Gonolobus leotzinii S. Islas & D. Quintos-Baez, 2024

Gonolobus leotzinii S. Islas & D. Quintos-Baez , sp. nov. ( Fig. 1 View FIGURE 1 ).

Type:— MEXICO. Jalisco: Municipio Zapotitlán de Vadillo, 3.7 km al NE del predio El Borbollón, 1680 m, 19.5078°N, 103.6879°W, 15 April 2014, V. Quintero 497 (holotype MEXU 1546341!).

Diagnosis:— Gonolobus leotzinii is similar to G. uniflorus by having rotate, green corollas, with a very faint reticule, lobes with a whitish-green margin and tips of the lobes twisted, as well as staminal appendages of brownish-purple tones. However, G. leotzinii has sepals 3.48–5.08 mm long (vs. 7.5–10.5 mm) and a corolla with a diameter of 1.5– 1.75 cm with ovate lobes (vs. greater than 2.5 cm with lanceolate lobes), limb densely pilose (vs. glabrous) and the gynostegial corona with cucculate lobes (vs. patent).

Description:— Herbaceous perennial vines; latex white. Stems cylindrical, pubescence along two main lines, more dense on the nodes, glabrescent with age, trichomes simple 0.36–0.50 mm long. Leaves petiolate, petioles 1.54–2.86 cm long, trichomes simple, denser than on the stem and at the union with the lamina; lamina 4.64–8.47 × 1.39–2.69 cm, elliptical to lanceolate, base cuneate to subcordate, sometimes acute, lobes 6.36–8.12 × 6.38–9.95 mm, apex acuminate, abaxially and adaxially with multicellular simple trichomes, sparse all over the surface, on the adaxial side denser on the veins, margins entire, ciliate; colleters 0.15–0.6 mm long, 2–4 on the base of the blade, yellowish, conical to napiform. Inflorescences extra-axillary, one per node, cymose, peduncles 3.37–5.6 mm long, pubescent; pedicels 1.82–2.54 cm long, with multicellular simple trichomes, similar to the peduncles, denser than on the rest of the vegetative parts; bracts 1.71–3.59 mm long, lanceolate, deciduous, with dense indument all over the surface. Calyx green on the apex, turning white-yellowish toward base; sepals 3.48–5.08 × 1.28–1.56 mm, lanceolate, apex acute, indument with multicellular trichomes abaxially, 0.18 mm long; colleters absent at the base of the sepals. Corolla 1.5–1.75 cm diameter, green with faint reticulation of a darker green, 5-lobulate, rotate, lobes 6.54–8.27 × 3.43–4.36 mm, ovate, apex rounded with a revolute mucro, contorted, longitudinal fold marked on the abaxial face, multicellular trichomes on both surfaces, those on the adaxial face more abundant at the base and in a line along the margin of the lobe, those on the abaxial face arranged on the fold, limb ca. 1.31 mm wide, densely pilose, multicellular trichomes ca. 0.32 mm long, white; faucal annulus ca. 0.31 mm tall, pentalobed, green, margin crenate; gynostegial corona 3.76–4.35 mm diameter, ca. 0.61 mm de tall, with cucculate lobes, each lobe having a three-lobed appearance, yellowish-green; anthers with dorsal appendages 1.93–2.50 × 1.41–1.75 mm, laminar, reflexed, rectangular in general view, bilobed, lobes rounded, apex of anther rounded to slightly acute, with a membrane folded towards the stylar head; pollinaria corpuscles 0.16–0.26 × 0.36–0.41 mm; pollinia 0.73–0.85 × 0.33–0.39 mm, arranged horizontally; style head 3.68–3.79 mm diameter, pentagonal, apex greenish-yellow, flat to convex, without stipe, styles 2.25–2.43 mm long, ovaries 1.01–1.07 × 0.44–0.49 mm, apocarpic. Follicles and seeds not observed ( Fig 2 View FIGURE 2 .).

Distribution and habitat:— This species is distributed in the states of Jalisco and Michoacán in the Trans-Mexican Volcanic Belt ( Fig. 3 View FIGURE 3 ), in mountain cloud forest and pine-oak forest, between 1680–2000 m.

Phenology:— Flowering between February and May. Fruiting unknown.

Conservation status:— Gonolobus leotzinii is only known from one population in Jalisco and two in Michoacán. Based on this information an area of occupation(AOO) of 16 km 2 and the extension of occurrence(EOO) of 447.864 km 2, was estimated. The population in Jalisco is located in an area adjacent to the Nevado de Colima Volcano National Park, whereas the populations of Michoacán are close to cultivated and urban areas like Uruapan, Tingambato, Ziracuaretiro and Nuevo Parangaricutiro. These localities are in the center of the state, where a high rate of deforestation has been reported especially for avocado cultivation ( Barsimantov & Navia-Antezana 2012; Loya-Carrillo & Mass-Caussel 2020). According to IUCN (2024) criteria (B2ab(ii)), G. leotzinii is here proposed to be Endangered (EN).

Knowledge about the distribution of this new species is still limited. Considering the location of the records, the few known populations are located adjacent to areas where land use change increases the risk of its conservation. For these reasons, we emphasize the importance of integrating this new species into conservation plans and strategies in the states of Jalisco and Michoacán.

Etymology:— The name “leotzinii ”, is composed of the name Leonardo and the suffix “tzin”, which in the Nahuatl language denotes veneration, respect, and admiration for the person. This species is dedicated to our teacher and colleague Dr. Leonardo O. Alvarado-Cárdenas, who is a taxonomist specializing in Apocynaceae , a family to which he has dedicated most of his work.

