Tryssophyton quadrifolius K.Wurdack & Michelang., 2019

Wurdack, Kenneth J. & Michelangeli, Fabian A., 2019, Systematics and relationships of Tryssophyton (Melastomataceae), with a second species from the Pakaraima Mountains of Guyana, PhytoKeys 136, pp. 1-21 : 1

Tryssophyton quadrifolius K.Wurdack & Michelang. sp. nov. Figure 2

Diagnosis.

Differs from Tryssophyton merumense in 4-verticillate, ovate, petiolate leaves, versus 10-16 verticillate, oblanceolate-lanceolate, subsessile leaves.

Type.

Guyana. Cuyuni-Mazaruni Region: Summit of Kamakusa Mtn. (i.e. on top of 4th escarpment of four); impenetrable elfin forest to 3 m, extremely dense and wet, rich in epiphytes, with Bonnetia (2 spp.), Brocchinia cf. tatei , Malpighiaceae , Melastomataceae , Cyperaceae spp., Weinmannia , Ilex cf. retusa , 5°52'50.9"N, 60°6'11.7"W, 1691 m elev., 8 June 2012 (fl.), K. Wurdack 5865 with E. Tripp, A. Radosavljevic, and J. Ralph (holotype: BRG!, isotype: US-3731242!).

Description.

Habit perennial, rhizomatous herbs; rhizomes persistent, fleshy, horizontal, to 10 cm long, 3-6 mm diam., rarely branched, bearing 1-2 leafy, erect, aerial stems per axis and older cup-shaped (collar to 0.3 mm high and centre sunken) aerial stem scars; adventitious roots fine, fibrous. Indument sparse on aerial stems, leaves, pedicels, hypanthium and sepal margins; trichomes simple, to 0.1 mm long, glandular, reddish. Aerial stems 8.5-11.5 cm tall, 0.9-2 mm diam., terete, purple, slightly flared at rhizome attachment, summit with cluster of leaves and often 1 secondary branch 1-2 cm long and crowned by another cluster of leaves. Leaves 4-verticillate, opposite pairs sub-equal in size, simple, petiolate, exstipulate; petioles 2-5 mm long (of slightly subequal length within whorl), ca. 1 mm diam.; lamina 2.1-5.2 × 1.0-1.9 cm, length:width ratio 2.2-3.7:1 (mean = 3.0, SD = 0.50, n = 11), symmetrical, ovate to lanceolate, membranous, apex acuminate, base cuneate, margin minutely serrate, with 6-12 teeth per side (2-5 teeth/cm); teeth 0.5-0.9 × 0.1 mm, first-order, spacing regular, projecting 0.2-0.3 mm from margin, sinus shape rounded, distal flank concave and proximal flank straight, apex long-attenuate; leaf tip with 1-3(13) adaxial scales, 0.6-1 × 0.1 mm, similar to attenuate teeth apices. Venation suprabasal acrodromous, with one pair of major (costal) secondaries 1/2 of the gauge of the midvein, joining the midvein 0.5-1 mm above the leaf base; and one pair of intramarginal secondaries <1/3 of the gauge of the midvein (poorly defined from tertiary thickness), joining <0.5 mm from base, traversing 0.2-0.8 mm from margin, distally fading into exterior tertiary loops; up to 12 interior tertiary veins per side, quaternaries random reticulate. Inflorescence terminal, pedunculate, bearing 1-4 flowers; peduncle 2.2-2.6 cm long, 0.5-0.7 mm diam. mid-length, terete, flaring at base, purple; bracts persistent, lanceolate, 1-1.3 × 0.3-0.4 mm, apex apiculate, margin entire. Flowers 4-merous, bisexual, pedicellate; pedicels 8.5-11.5 mm long, 0.4-0.6 mm diam. mid-length, terete, purple; hypanthium at anthesis ca. 2.5 mm × 2-2.5 mm (excluding calyx), campanulate, obscurely costate with thin ribs; calyx lobes 4, in bud narrowly triangular, ascending, protective of young corolla, at anthesis spreading, 0.8-1 mm tall, broadly triangular above short calyx tube ca. 0.4 mm high; petals ca. 9.5 × 5 mm, margins entire, in vivo red outside and pink inside. Stamens 8, incurved in bud with tips extending into hypanthium below point of filament attachment, slightly anisomorphic, with the antesepalous whorl larger than the antepetalous, glabrous; filaments 5-6 (antesepalous) or 4 (antepetalous) mm long, 0.2 mm diam., linear, pink in vivo; thecae 4.5 or 3.5 mm long, basifixed, connective basally prolonged, dilated below thecae, forming a thickened annulus that is more or less ventrally bilobate, thickening 0.8 or 0.5-0.6 mm diam., yellow in vivo; anther 0.1-0.2 mm wide at terminal pore. Ovary superior, ca. 1.8 × 1.3-1.5 mm, glabrous. Style ca. 10 mm long, 0.2 mm diam., curved, glabrous; stigma punctiform, minutely papillose. Capsule ovate, ca. 3 × 3.5 mm, crowned by persistent calyx. Seeds ovoid, ca. 0.7 × 0.4 mm (immature and partly collapsed), sparsely papillose, brown.

Etymology.

The specific epithet is derived from quadri - (Latin, four) and folium (Latin, leaf) and refers to the 4-verticillate leaves.

Distribution and ecology.

Tryssophyton quadrifolius is only known from the summit of Kamakusa Mountain where it was encountered as an infrequent epiphyte on moss and lichen covered branches and trunks of large shrubs. Scattered small plants with single stems were observed sporadically along the main trail transect cut along the north-south orientated narrow summit. The few reproductive plants were in a more sheltered spot on the western edge of the summit on a branch trail that was cut to a cliff edge for a view. Flowers and young fruit were collected in June. The summit of Kamakusa Mountain is covered by low montane evergreen cloud forest, 3-4 m tall, with dense thickets dominated by Bonnetia tepuiensis Kobuski & Steyerm. and B. roraimae Oliv. ( Bonnetiaceae ), Byrsonima pachypoda W.R. Anderson ( Malpighiaceae ), Miconia acutifolia Ule and M. silicicola Gleason ( Melastomataceae ), Raveniopsis microphyllus K. Wurdack ( Rutaceae ) and species of Weinmannia L. ( Cunoniaceae ) on a peat substrate overlying sandstone. Vascular epiphytes included species of Utricularia L. ( Lentibulariaceae ), Bromeliaceae and Orchidaceae .

Conservation status.

While the upper part of Kamakusa Mountain is presently pristine and undisturbed, the new species is a delicate epiphytic herb with few reproductive plants (2 of 15 aerial stems collected had buds, flowers and/or fruit) in an area of extremely limited montane habitat. The species is vulnerable to climate and land use changes, such as regional gold mining (see Wurdack 2017). Following the criteria and categories of IUCN (2012, 2019) and similar to the recently described Kamakusa endemic Raveniopsis microphyllus , Tryssophyton quadrifolius is given a preliminary status of Critically Endangered (CR) under geographic range criteria B1 (extent of occurrence <100 km2 (B1) and area of occupancy <10 km2 (B2a, number of locations =1; B2b, continuing decline projected).

Figures

Figure 2. Illustration of Tryssophyton quadrifolius (A-G) and T. merumense (H, I). A Habit (right view in flower) B young flower with anthers inflexed C flower with anthers erect and petals fallen D shorter antepetalous anther, dorsal E longer antesepalous anther, dorsal F longer anther, lateral G young fruit H habit I capsular, 3 - merous fruit. Sources: A-G Wurdack 5865 H Radosavljevic 165 I Wurdack 5870 (all US).