Taxonomy

Stenanona morenoi Ortíz-Rodr. & Moreno-Méndez, sp. nov., Figs. 1-3.

Figure 1: Stenanona morenoi Ortíz-Rodr. & Moreno-Méndez. A. branchlet; B. inflorescences borne on leafless portions of branches; C. velvety fruit Surface; D. fruit inside; E. seed. Drawn by Lizbeth Pérez Lucas from the type (A) and from G. Moreno Méndez 177 (B-E). 

Figure 2: Photos of Stenanona morenoi Ortíz-Rodr. & Moreno-Méndez in vivo. A. habit; B. bark; C. branchlet; D. inflorescences and flowers (note the red blotch at the base inside); E. inflorescences borne on leafless portions of branches; F. young fruits borne on leafless portions of branches; G. velvety fruit. Photos by Gaspar Moreno-Méndez. 

Figure 3: Distribution of Stenanona morenoi Ortíz-Rodr. & Moreno-Méndez, Stenanona migueliana Ortíz-Rodr. & G.E. Schatz, Stenanona stenopetala (Donn. Sm.) G.E. Schatz and Stenanona zoque Ortíz-Rodr. & Gómez-Domínguez, based on georeferenced localities available at the Global Biodiversity Information Facility (^{GBIF. 2019a}; ^{GBIF. 2019b}) and supplemented with field records. 

TYPE: MEXICO. Chiapas, municipio Chilón, ejido San Jerónimo, 1.42 km al sur de la comunidad Jol Cacuala, camino al predio de Don Jerónimo Moreno, 1520 m, 17°03'04"N, 92°04'35"W, 03.VII.2019, G. Moreno Méndez 87 (holotype: HEM!, isotypes: MEXU!, MO!, NY!).

Stenanona morenoi is similar to S. migueliana Ortíz-Rodr. & G.E. Schatz, S. stenopetala (Donn. Sm.) G.E. Schatz and S. zoque Ortíz-Rodr. & Gómez-Domínguez, but it can be distinguished from these three species by the combination of 2 or 4-flowered inflorescences, partially fused sepals, cream to light yellow flowers with a red blotch at the base of the inner petals, numerous ovules per carpel and surface of the monocarps completely covered with short, golden-brown, erect hairs, resulting in a velvety texture.

Trees 10-20 m tall, 28 cm diameter; young twigs, buds and petiole densely covered with appressed, golden-brown hairs; leaves distichous, oblong-elliptic, chartaceous, punctate with minute lens-like warts, 8-24 cm long, 3-8 cm broad, base obtuse to acute, apex acute to short acuminate, margins slightly revolute, upper side of leaves shiny and glabrous, lower side of leaves very sparsely covered with appressed, golden-brown hairs to glabrous; venation weakly brochidodromous with 8-14 lateral veins/side, midrib impressed above, raised below, densely covered with appressed hairs; petiole 5-10 mm long, ~2 mm diameter, canaliculate; inflorescence borne on leafless portions of old branches (ramiflory), 2 or 4-flowered, pedicels and outer side of bracts densely to rather densely covered with appressed and erect, golden-brown hairs; peduncles minute; pedicels arise from a condensed short shoot, 18-45 mm long, 2-2.5 mm diameter in vivo (1-1.5 in sicco, up to 3 mm diameter in fruit), pendent, with a tiny basal bract; sepals 3, partially fused at the base, broadly ovate, 2-3 mm long, 2-3 mm broad, base truncate, apex acute, externally densely covered with golden-brown appressed hairs, sparsely covered with golden-brown appressed hairs inside, sepals persistent in young fruits; petals 6, free, linear to linear-triangular, in two sub-equal whorls, cream to light yellow at anthesis with a red blotch at the base of the inner petals, 23-60 mm long, 1-3 mm broad, base rounded to truncate, apex acute to aristate, densely covered with golden-brown appressed hairs externally, sparsely covered with golden-brown appressed hairs to glabrous inside; stamens ~80, 1.2-1.8 mm long, apical part of connective expanded above the thecae, truncate discoid or slightly prolonged toward the gynoecium, sparsely covered with erect golden-brown hairs; carpels 3-6, ~2.5 mm long, stigma globose to reniform, ovary prismatic to pear-shaped, densely covered with appressed and erect golden-brown appressed hairs, ovules 9-12, uniseriate; monocarps 1-4, globose to ellipsoid, 55-60 mm long, 45-50 mm broad, surface completely covered with short golden-brown erect hairs (velvety), stipes 4-6 mm long, ca. 10 mm diameter, fleshy mesocarp, granular when dry; seeds 6-8, wedge-shaped to depressed globose, 22-25 × 12-14 ×7-11 mm.

Etymology: the specific epithet honors Manuel Moreno Demeza for his extraordinary work in favor of forest conservation in northern Chiapas.

