Dictyanthus nichongus L. O. Alvarado, R. Sanchez et A. Lopez 2022, sp. nov.
Creators: name: Alvarado-Cárdenas, Leonardo O.
name: Hernández, Alexis López
name: Crisóstomo, Raúl Sánchez
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Gentianales
Apocynaceae
Dictyanthus
Dictyanthus nichongus

description: Dictyanthus nichongus L.O. Alvarado, R. Sánchez et A. López sp. nov. (Figs. 1 –4)
Type:— México. Jalisco: Municipio Tomatlán. Camino hacia “ La Compuerta ” ca. 1 km del poblado de José María Morelos, cercano a la Laguna de Chalacatepec. 4 June 2021, R. Sánchez 1 (fl.) (holotype FCME!; isotype MEXU!).
Dictyanthus nichongus is morphologically similar to D. macvaughianus but differs by its smaller flowers, corollas yellow to almost purple corolla with parallel to reticulated purple lines, gynostegial corona lobes rhomboid, and style head conic, reddish to purple, and exserted from the corolla tube.
Twining vines, base suberized or slightly lignified, root not observed. Stems with indumentum hirtulose, more or less homogeneously distributed, made with uncinated or straight trichomes (long and short), dense to sparse, buds with a tuft of straight long trichomes. Leaves: stipular colleters 0.5‒0.7 mm, 0‒2, axilar; petioles (1.5‒)4.6‒5.5(‒7.5) cm long, puberulent with short straight trichomes, distally with scarce uncinated trichomes; blade membranous, ovate to broadly-ovate, 4.3‒6.6 (10.6) × (1.8)2.3‒5 (6.8) cm, with (5‒)7‒8 secondary veins, surfaces scarcely pubescent with both long and short uncinated trichomes distributed on the blade and veins, margins wavy to straight, base cordate, lobes 1.3‒1.9 cm long, divergent, apex acute; laminar colleters orange, 2‒4 at the base of the blade. Inflorescences racemose, with 1‒4 flowers open, indumentum similar to the stem in the following structures; peduncle 5.0‒ 9.3 mm long; bracts 2.5‒3.1 × 0.5‒0.7 mm, linear to lanceolate; pedicels 1.2‒1.7 cm long. Flowers with valvate aestivation: Calyx lobes lanceolate, 7.0‒9.9 × 2.2‒2.5 mm, adaxially glabrate or glabrous, abaxially pubescent with both long and short uncinated trichomes, mostly at the margin, with 1 colleter between the lobes. Corolla yellowish to almost purple, campanulate-rotate, deeply sacciform, 1.8‒2.0 cm in diameter, abaxially diminutively pubescent, adaxially glabrous, tube 5‒6.4 × 9.8‒10 mm, with vertical and parallel purple lines, limb 1.0‒ 1.35 mm long, reflexed, lobes ovate, 6.5‒8.3 × 6.5‒7.6 mm, patent, apex rounded to truncate, margin revolute, limb and lobes with reticulated pattern to completely purple-colored, adaxially glabrous or short and scarce straight trichomes, abaxially hirtulose; gynostegial corona 5‒ lobed, reaching the mouth of the tube to slightly exserted, staminal elements 1.7‒2.1 × 1.4‒1.7 mm, rhombus-shaped, apex rounded, white to yellowish, lobes connate at the corolla tube, adnate basally to the stipe of the gynostegium through a thick septum; gynostegium ca. 3.6 × 3.3 mm, pentagonal, stipe 1.8‒2 mm long; corpusculum ca. 0.25 × 0.12 mm, sagittate, dark brown; pollinia 0.7‒0.9 × 0.3‒0.33 mm, apically sterile and excavated; style head yellow, distally reddish to purple, convex, conical, 2.7‒3.2 mm tall, exserted, base pentagonal, apex rounded, slightly bilobed. Follicle brown with white-yellowish irregular stripes, fusiform, 6.5‒7 cm, with 35‒40 arcuate or straight projections. Seeds nearly circular to obovate, 5‒5.8 × 3.8‒5 mm, coma 2‒2.5 cm long.
