodes, leaf blades, and hypanthia that are highlighted in the abstract of this paper. A summary of salient morphological features comparing M. sparsiflora with its presumed relatives is included in Table 1.

Based on available specimen data there appears to be substantial elevational overlap between M. sparsiflora (300–700 m) and its presumed relatives. Miconia gracilis , the most widespread relative, also exhibits the broadest elevational range at 0–1580 m; M. subspicata occurs at 200–500 m; and M. tenensis grows at 230– 900 m.

Figures

FIGURE 1. Miconia sparsiflora. A. Habit. B. Indumentum detail of cauline internode. C. Representative leaf (abaxial surface). D. Representative leaf (adaxial surface). E. Indumentum detail of abaxial leaf surface along primary vein. F. Indumentum detail of adaxial leaf surface between primary and secondary veins. G. Cross section of flower (at anthesis) with petals and androecium removed. H. Petal (adaxial surface). I. Flower bud (profile view). J. Antepetalous stamen (lateral-dorsal view). K. Antesepalous stamen (lateral-ventral view). L. Fruiting hypanthiuum. M. Seed. (A–L drawn from CAS holotype; M drawn from McPherson 6776, CAS).

FIGURE 2. Miconia sparsiflora. Photograph of the holotype, F. Almeda et al. 6340 (CAS).

FIGURE 3. Distribution of Miconia sparsiflora. A. Central America and surroundings with Panama highlighted in red. B. Panama with distribution points in blue triangles.