Physeterostemon gomesii Amorim & R.Goldenb., 2014

Amorim, André Márcio, Jardim, Jomar Gomes & Goldenberg, Renato, 2014, Physeterostemon gomesii (Melastomataceae): the fourth species of this endemic genus in Bahia, Brazil, Phytotaxa 175 (1), pp. 45-50 : 45-49

Physeterostemon gomesii Amorim & R.Goldenb. , sp. nov. ( Figs. 1 , 2 , 3 )

Diagnosis: ––This species differs from all other species in the genus by its 5-merous flowers, 10 stamens, and 3-locular ovary, as all the other taxa have 6-merous flowers, 12 stamens, and 4-locular ovaries. It differs from Physeterostemon fiaschii in terms of the latter’s fascicled inflorescences covered with trichomes ca. 5 mm long and calyx with outer lobes 4–5.4 mm long. It differs from P. jardimii by its habit (rhizomatous subshrubs) and indumentum (strigose but also glandulose-setose in the former), as well as by the ovary apex (setose in P. jardimii ). It differs from P. thomasii in terms of its rhizomatous habit by having young stems and petioles covered with paleaceous trichomes and strongly bullate/foveolate leaves.

Type: –– BRAZIL. Bahia: Boa Nova, Parque Nacional de Boa Nova, Fazenda Liberdade , Região da Farofa , BR 030 entre o trecho Boa Nova ao Distrito de Valentim , ca. 5 km de Boa Nova, 14º21’25’’S 40º12’46’’W, 7 February 2013, fl., fr., A. M . Amorim, 8170, L. H . Daneu & L. C. J . Gomes (holotype CEPEC!, isotypes HURB!, K!, NY!, RB!, UPCB!) .

Shrub40–130(–140)cm tall. Young stems terete,densely strigose, trichomes 1.2–2 mm long, pale green and canescent to ochraceous when dried, appressed, mixed with short (0.1–0.2 mm) glandular projections that are denser in the nodal regions. Leaves opposite, each pair being slightly anisophyllous to isophyllous, petiole 2–4.8 cm long, trichomes the same as on the branches, leaf blade (3.7–)15.2–22.5 × 5.1–11.3 cm, elliptic to elliptic-lanceolate, base acute, apex acuminate to cuspidate, margins irregularly dentate to serrate, ciliate, 3-nerved to shortly 3-plinerved (the inner pair joining the midrib up to 5 mm above the base) with a faint additional submarginal pair, adaxially plane (not bullate), sparsely strigose, trichomes 0.3–0.6 mm long, appressed or with an erect base and strongly curved downward, abaxially plane (not foveolate), moderately strigose (denser on the main nerves), trichomes 0.3–0.6 mm long, erect and curved at the apex, otherwise similar to those on the abaxial surface, mixed with short glandular projections 0.1–0.2 mm long. Inflorescence terminal, corymbose, with 15–45 flowers, 2.6–3.5 × 2.4–4.5 cm, pale green, with trichomes similar to those on young stems; bracts 2.2–2.5 × 0.7–0.9 mm, narrowly triangular, apex acute, glabrous, margin strongly ciliate; bracteoles 1.3–2.2 × 0.3–0.6 mm, narrowly triangular, glabrous, margin strongly ciliate. Flowers 5- merous, pedicels 2–2.6 mm long (up to 4 mm long on the fruits). Hypanthium ca. 2.7 × 2.6–2.7 mm, campanulate, outer surface densely strigose, trichomes ca. 1 mm long, pale green and ochraceous when dried, inner surface and the torus glabrous. Calyx persistent, abaxially strigose, adaxial surface with sparse, short, glandular projections ca. 0.2 mm long; tube 0.3–0.7 mm long; inner lobes 1.2–1.8 mm long, triangular, apex rounded, margin irregular, shortciliate; outer lobes 1.4–1.7 mm long, subulate, setose-tipped. Petals 4.5–4.7 × 3.4–3.6 mm, white, glabrous on both surfaces, obovate, apex truncate to slightly emarginate, margin entire. Stamens 10, isomorphic, grouped together in a cluster on one side of the flower at anthesis; filaments 2.4–2.9 mm long; connective unappendaged, dorsally thickened; anthers 1.7–2 mm long, yellow, oblong, with a rounded apex in ventral view, straight (not slightly projecting backwards over the connective) in lateral view, with a single ventral pore, anthers ventro-basally with two short lobes below the filament insertion. Ovary half-inferior, the free portion 0.8–1 mm long, 3-locular, apex glabrous; ovules many on the large, globose, axial placentae; style curved, stigma punctiform. Capsules 2.9–3.6 × 3.2–3.5 mm, tearing longitudinally, with pericarp and adnate hypanthium persistent, placentae thick, perpendicular to the ovary axis, persistent. Seeds ca. 0.5 mm long, cuneate, testa smooth.

Distribution, habitat, and phenology: ––This species has been collected three times in the same locality in southern Bahia State ( Fig. 1 ). It grows in advanced secondary moist forests, in shaded areas. It has been collected with flowers in January and February and with fruits from the previous season also in February.

Conservation status: — Physeterostemon gomesii is currently known from only one population (although with many individuals) in the Boa Nova National Park. Habitat fragmentation and the small number of known populations represent high risks for the species. By IUCN (2014) criteria, this species is considered to be Critically Endangered (categories B1a and B1b) as its distribution range is less than 100 km 2, with continually declining habitat quality.

Etymology: ––The new species is named after Luís Carlos de Jesus Gomes, from the CEPEC Herbarium in light of his important technical support for the collections and fieldwork (especially with Melastomataceae ), and also one of the collectors of the type specimen.

Additional specimens examined (paratypes):— BRAZIL. Bahia: Boa Nova, Parque Nacional de Boa Nova, Setor Sul , Ramal para a Fazenda Liberdade , Setor da Farofa , 14°24’45’’ S, 40°07’46” W, 917m elev., 7 January 2013, fl., L. Y. S . Aona , 1988, G. M . Costa , W. O . Fonseca , J. G . Jardim & S . Simões ( CEPEC, HURB, K); ib., 850m elev., 22 February 2014, fl. fr., R . Goldenberg 1784, F . Michelangeli , L. H . Daneu & L. C. J . Gomes ( CEPEC, NY, UPCB, RB) .

Figures

FIGURE 1. Map showing the distributions of the species of Physeterostemon. Circle: P. gomesii; square: P. fiaschii; triangle: P. jardimii; star: P. thomasii.

FIGURE 2. Physeterostemon gomesii. A) Habit, with details of the adaxial surface of the leaf blade; B) Detail of the abaxial surface of the leaf blade; C) Bract; D) Bracteole; E) Calyx lobes, dorsal view; F) Flower bud, lateral view; G) Flower; H) Flower, longitudinal section; I) Antepetalous stamen, lateral-ventral view; J) Antesepalous stamen, lateral-ventral view; K) Detail of the anther, dorsal view; L) Antesepalous stamen, frontal view; M) Immature fruit, lateral view; N) Mature fruits; O) Detail of the fruit; P) Seed, lateral view (Amorim et al. 8170, Holotype).

FIGURE 3. Physeterostemon gomesii. A) Habit; B) Detail of the adaxial surface of the leaf blade; C) Detail of the abaxial surface of the leaf blade; D) Inflorescence, lateral view; E) Detail of flowers, one showing stamens; F) Immature fruits, from above (photos A–C, E–F by F. Michelangeli; photo D by L. Aona).