Distribution and ecology: the species is only known from the karstic type locality in the highlands of northern Chiapas (more than 1000 m a.s.l., Fig. 3), where contrary to other karstic regions of southern Mexico, organic matter in the soil is very abundant and covers large part of the limestone rocks. Stenanona morenoi is part of the upper strata and is associated with species as Quercus paxtalensis C.H. Mull., Garcinia intermedia (Pittier) Hammel, Quararibea funebris (La Llave) Vischer, and Guarea glabra Vahl. Frequently the stems of S. morenoi are so long that they lie on other trees for support (also observed in S. stenopetala but not in other species of Stenanona). During the morning, the flowers of S. morenoi release a fruity aroma, but no flower visitors were observed.

Conservation status: We currently lack the necessary information to assess definitively the conservation status of Stenanona morenoi. However, according to the criteria established by the IUCN (2011), it is possible to tentatively determine that the species is Critically Endangered (CR B1ab (iii)). Its estimated area of occupancy (AOO) is 8 km² and extent of occurrence (EOO) is 0 km². Although it is likely that the small number of georeferenced data results in an underestimation of its EOO, at the type locality the species was found into two nearby patches of forest isolated from each other by corn crops. Furthermore, the species appears to be extremely rare. In one of the patches only five individuals were counted, while in the other site only eight were observed.

Additional specimens examined: MEXICO. Chiapas, municipio Chilón, ejido San Jerónimo, 1.42 km al sur de la comunidad Jol Cacuala, camino al predio de Don Jerónimo Moreno, 1360 m, 17°03'35"N, 92°06'09"W, 09.VII.2019, G. Moreno Méndez 177 (HEM, MEXU).

Extraordinary plants and where to find them

Based on its general floral morphology, Stenanona morenoi is placed within subclade A of the Desmopsis-Stenanona clade (^{Ortiz-Rodriguez et al., 2018}a). Within this lineage, S. morenoi is related to Stenanona migueliana, S. stenopetala and S. zoque (here named the Stenanona stenopetala group, Table 1). The four species are medium to large sized trees (7-25 m tall) and share the cauliflorous/ramiflorous inflorescences and the long-pedicellate flowers with six free, sub-equal, linear to linear-triangular petals (^{Ortiz-Rodriguez et al., 2014}; ^2018b). These shared characteristics (synapomorphies) among the members of the Stenanona stenopetala group contrast with those present in the type species of the genus (^{Standley, 1929}; ^{Fries, 1931}), with which they are not phylogenetically related (^{Ortiz-Rodriguez et al., 2016}; ^2018a). The type species, Stenanona panamensis Standl., is a small sized tree with short pedicellate flowers, partially fused petals and long sepals with obvious venation in vivo, none of these features shared with members of the Stenanona stenopetala group (^{Schatz and Maas, 2010}; ^{Ortiz-Rodriguez et al., 2014}; ^2018b). Members of this group are distributed in the north of Mesoamerica and are restricted to the karst areas of the region. The four species have a very restricted distribution range and occur allopatrically (^{Ortiz-Rodriguez et al., 2018b}, Fig. 3). Within the genus Stenanona the species distributed in Guatemala and Mexico occur within this biome and tend to be phylogenetically related (^{Ortiz-Rodriguez et al., 2016}; ^2018a), and based on their different levels of morphological and genetic variation, it is possible to hypothesize that karst areas have played a very important role in the evolutionary history of this genus in Mesoamerica.

Among the members of the group, S. morenoi is well differentiated based on its vegetative and reproductive characteristics (^{Ortiz-Rodriguez et al., 2018b}; Figs. 1, 2, Table 1). The partially fused sepals of S. morenoi are not shared with other species of the Stenanona stenopetala group, but are common in other species of Stenanona such as S. carrillensis G.E. Schatz & Maas, S. cauliflora (J.W. Walker) G.E. Schatz and S. hondurensis G.E. Schatz, F.G. Coe & Maas (here named the Stenanona cauliflora group). However, members of the Stenanona cauliflora group are invariably tetramerous and have many carpels with few ovules each (^{Schatz and Maas, 2010}). Interestingly, fruits characteristics of S. morenoi (Figs. 1, 2) are absent in the other species of Stenanona (^{Schatz and Maas, 2010}). Its velvety fruits are rather similar to those present in some species of Sapranthus Seem. (^{Schatz et al., 2018}) and in Tridimeris hahniana Baill., but its floral characteristics are very different from those of these genera.

Besides the features mentioned, another attribute that distinguishes S. morenoi from its congeners is its distribution at higher altitudes. The new species inhabits within a tropical karst forest between 1300 and 1500 m a.s.l., while most species of Stenanona occur between 200 and 1000 m a.s.l. (^{Schatz and Maas, 2010}; ^{Ortiz-Rodriguez et al., 2014}, ^2018b).