Chamaecrista petiolata M. Cota & Rando, 2016

Cota, Matheus Martins Teixeira, Rando, Juliana Gastaldello & Mello-Silva, Renato, 2016, Chamaecrista petiolata (Leguminosae, Caesalpinioideae), new species from Diamantina Plateau, Minas Gerais, Brazil, Phytotaxa 267 (1), pp. 70-76 : 71-73

Chamaecrista petiolata M. Cota & Rando , sp. nov. ( Figs. 1 , 2 )

Chamaecrista petiolata mostly resembles C. catapodia and C. monticola but differs in the habit and leaves. Chamaecrista catapodia and C. monticola are prostrate to erect shrubs, the stem-axis exceeding 1.5 m with sessile leaves. Chamaecrista petiolata is a subshrub not exceeding 40 cm, with petiolate leaves. Chamaecrista petiolata show yellow glandular, bulbous hairs in lamina of leaflets, whereas C. catapodia and C. monticola show glandular, bulbous hairs in the leaflets margins only. Moreover, the leaflets are elliptic to rotund in C. petiolata , and obliquely ovate-oblong in C. catapodia and ovate in C. monticola .

Type: — BRAZIL. Minas Gerais: Diamantina, estrada Conselheiro Mata—Diamantina, km 166, 23 February 1986, (fl), R. Mello-Silva et al. CFCR 9546 (holotype SPF!, isotypes DIAM!, K, MBM!, NY!, UEC!).

Subshrub with xylopodium, erect, up to 40 cm alt., branches, stipules, leaves, inflorescence axis, bracts, bracteoles and abaxial face of sepals with yellow glandular-bulbous hairs and white villus; leaves bifoliolate; stipules persistent, subulate; petiole 3–9 mm long, sulcate; rachis 1–2 mm long; leaflet blades 0.9–2.1 × 0.65–1.75 cm, rotund to elliptic, the apex rounded to slightly retuse, shortly mucronate from the excurrent mibrid, the base rounded or oblique, venation reticulate. Inflorescence simple racemose, terminal bracteolate, 4–12-flowered; pedicel 8–11 mm long; bracts triangular to subulate, 3–4 mm long; bracteoles triangular, 1,5–2,5 mm long; sepals elliptic-acute, orange, 1.1–1.3 cm long; external petals, 4, obovate, cuneate, 1.3–1.6 cm long, yellow, internal petal differentiated, ca. 1.35 cm long, yellow; stamens 10, 4–6 mm long, filaments glabrous, anthers papillate, puberulous along the sutures; ovary 4–5 mm long, style and stigma 7–9.5 mm long. Fruit and seeds not observed.

Additional specimens examined: — BRAZIL. Minas Gerais:Diamantina,estrada Conselheiro Mata—Diamantina, km 166, 12 January 2012, (fl), J. G. Rando & A. Nogueira 1149 ( SPF) ; Rodovia Diamantina-Conselheiro Mata ( MG 220 ), cerca de 10 km de Conselheiro Mata, 24 February 2015, (fl), M. M. T. Cota, L.P. Canuto, P. Miyagawa, C.S. Paula & A. L. Braga 820 ( SPF) .

Distribution: — Chamaecrista petiolata is only known from two points of the dirt road from Diamantina to the district of Conselheiro Mata, in Minas Gerais state, Brazil ( Fig. 3 ).

Phenology: —The species was observed with flowers in January and February. Fruits and seeds have not been found.

Etymology: —The specific epithet refers to the 3 to 9 mm long petiole of C. petiolata , in contrast with the sessile leaves of C. catapodia and C. monticola .

Conservation Status: — Chamaecrista petiolata is represented by only three collections from the same unique locality in Diamantina plateau , which is subject to human disturbance due to tourism, and accidental fires. The extent of occurrence cannot be calculated because the minimal number of three recorded points is not available. The estimated occupancy area is 8000 km 2 ( Fig. 3 ). Therefore it can be considered a critically endangered species according to IUCN (2014) criteria.

Discussion: — Chamaecrista petiolata is characterized by small and erect subshrub habit, glandular-pubescent indument, bifoliolate and peciolate leaves, elliptical to rotunded leaflets, congested racemes with 4–12 flowers, and elliptic-acute sepals. It resembles C. catapodia and C. monticola in the bifoliolate leaves, in the glandular-pubescent indument and in the simple racemose inflorescence, and the type specimen at NY bears a note from Rupert Barneby assigning it as a possible new variety of C. monticola . However, these species are shrubs exceeding 1.5 m in height or length, much taller or longer than C. petiolata , and show sessile leaves. Chamaecrista cotinifolia ( Don 1832: 445) Irwin & Barneby (1982: 658) , C. echinocarpa ( Bentham 1870: 136) Irwin & Barneby (1982: 659) , and C. kirkbridei ( Irwin & Barneby 1978: 212) Irwin & Barneby (1982: 659) are also bifoliolate species with petiolate leaves and glandular-bulbous hairs that are sympatric with C. petiolata . Nonetheless C. kirkbridei and C. echinocarpa are shrubs exceeding 1.5 m in height, with obovate leaflets, and C. cotinifolia is a decumbent subshrub with glabrous branches, orbicular leaflets and obovate sepals. During four years of botanical exploration in the Diamantina Plateau and other nearby mountain ranges, we have never found this species in other places nor in vegetative stage. Chamaecrista petiolata would belong to sect. Absus subsect. Absus ser. Unijugae ( Bentham 1870: 134) Irwin & Barneby (1982: 659) due to the glandular-pubescent indument, the absence of extrafloral nectaries, the simple racemose inflorescence, and the bifoliolate leaves.

Key to the species of the ser. Unijugae in the Diamantina Plateau , Minas Gerais

1. Bi–many–foliolate leaves, margin of leaflets plane or revolute, indument variable, if glandular-pubescent, the trichomes are not white villus with glandular-bulbous hairs, and/or the leaves are more than bifoliolate with revolute margins................................... ...................................................................................................................... other Chamaecrista from the Diamantina Plateau, MG

1. Bifoliolate leaves, margin of leaflets plane, indument glandular-pubescent or white villus with glandular-bulbous hairs................. ........................................................................................................................ Chamecrista sect. Absus subsect. Absus ser. Unijugae

2. Erect subshrubs up to 40 cm alt., leaves petiolate............................................................................................................. C. petiolata

2. Prostrate to erect shrubs more than 1.5 m long, leaves sessile

3. Leaflets obliquely oblong-ovate, lamina glandular-pubescent, raceme more than 8 cm long, with over than 25 flowers, pedicels 10–13(–15) mm long, refracted in fructification............................................................................................................. C. catapodia

3. Leaflets ovate, lamina glabrous with glandular-pubescent margins, raceme up to 5 cm long, with 5–15 flowers, pedicels (16–) 19– 21 mm long, ascending in fructification.......................................................................................................................... C. monticola

Figures

FIGURE 1. Chamaecrista petiolata. A. Flowering branch. B. Leaflet. C. Detail of leaflet, showing indument on upper surface. D. Flower. E. Sepals. F. Stamen. G. Detail of stamen, showing the apical pore in the anthers. H. Gynoecium. I. Detail of gynoecium, showing the stigma. Drawn from Rando 1149 (SPF) by Carla de Lima.

FIGURE 2. Chamaecrista petiolata. A. Habit. B. Flowering branch. C. Flowering branch showing inflorescence. D. Flower, showing the internal petal differentiated. (A. photo from Cota 820 by P. Miyagawa; B–D. photo from Rando 1149 by A. Nogueira).

FIGURE 3. Distribution map of Chamaecrista petiolata, showing occupancy area.