Gonolobus espejoi, a new species from Veracruz, Mexico, is described and illustrated. The new taxon shares characteristics with G. albiflorus and G. spiranthus such as the presence of a stipitate gynostegium, but differs from these species by having campanulate corolla, corolla lobes with two lateral purple calluses with the right margin ciliate, oblong-spatulate anther appendages, and a cotyliform style apex. A comparative table and a distribution map of the new taxon and the morphologically similar species is provided.
The New World genus Gonolobus Michx. (Gonolobinae) includes about 150 species distributed from the southern United States to Argentina (Krings et al. 2008; Stevens 2009). The genus has been recovered as monophyletic and it is recognized by the presence of laminar dorsal anther appendages, although these are lacking in G. denticulatus (Vahl) W.D.Stevens and allies (Krings et al. 2008; Morillo 2015; Mangelsdorff et al. 2016; McDonnell et al. 2018). Another important character to recognize Gonolobus are follicles with an asymmetrical base borne at 0–90°from the pedicel (Stevens 2005; Krings et al. 2008). In Mexico, Gonolobus includes 38 species, of which 18 are endemic to the country (Alvarado-Cárdenas et al. 2020).
During the curation of the Apocynaceae collection of the Herbario Metropolitano, Universidad Autónoma Metropolitana Iztapalapa (UAMIZ), material from a species of Gonolobus (A. Espejo y A. R. López Ferrari 4441) could not be assigned to any known species (Stevens 2001; Stevens 2009). Subsequent to additional work in pertinent herbaria i.e. Herbario Nacional (MEXU), Instituto de Botánica (IBUG), and Instituto de Ecología AC (XAL) (Thiers 2020), we here recognize the material as belonging to a novel species.
Materials and Methods
A stereoscopic microscope (Leica EZ4 HD) was used to measure the flower parts and to take pictures, mainly of the pollinarium. Later the images of the pollinarium were measured with the ImageJ software (Abràmoff et al. 2004). A morphological description was made based on the terminology of Stevens (2009). A comparative table of the morphologically similar species was prepared based on the herbarium specimens and protologues of Gonolobus albiflorus W.D.Stevens and G. spiranthus Juárez-Jaimes, W.D.Stevens & Lozada (Stevens 2005; Juárez-Jaimes et al. 2009). With the information obtained from the herbarium specimen labels, a distribution map of the three species was made with the QGIS 2.18 program (QGIS Development Team 2020) using the layers of “División política estatal” and the digital elevation model of Mexico, to represent the main elevations of the country (Guevara and Arroyo-Cruz 2016; INEGI 2019).
Gonolobus espejoi G.M.Hernández-Barón, Hern.-Barón et López-Ferr., sp. nov. Type: México. Veracruz: Xico, cascada de Texolo, más o menos 2–3 km al S de Xico, 19°24′50″N, 96°59′39.2″W, 1200 m, 5 May 1991, A. Espejoy A. R. López Fer-rari 4441 (Holotype: UAMIZ!, Isotypes: MEXU, XAL)
Gonolobus espejoi is similar to G. albiflorus and G. spiranthus but exhibits campanulate corollas, corolla lobes with two lateral purple calluses and ciliated right margins, oblong-spatulate anther appendages, and cotyliform style apex.
Twining vines, white latex present. Stems cylindrical with mixed indumentum, long eglandular trichomes, 2–3 mm long, multicellular, yellow with dark septa and short glandular trichomes, ca. 0.2 mm long, uniformly arranged on the stem. Leaves opposite; stipular colleters absent, petioles 3.5–5 cm, with the same type of indumentum present on the stem; leaf blades ovate to widely ovate, (6–)8.1–10.9 × (3–)4.5–6.7 cm, apex acuminate, base cordate, lobes diverging or converging, sinus 0.68–1.3 cm deep, abaxially pilose with trichomes of 1.05–2.3 mm, adaxially pilose with appressed trichomes, 0.8–2.33 mm long, mixed indumenta on the midvein, 7–10 pairs of lateral veins, colleters 5–7, adaxially, at the base of the main veins. Inflorescences extra-axillary, one per node, racemiform, quite contracted, with 6–11 flowers, indumentum mixed, peduncles 3.7–5.0 cm, floral bracts linear, 1.1–1.5 mm, pilose. Flowers pedicellate, pedicels 1.6–3.2 cm; calyx lobes divided almost to the base, narrowly lanceolate, 5.12–6.36 × 1.44–1.80 mm, tube 1.2–2 mm long, apex acute, reflexed, abaxially pilose, purple at their distal portion, completely purple adaxially, glabrous, colleters one per sinus; corolla campanulate, with the base slightly inflated or crateriform, greenish, aestivation contorted and dextrorse, faucal annulus a continuous ring, 0.2–0.4 mm, sinuate, glabrous, located below the sinuses of the corolla lobes, corolla tube 2–3.5 mm, glabrous, lobes narrowly lanceolate, 8.9–11.5 × 2.20–2.98 mm, acute, coiled and reflexed, margins purple, thickened adaxially, right margin ciliated and the left one glabrous, abaxially pilose, adaxially glabrous; gynostegium 3.03–5.27 × 1.1–3.50 mm, with stipe, stipe with 5 ribs, 2.03–3.31 × 0.86–1.26 mm, each rib with a narrow tooth near the apex, ca. 0.5 mm long, located below the anther appendages, slightly widened at the base, corona lobes 5, glabrous, 1.53–2 × 1.25–1.37 mm long, cup-shaped, fleshy, each lobe papillose abaxially with inconspicuous central thickening adaxially, the lobes fused basally forming a small ring, adnate to the base of the gynostegium and completely to the corolla; dorsal anther appendages 2.20–2.54 × 1.01–1.35 mm, oblong-spatulate, fleshy, deflexed, terminal appendages of anthers hyaline, broadly ovate, 0.28–0.41 × 1.8–2 mm; corpusculum ovoid, 0.16–0.24 × 0.05–0.1 mm, brown, caudicle 0.13–0.19 × 0.11–0.13 mm, flat; pollinia ovoid, slightly horizontal, 0.77–1.11 × 0.27–0.37 mm, excavated and translucent at their junction with the caudicles; style concave, apex cotyliform, slightly ascending with the margin slightly crenate, 0.4–0.5 × 0.6–0.7 mm at the highest ends. Follicles unknown. Figures 1–2.
