Pilea matama A.K. Monro, 2009

Monro, A. K., 2009, A new species of Pilea (Urticaceae) from the Talamanca Mountains, Costa Rica, Phytotaxa 2, pp. 24-28 : 25-28

Pilea matama A.K. Monro , sp. nov ( Fig. 1 . & Fig. 2 )

Species P. imparifoliae similis sed costa et nervis lateralibus foliorum supra prominentibus, foliis ad marginem laciniatis vel sinuatis, inflorescentiis staminalibus majoribus atque capitatis, floribus staminalibus majoribus, seminibus majoribus, differt

Type:— Costa Rica, Limón, P. N. La Amistad, Cuenca del Río Banano, Fila Matama, buffer zone for Parque Nacional La Amistad , ‘ La Ventana’, 09°48’56.4120”N, 83° 09’49.3560”W, 1200 m , A. K. Monro & D. Solano 5808 ( INB!- holotype; BM!, CR!, PMA!, MO!).

Herb to 25 cm; epiphytic, epipetric or terrestrial. Stems prostrate, occasionally erect, drying dull-yellow green, pale grey-green or dark green-brown, glabrous or occasionally brown peltate-glandular at flowering nodes, the cystoliths elliptic to punctiform or absent, the internodes 2.5–10.0 × 0.675–2.0 mm, angulate to square in cross-section. Stipules 0.5–0.675 mm, deltate, drying red-brown to dark brown. Leaves petiolate, distichous, petioles at the same node subequal or unequal by ratio 1:1.5–2.5, major petioles 0.75–2.5 mm, minor petioles 0.5–1.5 mm or subsessile, glabrous; laminas of leaves at the same node unequal by ratio 1:1.5– 3.8, the major laminae in a pair 6–28 × 4–11 mm, elliptic or obovate, sub-chartaceous to chartaceous; pinnately nerved, the secondary nerves 4-6 pairs, 45–60° to the midrib, crookedly curved; upper surface drying dark green or dark brown, glabrous, cystoliths fusiform, " V " shaped and " Y " shaped, or absent, midrib and secondary nerves prominently raised; lower surface drying pale grey-green, glabrous, eglandular, midrib and secondary nerves not raised; base symmetrical, decurrent; margins sinuate to laciniate, the basal 1/3 to 1/ 2 entire; apex asymmetrically tridentate; minor laminae in a pair 4.0–10.5 × 2.5–6.5 mm, ovate to elliptic, the base asymmetrical, cordate/cuneate, margin sinuate, otherwise as major laminae. Inflorescences 6–15 per stem, unisexual, rarely bisexual, staminate and pistillate inflorescences asynchronous, staminate inflorescences and infructescences synchronous, infructescences frequently including receptive pistillate flowers; bracts 0.375–1.0 mm; bracteoles 0.5–0.75 mm. Staminate inflorescences 1 or 2 per axil, 7–20 mm, bearing 5–39 flowers in a compact head; peduncle ¾ or more inflorescence length, glabrous, occasionally with cystoliths present; pedicels 0.5–0.75 mm, glabrous. Staminate flowers 2.5 × 1.5 mm immediately prior to anthesis, green-brown; tepals 4, 2.5 mm, glabrous, the subapical appendage 0.75 mm, corniculate, glabrous; stamens 4. Pistillate inflorescences solitary, 1.5–6.0 mm, bearing 3–16 flowers in a compact head; peduncle 1/ 3 to 1/2 inflorescence length, glabrous; pedicels 0.5–0.75 mm, glabrous. Pistillate flowers 0.75–1.0 mm, adaxial tepal 0.675–1.25 mm, oblong, elliptic or ovate, the dorsal tepal appendage ca 0.5 mm, oblong or ovate; the lateral tepals 0.5–0.675 mm, asymmetrically ovate. Infructescences 5–12 mm; peduncle 2/3 to 3/4 infructescence length; achenes 1.75–2.0 × 1.0 mm, compressed, asymmetrically ellipsoid, the margin narrowly thickened.

Distribution:—Provinces of Limón and Cartago, the Caribbean flank of the Talamanca Mountains, Matama ridge, at 1300-1500 m in wet tropical montane forest.

Etymology:—Refers to locality of all known collections of this species, Fila Matama.

Additional specimens examined (paratypes):— COSTA RICA: Cartago: Turrialba, Parque Nacional Barbilla, cuenca de Martina, Sendero Barthon, Quebrada Avispa, 09°55’15”N, 83°23’55”W, 1600 m, 8 Mar 2001, E . Mora 1862 (INBio, MO)

Limón: El Progreso, on the avioneta trail to Fila Matama, Valle de La Estrella , 09°47’18”N, 83° 08’45W, 1350 m, 19 Apr 1989, G . Herrera & A . Chacón 2658 ( BM, MO); Zona Protectora Río Banano, drainage of Río Banano , Fila Matama, buffer zone for P. N . La Amistad, ‘ Barranco’ plot by camp, 09°48’49.3560”N, 83° 10’02.1000”W, 1300 m, 23 Oct 2007, A. K . Monro & D. Santamaría 5761 ( BM, CR, INB, MO, PMA); drainage of Río Estrella, Fila Matama, buffer zone of Parque Nacional La Amistad , 09°48’16.6680”N, 83°10’10.6320”W, 1400–1500 m, 24 Oct 2007, A. K . Monro & D. Solano 5770 ( BM, CR, INB, MO, PMA); drainage of Río Estrella, Fila Matama, Parque Nacional La Amistad , ‘point 55’, 09°48’06.7320”N, 83°10’33.7080”W, 1400–1500 m, 27 Oct 2007, A. K . Monro & D. Solano 5771 ( BM, CR, INB) .

Discussion:—This species falls into Weddell’s (1869) Heterophyllae species group and Killip’s (1960) Centradenoideae species group. Pilea matama A.K. Monro is characterised by anisophyllous distichous leaves with the nerves of the adaxial leaf laminae prominently raised and frequently lower surface lacking cystoliths. Pilea matama closely resembles P. imparifolia Weddell (1852: 212) which also occurs in Costa Rica. The two species may be readily distinguished on leaf morphology, staminate inflorescence arrangement and morphology, staminate flower size and achene size as summarized below:

Pilea matama also resembles P. trichomanophylla A.K. Monro which occurs in Panama. The two species may be readily distinguished on leaf anisophylly and morphology, stipule morphology, and achene size as summarized below:

Figures

FIGURE 1. A. Disposition of leaves and inflorescences, Monro & Solano 5770 (Photo A.K. Monro). B. Habit in the field habit, Monro & Solano 5848 (Photo A.K. Monro). C. Staminate inflorescence with flower at anthesis, Monro & Santamaría 5761 (Photo A.K. Monro). D. Pistillate inflorescence with receptive flowers, Monro & Solano 5808 (Photo A.K. Monro).

FIGURE 2. A. Habit and stem. B. Variation in leaf shapes. C. Adaxial leaf surface. D. Stipules. E. Staminate inflorescence. F. Achene and persistent perianth. (A, C-E based on Monro & Solano 5808; B based on Monro & Solano 5808 and Monro & Solano 5771).