Chamaecrista sempreviva Fort.

Zeferino, Laís Couto, Lewis, Gwilym Peter, Vargas, Wanderleia De, Cândido, Elisa S., Vatanparast, Mohammad, Silva, Marcos José Da, Murashima, Pedro Hiroshi Pereira & Fortuna-Perez, Ana Paula, 2022, A new species of Chamaecrista sect. Absus (Leguminosae, Caesalpinioideae) from Minas Gerais, Brazil, with Notes on Leaf Anatomy, Phytotaxa 536 (3), pp. 252-260 : 253-258

Chamaecrista sempreviva Fort. -Perez & L.C. Zeferino, sp. nov. ( Figs. 1 , 2 , and 4)

Type:— BRAZIL, Minas Gerais: São Gonçalo do Rio Preto, Rio Preto State Park, Atrás da Cachoeira da Sempre Viva , 18°08’32.7” S; 43°20’59.6” W, 784 m a.s.l., 08 June 2014, fl. fr., A. P. Fortuna-Perez, E. S. Cândido & I. Fantini 1594 (holotype BOTU!; isotypes BOTU!, OUPR!) .

Diagnosis:— Chamaecrista sempreviva is morphologically similar to C. monticola ( Bentham [1870: 134) H.S. Irwin & Barneby (1982: 659) and C. catapodia (H.S. Irwin & Barneby [1978: 226–227]) H.S. Irwin & Barneby (1982: 659) in having leaves with one pair of sessile leaflets, but differs by its habit, 4–6 m tall (rarely attaining 2.5 m tall), (vs. up to 1.5 m in C. monticola and C. catapodia ), calyx lobes 18–21 mm long (vs. 9–14 mm long in C. monticola , and 14 mm long in C. catapodia ), and idioblasts in the epidermis of the leaftlets (vs. absent in C. monticola , and in C. catapodia ).

Description:— Shrubs 4–6 m (– 2.5 m) tall, stems erect, conspicuously branched near to the apex. Stems and branches cylindrical villous with white hairs. Stipules 3–5 mm long, linear or lanceolate, apex acute, persistent, hirsute externally. Leaves with two leaflets, sessile, alternate spiral, sub-vertically erect; leaflets 0.5–1.7 × 0.5–1.5 mm, ovate, chartaceous, glabrous to pubescent, apex obtuse to rounded long mucronate (the mucro 3–5 mm long), and cuspidate, base obtuse and asymmetrical, venation brochidodromous, primary and secondary veins impressed on adaxial surface and prominent on abaxial surface, tertiary veins reticulate. Raceme 12–25 cm long, terminal, with 15 to 40 flowers regularly distributed, main axis and pedicel with glandular tector trichomes. Bracts 4–7 mm long, linear to triangular, persistent; bracteoles 2–3 mm long, linear, opposite or alternate, inserted just below the flower, persistent. Flowers 13–22 × 13–25 mm; pedicels 18–25 mm long, cylindrical, with glandular trichomes, ascending in fruit. Sepals 20–21 × 4–6 mm, lanceolate, apex acuminate, chartaceous, red or reddish, setose-viscous and puberulent externally. Petals yellow 5, external 4, 13–20 × 8–11 mm, obovate, the inner fifth petal differentiated, 15–16 × 8–10 mm, coiled, stamens 10, 3– 4 mm long, anthers pubescent long the suture. Pods 20–30 × 7–15 mm, brown, oblong or oblong-falcate, the valves coriaceous, their margin thickened, brown, setose-viscous and puberulent. Seeds 4–5 × 2–3 mm, oblong, black, glossy.

Additional Specimens Examined (Paratypes):— Brazil, Minas Gerais, Couto de Magalhães de Minas, Chapada do Couto , 18º04’18”S, 43º28’15”W, 17 July 1984, fl., A.M. Giulietti et al. CFCR4630 (K, NY, SP, SPF) .

Distribution and Habitat:— Chamaecrista sempreviva is known from only two populations in rocky fields vegetation of the Serra do Espinhaço, Minas Gerais, Brazil. One widespread population occurs in the Rio Preto State Park ( Fig. 3 ), and the other in the Couto de Magalhães de Minas municipality, very close to the Rio Preto State Park.

Conservation Status:— Based on the two known populations, Chamaecrista sempreviva appears to be rare and endemic to the Serra do Espinhaço mountain range in Minas Gerais, growing in rocky fields (“campo rupestre”) of the Cerrado biome. In accordance with the IUCN Red List criteria ( IUCN Standards and Petitions Subcommittee 2017), its conservation status must be considered data deficient (DD) since it is currently known from only two restricted populations. One population is located in the municipality of Couto de Magalhães de Minas, where a new endangered species of Rhynchosia mineira L.M.P. Bezerra & Fort. -Perez (2019: 3), recently was discovered ( Bezerra et al. 2019). The natural habitat there is degraded and includes plantations and pastureland. The other population occurs inside a conservation area (the Rio Preto State Park), which should afford the species some protection. However, the park is in the southern area of the Serra do Espinhaço, and this general area is subject to the threats of agriculture, livestock farming, mining, urban sprawl, tourism and fire ( Pougy et al. 2015; PAN – Serra do Espinhaço Meridional). The species is, therefore, in need of immediate conservation action to prevent further decline of its restricted populations. Recently, a new species Zornia melanocarpa Fort. -Perez (2016: 299) was discovered within this Rio Preto Park ( Fortuna-Perez et al. 2016), further strengthening the need for increased conservation action.

