Colubrina limae Figueira, 2024

Colubrina limae Figueira View in CoL , sp. nov. ( Figures 1 View FIGURE 1 , 2 View FIGURE 2 , and 3)

Type: — BRAZIL. Minas Gerais: Januária, Parque Nacional Cavernas do Peruaçu, trilha para o Arco do André, 15°05’59.9” S, 44°14’19.5” W, 710 m, 28 December 2023 (fr.), M. Figueira, B. Schindler & E. Fazzolino 1977 (holotype UB barcode UB0341122, isotypes BHCB, BHZB, CEN, CESJ, HUEFS, HUFU, IAN, MBM, R, RB, SPF, UFG).

Diagnosis: —The new species is similar to Colubrina elliptica (Sw.) Brizicky & W.L. Stern (1958: 95) , differing by the short petioles <3 mm long (vs. 5–25 mm), brochidodromous venation (vs. eucamptodromous), stipitate glands on, or adjacent to secondary veins on the abaxial face of the leaf (vs. sessile glands on the margin of the leaf blade), fasciculate inflorescence with flower pedicels 6–7.5 mm long (vs. thyrse, 2–4 mm), and fully developed pedicel of mature fruits> 25 mm long (vs. 8–15 mm).

Shrub or treelet up to 5 m tall, stem cylindrical, outer bark brown, thin, a little rough, slightly flexuous branchlets, conspicuously lenticellate, lenticels white in vivo, unarmed, pubescent or sparse pubescent, trichomes reddish-brown or yellowish, erect, internodes 0.4–2.7 cm long. Cataphylls covering the buds, reddish-brown or brown in sicco, abaxial side pubescent along the midrib, caducous. Stipules membranaceous, 5–7 mm long, reddish in sicco, triangular or oblanceolate, convex, adaxial face glabrous, abaxial face pubescent along the median vein, early deciduous, leaving a conspicuous scar on the branch. Petioles (2) 3 mm long, canaliculate, pubescent, trichomes erect, reddish-brown. Leaves alternate, distichous, 3.9–10.5 cm long, 1.9–4.8 cm wide, L:W ratio of 1.3:1 up to 2.8:1, ovate, ovateelliptic, rarely elliptic, membranaceous, margin entire; base subcordate, rounded or obtuse, asymmetrical, with two inconspicuous, glabrous, and yellow glands at the junction with the petiole; apex acute, attenuate or acuminate; adaxial face dull, trichomes restricted to the midrib, abaxial face of young leaves tomentose, becoming pubescent when mature, trichomes erect, golden or reddish-brown, abundant on the midrib and secondary veins; glands on the abaxial face globose, glabrous, stipitate, stalk up to 1 mm long, or sessile, on, or adjacent to the secondary veins, yellow in vivo and yellow or reddish-brown in sicco; veins sulcate on the adaxial face, prominent beneath, 4–6(7) pairs, diverging at an angle between 35° and 70°, leaf venation brochidodromous or festooned brochidodromous, with two veins emerging from the base, secondary spacing irregular, secondary attachment decurrent, intersecondary present, tertiary reticulation irregular. Inflorescence axillary, fasciculate, peduncle absent or very short, up to 1 mm long, (6–)10–20 flowers, long-pedicellate, pedicel 6.0– 7.5 mm long. Flowers yellowish-green (Ratter 2631), 2.5–3 mm long, 1.7–2 mm wide, externally pubescent, trichomes golden, hypanthium infundibuliform, 1–1.5 mm long; sepals 5, deltoid, calyx lobes 1 mm long; petals 5, concave, 1–1.4 mm long, short unguiculate; filament 0.5–0.7 mm long, glabrous, anthers 0.4–0.5 mm long; disk nectariferous 2.2–2.4 mm diam., glabrous, massive, elevated, irregular; ovary 3 (–4)–locular, uniseminate, ovoid, glabrous, style and stigma undifferentiated, trifid, 0.3 mm long, glabrous. Fruit ellipsoid, green, peduncle in full development 25–27 mm long, seed ellipsoid, approximately 5–5.5 x 4–4.5 mm (Anderson 9171).

Comments: —According to its morphological characteristics and geographical distribution, Colubrina limae belongs to Colubrina subgen. Colubrina , which essentially presents South American species with entire leaf blades ( Johnston 1971). On the other hand, C. subgen. Serrataria encompasses species with conspicuously serrate leaf blade margins with glands associated with the teeth that inhabits North America and the Old World. Johnston wrote on the label of the specimen W.R. Anderson et al. 9171 at NY (NY00996164) that it belongs to Colubrina sect. Cowania . We agree with this classification since C. limae has entire leaves and two marginal glands near the base of the blade ( Fig. 1b View FIGURE 1 ), characteristics of C. sect. Cowania . However, it is important to mention that the limits between the sections within C. subg. Colubrina are tenuous and that phylogenetic analyses based on a representative sampling are still required to confirm their monophyly.

In Brazil, Colubrina is so far represented by three species: C. cordifolia Reissek (1861: 98) , C. glandulosa Perkins (1911: 465) and C. retusa (Pittier) R.S. Cowan (1952: 405) , all morphologically distinct and easy to recognize ( Lima et al. 2023). However, these species are easily distinguished from C. limae . Specifically, C. retusa has spines on the branches and conspicuous patelliform glands restricted to the base of the blade, while C. glandulosa has two conspicuous glands at the base of the blade and also submarginal glands, and C. cordifolia has submarginal glands on the blade that turn black when dry ( Tab. 1).

