Tridimeris chiapensis Escobar-Castellanos & Ortiz-Rodr., 2016

Ortiz-Rodriguez, Andres Ernesto, Escobar-Castellanos, Marcos Alberto & Perez-Farrera, Miguel Angel, 2016, Phylogenetic analyses and morphological characteristics support the description of a second species of Tridimeris (Annonaceae), PhytoKeys 74, pp. 79-95 : 84-87

Tridimeris chiapensis Escobar-Castellanos & Ortiz-Rodr. sp. nov. Figs 1 , 2 , 3

Type.

Mexico. Chiapas, Municipio de Berriozábal, Zona Sujeta a Proteccion Ecologica "La Pera", Campamento “Trepatroncos” carretera Berriozabal-Joaquin Miguel Gutierrez , km. 12 desvío a Montebello , 1081 m, 16°52'20.3"N, 93°19'32.5"W, 11 August 2016 (fl) Escobar-Castellanos M. A. 0689 (holotype HEM; isotypes: XAL, MO) .

Diagnosis.

Tridimeris chiapensis is phylogenetically related to Tridimeris hahniana with which it shares axillary and dimerous flowers and large and fleshy fruits. However, Tridimeris chiapensis differs in having flowers with glabrous sepals, a triangular white patch near the base of inner petals and 2-5 carpels per flower and glabrous fruits (Fig. 3 ), while Tridimeris hahniana has flowers with sepals densely tomentose outside, 1 or 2 carpels per flower and fruits densely covered with golden-brown hairs.

Tree 3-9 m tall and 3-14 cm DBH; young branches slightly pubescent, trichomes appressed and golden-brown in color, glabrescent with age. Leaves membranaceous to chartaceous, alternate, phyllotaxy distichous, 11-20 cm long to 3.5-8 wide, narrowly elliptic to obovate, the apex acute to acuminate, the base acute to obtuse, sometimes asymmetrical; upper surface glabrous, the lower side glabrescent; venation brochidodromus, 6-9 veins per side, pocket domatia in the axils of the main veins; the midrid impressed above and slightly canaliculate toward the base (sometimes with erect to appressed light-brown hairs), lateral veins barely elevated above; the midrib and lateral veins prominently elevated below and with sparsely light-brown hairs, lateral veins decurrent at midrid insertion; petiole swollen, 0.5-1 cm long, canaliculate, with sparsely light-brown hairs. Inflorescences always one-flowered, axillary, sometimes arising on leafless part of branches (ramiflory), the pedicel glabrous, 1-1.7 cm long, bearing 2-3 minute, densely golden tomentose and broadly ovate basal bracts. Sepals 2, connate, to 2 mm long × 4-5 mm wide, decurrent along the pedicel, broadly ovate, rounded at apex, glabrous inside and outside, the margins ciliate. Petals 4, in two subequal whorls, 8-14 mm long × 3-5 mm wide, lanceolate to triangular, green to yellowish green, glabrous inside and outside, the margins ciliate, acute at apex, the base truncate and cusped around the stamens; the outer petals, more or less thin, with faint venation, reflexed at anthesis; the inner petals thicker and fleshier and not reflexed with a shallow, more or less triangular white patch near the base. Stamens, c.a. 40, 1-1.5 mm long, extrorse, filament very short, apical part of connective expanded over the thecae, shield-shaped, ellipsoid to angulate, glabrous. Carpels, 2-5 per flower, to 2.5 mm long; the stigma more or less globose and essentially glabrous; style absent; the ovaries ellipsoid and more or less curved, like a small banana with sparsely light-brown hairs; the ovules, 12-18, lateral, in two rows. Monocarps, 1-4 per fruit, large and fleshy, 8-11 cm long × 3-5 cm wide, ellipsoid, the apex and base rounded, glabrous, shortly stipitate, stipes to 7 mm long; young monocarps green, yellow to light brown when ripe with a peach-like sweet odor; seeds lunate to wedge-shaped, 1.3-2.2 cm long with lamellate ruminations.

Habitat and ecology.