Distribution and Habitat—Gonolobus espejoi is known from the surroundings of the Texolo waterfall, in the municipality of Xico, located in the state of Veracruz. It grows in secondary vegetation derived from the deciduous tropical forest at an elevation of 1200 m. There are two species with which it shares morphological characteristics: Gonolobus albiflorus which grows in the surroundings of the Nevado de Colima, within the limits of Jalisco and Colima at elevations between 2000 and 2100 m, and G. spiranthus which is distributed in the states of Guerrero, Jalisco, Michoacán, and Oaxaca, at elevations of 220 to 1500 m. As far as is known, the three species are allopatric in distribution (Fig. 3).
Phenology—The species is flowering in May.
Etymology—The specific epithet honors Dr. Mario Adolfo Espejo Serna, who collected specimens of this species during his expeditions to the state of Veracruz. Dr. Espejo is a distinguished Mexican botanist, a specialist in monocotyledons of Mexico, mainly from the Bromeliaceae and Orchidaceae families. He has dedicated his academic life to the study of botany and teaching, at the Universidad Autónoma Metropolitana Iztapalapa. Dr. Espejo is a professor committed to teaching, and also has great human qualities. For this reason, we decided to name this plant in his honor as a recognition of the passion and enthusiasm he shares for plants, which he has managed to transmit to students, who will be part of the new generations of botanists.
Conservation Status—As Gonolobus espejoi is currently known only from the type locality, we consider it Data Deficient (DD) (IUCN 2012).
Notes—Gonolobus espejoi is morphologically similar to G. albiflorus and G. spiranthus because the three species exhibit a gynostegium with a conspicuous stipe. With G. albiflorus it shares a stipe and reflexed corolla lobes. However, G. albiflorus has a prominently 5-winged stipe, erect calyx lobes, tubular and white corollas, and spatulate and concave dorsal anther appendages on the adaxial surface, whereas G. espejoi has a stipe with 5 ribs, reflexed calyx lobes, campanulate green corollas with a short tube, and anther appendages oblong-spatulate and flat on the adaxial surface.
Gonolobus espejoi and G. spiranthus present green corollas and a well-developed stipe. Gonolobus spiranthus has a cylindrical stipe, erect calyx lobes, strongly spiral and erect corolla lobes as well as sagittate-triangular anther appendages; while G. espejoi has a stipe with 5 ribs with a tooth near the apex, reflexed calyx and corolla lobes, and oblong-spatulate anther appendages (Table 1). Some morphological characters of Gonolobus espejoi, such as corolla lobes with two purple callus margins with the right margins ciliated, and the style apex cotyliform, are novel characters within the genus.
Mexico is a center of diversity for Gonolobus, with about one-third of its species distributed in the country (Stevens 2005; Juárez-Jaimes et al. 2009). With the new taxon here described, the number of species of Gonolobus endemic to Mexico reaches 19. Gonolobus espejoi appears to be endemic to the Xico region, in Veracruz, but we cannot discount that its distribution may be wider. Likewise, it is likely that other novelties in the genus Gonolobus will be discovered.
Comparative characters of Gonolobus espejoi, G. albiflorus, and G. spiranthus.
We thank: 1) the curators of the cited herbaria for the facilities provided for the revision of the material; 2) M. en C. Verónica Juárez Jaimes for her critical comments that helped to improve the manuscript, 3) Ericka Belén Cortez for the illustration of the new species, and 4) the two anonymous reviewers for the valuable comments that helped to improve the manuscript.
GMHB, LJHB, and ARLF drafted the manuscript, measured and compared the specimens, elaborated the description, and produced the comparative table. GMHB had primary responsibilities for the species identification, herbarium specimens review, and elaboration of the figures.