On the other hand, C. limae shares numerous morphological characteristics, especially vegetative ones, with other American species of Colubrina . With C. elliptica , which also belongs to C. section Cowania ( Johnston 1971) , it shares unarmed branches, leaves with similar shape and size, and the entire blade generally pubescent on the abaxial face. However, the two species can still be distinguished by a combination of vegetative and reproductive characteristics and a notable disjunct geographical distribution ( Tab. 1). In addition, C. limae appears to be the only species in the genus to present conspicuous, stipitate glands on, or adjacent to the leaf secondary veins ( Figs. 1c, e View FIGURE 1 ).

Phenology: — C. limae was found in flower in November and in fruit from December to April. The species is probably deciduous during the dry season since the gathering that James Ratter et al. (2631) collected in October has smaller leaves and denser indumentum compared to those in December and April.

Etymology: —The specific epithet is a tribute to the deceased botanist Rita Baltazar de Lima, who dedicated her life to the study of the Brazilian Rhamnaceae and published several taxonomic and floristic papers, as well as a complete revision of all taxa of the family recorded in Brazil ( Lima 2000).

Suggested vernacular name: —During our field expedition, we pointed out the new species to several local guides who were born and raised in the region. Unfortunately, no one recognized C. limae and, consequently, no popular name was registered. C. glandulosa , the species with the largest geographical distribution in Brazil, has several popular names ( Lima et al. 2023), but saguaraji, of indigenous origin, and its variants, are the most common. Here we propose that C. limae be popularly called saguaraji-do-peruaçu in order to raise awareness about conservation of the species and its local environment and to promote scientific communication with the public ( Marinho & Scatigna 2022).

Distribution and habitat: —Species of Colubrina inhabit various types of vegetation, from arid environments with open vegetation to tropical rain forests ( Nesom 2013; Palacios 2015). Some species, such as C. elliptica and C. verrucosa (Urb.) M.C. Johnst. (1963: 93) , are found in rupicolous environments associated with limestone rocks ( Fernández-Nava 1996; Johnston 1971), a habitat similar to that of C. limae . The new species occurs in a small area of the Depressão Cárstica do São Francisco ecoregion, which has unique biophysical characteristics in the transition between Caatinga and Cerrado domains ( Fig. 2 View FIGURE 2 ) and is considered a threatened region ( Sano et al. 2019). The local climate is characterized by strong seasonality with an average annual rainfall of nearly 950 mm ( Stríkis et al. 2024). Some new taxa, including two new genera, have been recently found in this region, making it a promising place for botanical discoveries ( Cardoso et al. 2023; Cheek & Simão‐Bianchini 2013; Lombardi et al. 2005; Nuñez-Florentin et al. 2023).

Colubrina limae was recorded in only two localities in the municipality of Januária , state of Minas Gerais. Based on information on the labels of the collections made in 1972 and 1973, they are situated along Highway BR-479, between 10 and 13 km, west of Januária . Another population, recorded in 2023, is located within the PNCP. All these places are in areas of deciduous dry forest ( Ribeiro & Walter 2008). C. limae inhabits the understory of forests with a continuous canopy ( Fig. 3 View FIGURE 3 ), either on flat or inclined terrain, consisting of shallow soil with limestone outcrops. Based on our field survey in the PNCP, we believe the new species has a gregarious distribution with many individuals in certain places, whereas large areas covered by similar environmental characteristics have no records of the taxon. This disparity could explain the lack of collections over the last 50 years, even with sampling efforts undertaken to record the local flora ( Lombardi et al. 2005). Based on current data, we consider Colubrina limae to be endemic to the northwestern part of Minas Gerais. However, with new collection efforts, we hope to expand the occurrence of this new species to other karst areas around Januária .

Preliminary conservation status:—We classified the species as Data Deficient ( IUCN 2019) because only two populations have been recorded, one of them in a conservation unit. However, this does not mean that the taxon is not threatened. The search for more information, especially occurrence data, is essential for future assessment. It is important to mention that the population along BR-479, which was recorded in the 1970s, was not found during the 2023 expedition. Nonetheless, we found signs of timber extraction and the presence of cattle in the local forest understory. Finally, the region is facing the impacts of severe climate change driven by anthropogenic forces and characterized by a sharp decrease in rainfall and increase in temperature ( Stríkis et al. 2024).

Additional specimens examined: — BRAZIL. Minas Gerais: Januária , approx. 10 km W of Januária , 15°30’ S, 44°30’ W, 20 October 1972 (fl.), J. Ratter, S.G. da Fonseca & R.A. Castro 2631 (E barcode E00828064, NY barcode NY02211495, P barcode P06765153, UB); 13 km by road W of Januária on road to Serra das Araras, ca. 2 km E of large limestone hill, 575 m, 19 April 1973 (fr.), W. R. Anderson et al. 9171 (CM barcode CM346232, NY barcode NY00996164); Parque Nacional Cavernas do Peruaçu, próxima da trilha do Arco do André, 15º06’01” S, 44º14’19” W, 710 m, 28 December 2023 (fr.), B. Schindler, M. Figueira & E. Fazzolino 571 (CEN, RB, UB); Parque Nacional Cavernas do Peruaçu, trilha para Lapa Bonita, 15°06’25” S, 44°14’23” W, 650 m, 28 December 2023 (fr.), M. Figueira, B. Schindler & E. Fazzolino 1973 (CEN, RB, UB).