Dinedema mariae A.Ramos, M.Lozano & Solano, 2025

Ramos-Roldán, Andrés E., Cuéllar-Martínez, Manuel, Lozano-Rodríguez, Miguel A. & Solano, Rodolfo, 2025, A new nothogenus and a new nothospecies in the subtribe Laeliinae (Orchidaceae) from Mexico, Phytotaxa 708 (1), pp. 1-15 : 3-6

× Dinedema mariae A.Ramos, M.Lozano & Solano , nothosp. nov.

( Figure 1 ).

Type: — MEXICO. Veracruz: Surroundings of Coatepec municipality, acquired in Miguel Hidalgo square, Coatepec, from an orchid seller between 2009–2010, cultivated by Mrs. Maria Juana Aguilar-Huezca, flowering in June 2023, A. Ramos 1 (holotype: CITRO-6297VER !, isotype: CITRO-6298VER !).

An intermediate nothospecies between its parent species, Dinema polybulbon and Nidema boothii , it is distinguished by its rhizomatous habit, fusiform, bifoliate pseudobulbs, two-flowered raceme as long as the leaves, sepals and petals yellowish-cream with reddish markings at the base, petals smaller than the sepals, lip white with a longitudinal yellow stripe at the basal half, its basal portion attached and parallel to the straight column, which bears two erect, triangular horns at its apex. It resembles Dinema polybulbon in its linear sepals and petals, obovate lip with a conspicuous claw, and straight column with two apical horns. It is similar to Nidema boothii in its fusiform, stipitate pseudobulbs and two linear, erect leaves.

Description: —Epiphytic sympodial, erect, scandent herb, up to 16.3 cm tall. Roots single, terete, flexuous, whitish. Rhizome 3.5–4.5 cm long between adjacent pseudobulbs, ca. 5.0 mm in diameter, creeping, consisting of 4 internodes, covered by tubular, brownish, imbricate, tight sheaths. Pseudobulbs 6.0– 7.5 cm long, 1.5–2.0 cm gross at the middle, 2- foliated, ellipsoid, stipitate, fusiform, laterally compressed, formed by 3 internodes; when young, covered by imbricate, brownish, scarious sheaths. Leaves 10.0–12.5 × 1.2–1.5 cm, erect, ensiform, lanceolate, subacute, coriaceous, sulcate on the adaxial surface, keeled on the abaxial surface, conduplicate at the base, without a defined petiole. Inflorescence apical, as long as the leaves, ca. 10.0 cm tall, arising from the developing pseudobulb, a 2-flowered raceme. Floral bracts 2.0– 2.5 cm long, lanceolate, conduplicate, acuminate. Flowers ascending, star-shaped; tepals yellow-cream with a purple flush towards the base; lip whitish on the blade, with a yellow stripe on the basal part that extends to the middle of the blade; column whitish, spotted with purple in the apex, around the stigmatic cavity, and toward the base, greenish at the entrance of the nectary, anther white pinkish. Sepals 17.5–18.5 × 3.0 mm, narrow-lanceolate, acuminate-apiculate, glabrous, recurved towards the apex, with lateral sepals slightly oblique. Petals smaller than the sepals, 14.0 × 2.0 mm, subparallel to the column at the base, recurved towards the apex, narrow-oblanceolate, acuteacuminate, slightly falcate. Lip 13.0 × 6.5 mm when extended, strongly arched-decurved, unguiculate; blade 9.0 × 6.5 mm, elliptical, rounded, longitudinally sulcate, with ascending margins; at the base with an oblong, canaliculate, papillose claw, 4.0 × 2.0 mm, parallel and touch the ventral surface of the column, with a triangular cavity at the base that fits into the nectary entrance. Column 7.5 mm long, 3.2 mm wide, lacking a foot, the body almost straight, widening from the base to the apex, ventrally channeled; clinandrium with lateral margins forming two erect, horn-like processes; the base of the column with a cavity that extends into the apical part of the ovary to form a nectary. Stigma cavity reniform, white, viscous; rostellum laminar, membranous. Ovary 1.9 cm long, 1.3 mm diameter near the apex, pedicellate, terete, straight, green, 6-ribbed. Anther apical, ovoid, with a longitudinal crest. Pollinarium consists of 4 unequal, yellow, compressed pollinia, with the two outer ones smaller, ovoid, connected by caudicula. Capsule not seen.