Additional specimens examined:— MEXICO: Michoacán: Municipio Tingambato, cerro Comburinda, a 2 km al SE de Tingambato, 1953 m, 19,4733°N, 101.8049°W, 31 May 2015, M. Sales Figueroa 241 (MEXU). Municipio Uruapan, fondo de una cañada en la ladera sur del Cerro de la Cruz, 1780 m, 19.43822°N, 102.04417°W, 25 February 2024, V. W. Steinmann & Y. Ramírez-Amezcua 9144 (IEB).

Observations from iNaturalistaMX:— MEXICO: Jalisco: Municipio Zapotitlán de Vadillo, s. l., 1680 m, 19.5079°N, 103.675533°W, 16 April 2014. V. Quintero-F. 5125792 (iNaturalist: https://mexico.inaturalist.org/ observations/5125792).

Taxonomic remarks:— In the latest review of Gonolobus for Mexico, Cervantes (2023) estimated 42 species, 26 endemic to the country. Shortly after, three more species were published ( Pío-León et al. 2023; Alvarado-Cárdenas et al. 2024a, 2024b). Nowadays, with the new species proposed in this work, Gonolobus comprises 46 accepted species, with ca. 60 % endemics. This contribution reaffirms Mexico as one of the centers of diversity and endemism of the genus ( Alvarado-Cárdenas et al. 2020a, 2020b, 2024a, 2024b; Morillo 2023). Eight species are distributed in the state of Michoacán and ten in Jalisco, three of which are restricted to the state.

Gonolobus uniflorus ( Fig. 4e View FIGURE 4 ) (iNaturalistaMX, 2024f) is a Mexican endemic and a relatively common plant with green flowers widely distributed from Zacatecas to Chiapas, growing sympatrically with several species with restricted distributions and green corollas, such as G. leotzinii , G. grandiflorus (Cav.) Robert Brown ex Schultes (1820: 61) , G. chloranthus Schlechtendal (1834: 520-521) and G. erianthus Decaisne (1844: 592) ( Cervantes 2023). Due to these factors, in addition to the rapid identification of specimens without a detailed review of the important taxonomic characters, it is common for these species to be misidentified as G. uniflorus .

All herbarium specimens of G. leotzinii were identified as G. uniflorus , as well as the observation of iNaturalistaMX (2024). However, G. leotzinii ( Fig. 4c View FIGURE 4 ) (iNaturalistaMX 2024d) differs by its elliptical leaf blade with the apex acuminate (vs. narrowly ovate to ovate, occasionally oblanceolate and with the apex attenuate), sepals 3.48–5.08 mm long, green toward the apex and yellowish-white at the base (vs. 7.5–10.5 mm long and entirely green), corolla lobes 6.54–8.27 mm, ovate with a rounded apex, and a revolute mucro (vs. 1–1.8 cm long, lanceolate to ovate with an acute apex), limb densely pilose and the edge of the faucal annulus is crenate (vs. glabrous limb and entire faucal annulus), and gynostegial corona with cucculate lobes (vs. patent lobes). The set of these morphological differences meets the phenotypic restrictions in the hypothesis established for its proposal as a new species for science.

Other species distributed in the same region with green or yellowish-green corolla and cyathiform gynostegial corona are G. erianthus ( Fig. 4a View FIGURE 4 ; iNaturalistaMX 2024b), G. grandiflorus ( Fig. 4b View FIGURE 4 ; iNaturalistaMX 2024c), G. pancololote (Sessé & Mociño) L.O. Alvarado (2021: 7; Fig. 4g View FIGURE 4 ; iNaturalistaMX 2024e), and G. volcanicus Nuñez Oberg, L.O. Alvarado & S. Islas (2023: 225-231; Fig. 4f View FIGURE 4 ; iNaturalistaMX 2024g) ( Cervantes 2023; Alvarado-Cárdenas et al. 2024a). The flowers of G. erianthus , G. grandiflorus , and G. pancololote are morphologically similar to those of G. leotzinii due to their green rotate corollas and the presence of a fleshy callus, usually white, on the margin of the corolla lobes. In G. erianthus the margins of the corolla lobes are repand, compared to the new species which has flat lobes. The corolla lobes of G. grandiflorus and G. pancololote are lanceolate or elliptical lanceolate (vs. ovate in G. leotzinii ). The faucal annulus of G. leotzinii is inconspicuous and has a crenate edge, unlike G. pancololote where the ring is evident, white, and entire. Other important characteristics that distinguish G. leotzinii from these taxa are the diameter of its flowers (1.5–1.75 cm) and the gynostegial corona with 5 cucculate lobes, whereas in G. erianthus , G. grandiflorus , and G. pancololote the flower diameter is greater than 2 cm and in G. volcanicus is 5.2–7.2 mm (Juárez -Jaimes & Lozada 2003). Likewise, the gynostegial corona in these species has entire and patent lobes ( Table 1).

Identification errors of herbarium specimens are relatively common in diverse groups that share several morphological attributes, as is the case presented here. It is therefore relevant to constantly review the specimens from biological collections. At the same time, we highlight the importance of relying on citizen science platforms such as iNaturalistaMX that enable us to observe attributes that are lost after drying (i.e. color and tridimensional shape). The inclusion of these tools has allowed the identification of new species, new records, new distributional ranges of poorly collected taxa, and an increase of the known distribution area of some species ( Jones et al. 2019; Alvarado-Cárdenas et al. 2020a; Wilson et al. 2020; Callaghan et al. 2022; Chávez-Hernández et al. 2023).