Etymology: —The specific epithet is an anagram of the word “ chingón ”, which is a Mexican slang term with several meanings (Montes de Oca 2010, RAE 2021), one of them being “remarkable or of high quality”, herein used as an adjective.
Distribution & habitat: — Dictyanthus nichongus is only known from two localities in Jalisco. One of them is the population of the type specimen collected in Chalacatepec deciduous forest; the second locality corresponds to photographs posted on social media (Fig. 1A, 3A) from the locality of Tenamaxtlan, Municipality of Tenamaxtlan, for which we have no further information. The area of Chalacatepec belongs to the Pacific Coastal Plain, a physiographic region of Jalisco, Mexico. The new species is scarce and no more than 50 individuals were observed in the area. The population can be found between 20 and 45 m elevations. We observed a fly, probably Sarcophagydae, visiting the flowers, but we did not observe if the pollinaria were carried out, nor did we perceive an odor from the flower at the time (Fig. 1. D).
Phenology: —The specimen were collected with flowers and fruits in June.
Provisional conservation assessment: — The individuals of this species are restricted to Jalisco, Mexico, and two populations are known; one from the type locality close to the Chalacatepec beach, Jose Maria Morelos, Municipality of Tomatlan (Fig. 1 B-D, 2, 3B), and the second from an observation, recorded only by photographs, in the locality of Tenamaxtlan, Municipality of Tenamaxtlan, Jalisco (Fig. 1A, 3A). According to the people of José María Morelos, a hotel project is about to be carried out in the region, which could impact negatively on the vegetation where the population of Dictyanthus nichongus grows.The information about its population, phenology, and distribution is scarce, and the imminent habitat fragmentation and land-use change could place the plant populations at risk. Considering that we only know data from the type locality, together with the anthropogenic impact, we suggest the category of Critically Endangered B 2ab(ii) according to the red list criteria of the IUCN (2019).
Notes: — Dictyanthus is a morphologically interesting genus due to their flowers with a reticulated pattern of colors, sacciformed corollas, palmatilobed gynostegial corona with diverse morphology and fused to the corolla. This new species highlights Mexico as a center of diversity (17 spp.) and endemism for the genus (88%). Additionally, Dictyanthus nichongus increases the number of species of the genus in Jalisco to eight (Fig. 3), which places it, along with Oaxaca, the state with the highest diversity of Dictyanthus (Alvarado-Cárdenas et al. 2020).
The individuals of D. nichongus are distinct from all known species of the genus, but show some similarity with those in D. macvaughianus (Stevens 1988). Both species have corollas with pronounced sacs between the corona, with mainly parallel lines, and the stylar head apex is convex (Fig 3A–B, D). Dictyanthus nichongus has a flower diameter of 1.8‒2.0 cm, yellowish to almost purple with purple lines, rhombus-shaped corona lobes, and reddish to purple stylar head apex exserted from the corolla tube (Fig 1, 2). While D. macvaughianus has a flower diameter of 3 cm, brownish with purple to gray lines, linear-spatulate corona lobes, and the stylar head apex is pink and included in the corolla tube (Stevens 1988; Fig 3D). Dictyanthus parviflorus shares some similarities with D. nichongus in their campanulaterotate flowers with pronounced sacs between the corona lobes (Fig 3E). The former differs by its reticulate pattern in the corolla tube, linear-lanceolate gynostegial corona, and its gynostegium and stylar apex included in the corolla. Dictyanthus tuberosus showed some resemblance with the new species in its small and purple flowers with parallel lines in the corolla tube. It differs by its campanulate corolla, and gynostegium and stylar head apex deeply included in the corolla (Fig 3I).
description: Published as part of Alvarado-Cárdenas, Leonardo O., Hernández, Alexis López & Crisóstomo, Raúl Sánchez, 2022, A remarkable new species of Dictyanthus (Apocynaceae, Asclepiadoideae, Asclepiadeae, Gonolobinae) restricted to Jalisco, México, pp. 178-184 in Phytotaxa 558 (2) on pages 179-182, DOI: 10.11646/phytotaxa.558.2.2, http://zenodo.org/record/7002925