The type locality of Tridimeris chiapensis is locally named as "La Pera" and "Pozo Turipache" or "El Pozo" and it lies within the ecological state reserve La Pera, which is mostly covered by tropical rainforest. Thin soils, rough limestone outcrops, caves, crevices, sinkholes and almost no surface water that form a typical karst landscape can be observed around El Pozo ( Wake and Johnson 1989). Also, fogs forming cloudbanks are common throughout the year, though absent during the dry season ( Wake and Johnson 1989).

Tridimeris chiapensis forms part of the understory vegetation and it is associated with Mortoniodendron ocotense Ishiki & T. Wendt, Mortoniodendron vestitum Lundell, Trichilia moschata Sw., Neea tenuis Standl., Pseudolmedia glabrata (Liebm.) C.C. Berg, Quararibea funebris (La Llave) Vischer, Quercus lancifolia Schltdl. & Cham. and Heliocarpus appendiculatus Turcz. ( Escobar-Castellanos 2016).

Phenology.

The species was found in full bloom in August and bearing fruits in March and May.

Etymology.

The specific epithet is in honor of the Mexican state of Chiapas where the species was found.

Conservation status.

Tridimeris chiapensis is known only from the type locality at the ecological state reserve La Pera. According to the criteria established by the IUCN, it is possible to tentatively determine that the species is Critically Endangered [CR B1ab (iii)]. The Area of occupancy (AOO) of Tridimeris chiapensis is 0.314 km² and the Extent of occurrence (EOO) is 1.519 km², suggesting a very restricted overall distribution. Although the only known population of the species is located within a protected natural area, only 7 individuals of Tridimeris chiapensis in one hectare of sampling were recorded ( Escobar-Castellanos 2016). The 3000 ha of La Pera’s rainforest estimated by Espinosa (2014) and its species are threatened by non-sustainable activities (logging, fires, illegal settlements) and forests in this region are fragmented and only some remnants persist which are surrounded by roads, croplands and cattle pastures ( Medina et al. 2006, Luna-Reyes et al. 2015).

Additional specimens examined.

MEXICO. Chiapas, Municipio de Berriozábal: Zona Sujeta a Proteccion Ecologica "La Pera", Campamento “Trepatroncos” carretera Berriozabal-Joaquin Miguel Gutierrez , km. 12 desvío a Montebello , 1081 m, 16°52'20.3"N, 93°19'32.5"W, May 2014 (fr) Escobar-Castellanos M. A. 0599 (HEM), May 2015 (fr) Ortiz-Rodriguez A. E. 801 (XAL); Zona Sujeta a Protección Ecológica "La Pera", Predio "La Selva", desvío hacia San Joaquín, carretera Berriozábal-Joaquín Miguel Gutiérrez, Sistema kárstico, 14 km al NO de Berriozábal. Plot X, Tree No. 27, 1049 m, 19°52'50.45"N, 93°19'07.92"W, 11 August 2016 (fl) Escobar-Castellanos M. A. 0690 (HEM); Zona Sujeta a Protección Ecológica "La Pera", Predio "La Selva", desvío hacia San Joaquín, carretera Berriozábal-Joaquín Miguel Gutiérrez, Sistema kárstico, 14 km al NO de Berriozábal, 1050 m, 19°52'54.62"N, 93°19'09.77"W, 31 March 2014 (fr) Escobar-Castellanos M. A. 0556 (HEM) .

Figures

Figure 1. Distribution range of Tridimeris chiapensis Escobar-Castellanos & Ortiz-Rodr. (red dot) and Tridimeris hahniana Baill (black dots).

Figure 2. The 50 % majority-rule consensus tree from the Bayesian analysis of six cpDNA markers. Numbers on branches of the major clades indicate Bayesian posterior probabilities (PP), maximum likelihood (MLBS) and parsimony (MPBS) bootstrap values in that order. In red, the position of Tridimeris chiapensis Escobar-Castellanos & Ortiz-Rodr.

Figure 3. Tridimeris chiapensis Escobar-Castellanos & Ortiz-Rodr. A Dimerous flower B Large and fleshy fruits C Flower showing the pollen release and a triangular white patch at the base of the inner petals D Five carpels surrounded by numerous stamens E Leafy branches. Photographs by Marcos Escobar-Castellanos.