Phenology: — The species was observed in flower and fruit in June and July.

Etymology: — The species epithet refers to the name of one of the most beautiful waterfalls in the Rio Preto State Park, the Cachoeira da Sempre-Viva, the locality of the type of the new species.

Taxonomic Notes: — Chamaecrista sempreviva is characterized by glandular trichomes, densely leafy shrubs with bifoliolate sessile leaves sub-vertically imbricate along the upper stems, amply ovate leaflets which are cordateamplexicaul at the base on the proximal side, and acuminate flower buds and this set of features led us to put it in Chamaecrista sect. Absus subsect. Absus series Unijugae ( Bentham [1870: 134]) H.S. Irwin & Barneby (1982: 659) as cited by Irwin & Barneby (1978, 1982). As the current phylogenetic studies do not admit categories as series in the genus ( Souza et al. 2021), we only suggest the placement of the species in Chamaecrista sect. Absus subsect. Absus .

Although the new species shares with Chamaecrista monticola , C. catapodia , and C. petiolata M. Cota & Rando [2016: 71] (species that were allocated in Chamaecrista sect. Absus subsect. Absus series Unijugae ) the leaves with one pair of leaflets, C. sempreviva is morphologically similar to C. monticola and C. catapodia by characteristics cited in diagnosis. The original description of the species Chamaecrista monticola [≡ Cassia monticola Mart. ex Benth. ] indicates that this species has a very short raceme with few flowers. Analysis of the holotype deposited in Munich Herbarium (M), and material from other herbaria cited in the materials and methods section, allowed us to confirm these inflorescence characteristics (raceme ca. 3 cm long), which differ from Chamaecrista catapodia [≡ Cassia catapodia H.S. Irwin & Barneby ; holotype seen in K and isotype seen in P Herbaria], which has a longer raceme (12–20 cm long) and is multiflorous (> 30 flowers per inflorescence). Chamaecrista sempreviva also has a long raceme (12–25 cm) and is multiflorous (15–35 flowers per inflorescence). Comparative morphological characters of the four species discussed here are presented in Table 1 .

Anatomical Notes: — Our study of the leaflet anatomy of the new species and species that were allocated in series Unijugae ( C. catapodia , C. monticola , and C. petiolata ) revealed the presence of idioblasts in the midrib and mesophyll of Chamaecrista catapodia and C. petiolata ( Fig. 4 G–H, I–J ; Table 2 ). This characteristic was not found in C. monticola or C. sempreviva . In addition, trichomes with a bulbous base (shaggy glandular hairs [ Metcalfe & Chalk 1950; = Cassia ]) were found in Chamaechrista sempreviva , C. monticola , and C. catapodia ( Fig. 4 A–C ; Table 2 ), corroborating results of other anatomical studies showing the presence of secretory structures in the genus (= Cassia ; Solereder 1908; Metcalfe and Chalk 1950). This trichome type was not confirmed in C. petiolata , despite Cota et al. (2016) having noted that it has glandular trichomes on the leaflet surface. Chamaecrista petiolata is unique amongst the four species in having a thick cuticle and a stomatal crest ( Fig. 4 D ; Table 2 ). Secretory idioblasts in the epidermis were observed in C. sempreviva and mucilaginous cells (purple when stained with toluidine blue, in Fig. 4E–F ) are larger than other epidermal cells. These leaflet anatomical analyses have provided new data and taxonomically useful characters for series Unijugae ( Table 2 ).

Figures

FIGURE 1. Chamaecrista sempreviva. A. Habit; B. Detail of leaflet (abaxial surface); C. Detail of leaflet (adaxial surface); D. Apex of leaflet showing long mucro; E. Detail of rachis showing single trichome; F. Detail of pedicel showing trichomes; G. Bract; H. Calyx opened out (outer surface); I. Petals: Median petal, the upper lateral petals, and lower lateral petals; J. Androecium with anthers much longer than the filaments; K. Gynoecium; L. Pod; M. Seed. (all from A.P. Fortuna-Perez et al., 1594). Illustrated by Jesiani Rigon.

FIGURE 2. Chamaecrista sempreviva. A, B, D. Stems showing leaves and, inflorescences; C. Habitat: Cerrado (“campo rupestre”); E. Detail of bifoliolate leaves; F. Flowers. Photos by A.P. Fortuna-Perez.

FIGURE 3. Distribution of Chamaecrista sempreviva. A. Espinhaço Range in Brazil (highlighted in yellow); B. Espinhaço Meridional in Minas Gerais (highlighted in yellow); C. Geographical location of known populations of Chamaecrista sempreviva in Espinhaço Range (cross hatched area: Rio Preto State Park).

FIGURE 4. Anatomical features in species of Chamaecrista series Unijugae. A. Bulbous trichomes in Chamaecrista sempreviva and B–C. C. catapodia; D. Thick cuticle and stomatal crest in C. petiolata; E. Mucilage detected by toluidine blue staining in epidermal cells of C. sempreviva and F. C. monticola; G. Idioblasts in leaflet midrib of C. catapodia; H. Idioblasts in leaflet midrib of C. petiolata; I. Idioblasts in leaflet mesophyll of C. catapodia; J. Idioblasts in mesophyll of C. petiolata.