Distribution and ecology:— So far, × Dinedema mariae is only known from the foothills of the Cofre de Perote mountain system, between 1200 and 1500 m elev., surrounding the municipalities of Coatepec, Teocelo, and Xico, in the central region of Veracruz state, Mexico. In a remnant forest within this region, a specimen has been found whose vegetative morphology is similar to that of the nothospecies described here (rhizomatous growth habit, stipitate pseudobulbs bearing two apical leaves, and remnants of an apical inflorescence), but it has not been possible to observe it in bloom. Unfortunately, the specimen had disappeared during a recent visit to the locality.

The plant grows as an epiphyte on an unidentified species of Quercus Linneaus (1753: 994) , in a type of vegetation that originally consisted of pine-oak forest or cloud forest, which have been severely reduced, and now only isolated patches remain. It has been observed in bloom in June, producing two flowers from the developing pseudobulb. Dinema polybulbon flowers between September and March, while N. boothii blooms from August to May, according to García-Cruz et al. (2003) and the records consulted in GBIF and iNaturalist. The overlap in distribution and flowering suggests the possibility of intercrossing when populations of both species coexist, as observed in central Veracruz.

Etymology: —This new nothospecies is dedicated to Mrs. María Juana Aguilar-Huezca, from Coatepec, Veracruz, who has cultivated the specimen for almost 15 years and provided material for the description and lamina presented here.

Spatial distribution model: —For Dinema polybulbon , 25 models were generated. The most parsimonious model (AICc = 545.310234, ΔAICc = 0) had the following parameters: LQ with RM = 1 and an AUC of 0.9144. with an estimated potential distribution area of 34,696.04 km ². This area extends along the mid-elevation high hills and their foothill facing the Gulf of Mexico slope: Sierra Madre Oriental, northern mountains of Oaxaca, Sierra Los Tuxtlas, and the high lands of Chiapas ( Figure 2 . The variables contributing the most to the model were precipitation of the driest month (53.6%), and elevation (19.5%).

For Nidema boothii , 25 models were generated. The most parsimonious model (AICc = 1358.50114, ΔAICc = 0) had the following parameters: LQH with RM = 4, and an AUC of 0.9354, with an estimated potential distribution area of 163,226.8 km ². This area extends along the mid-elevation high hills and their foothills on both the Pacific and Gulf of Mexico slopes, including the Sierra Madre Oriental, Sierra Madre del Sur, Sierra Los Tuxtlas, the high lands of Chiapas, and the Sierra Madre de Chiapas ( Figure 3 ). Additionally, there are occurrence records in Guerrero and San Luis Potosi, although these regions show low probabilities. The variables contributing the most to the model were precipitation of the driest month (45.0%) and precipitation of the wettest quarter (20.2%).

The modeling estimated an overlap area of 17,646.32 km ² between the distribution ranges of D. polybulbon and N. boothii ( Figure 4 ), identifying three regions with a high probability of overlap: one in Sierra Norte of Puebla, a second in central Veracruz, where the known locality of × Dinedema mariae is located; and a third in Sierra Los Tuxtlas (Veracruz). These three areas could serve as potential hybridization zones for the two species.

Figures

FIGURE 1. × Dinedema mariae. A. Habit. B. Flower, lateral view. C. Flower, frontal view. D. Dissected floral pieces. E. Lip-columnovary, lateral view. F. detail of the lip and column touch each other, lateral view. G. Lip, ventral view. H. Column-ovary, ventral view. I. Column-ovary, dorsal view. J. Column, ventral view. K. Pollinarium. Plate by M.A. Lozano-Rodríguez, based on the type.

FIGURE 2. Map showing the spatial distribution model for Dinema polybulbon in Mexico. Map by M. Cuéllar-Martínez.

FIGURE 3. Map showing the spatial distribution model for Nidema boothii in Mexico. Map by M. Cuéllar-Martínez.

FIGURE 4. Map showing the overlap in the distribution areas of Dinema polybulbon (blue triangles) and Nidema boothii (black crosses) in the central region of Veracruz, Mexico, where the intergeneric hybrid between them, × Dinedema mariae, originated (yellow diamond). Map by M. Cuéllar-Martínez.