Chamaecrista sect. Absus (Collad.) Irwin & Barneby (1982: 664) emend. A.O. Souza, G.P. Lewis & M.J. Silva (2021: 386) subsect. Absus

Souza, Alessandro Oliveira De, Cavalcante, Raphael Guarda & Silva, Marcos José Da, 2022, Taxonomic revision of Chamaecrista sect. Absus subsect. Absus (Leguminosae, Caesalpinioideae) with adjustments in the new classification, Phytotaxa 565 (1), pp. 1-82 : 4-6

Chamaecrista sect. Absus (Collad.) Irwin & Barneby (1982: 664) emend. A.O. Souza, G.P. Lewis & M.J. Silva (2021: 386) subsect. Absus

≡ Cassia sect. Absus Colladon (1816: 184) .

— Type species: Chamaecrista hispidula (Vahl) Irwin & Barneby.

= Grimaldia Schrank (1805: 184) . Type species:— Chamaecrista absus .

= Chamaecrista ser. Absoideae ( Bentham 1870: 131) Irwin & Barneby (1982: 660) ≡ Cassia ser. Absoideae Bentham (1870: 131) . Type species:— Chamaecrista hispidula ( Vahl 1807: 10) Irwin & Barneby (1982: 661) .

= Chamaecrista ser. Oligospermae ( Irwin & Barneby 1978: 38) Irwin & Barneby (1982: 648) ≡ Cassia ser. Oligospermae Irwin & Barneby (1978: 38) . Type species:— Chamaecrista oligosperma ( Bentham 1870: 147) Irwin & Barneby (1982: 648) .

Shrubs erect with straight, drooping or supporting branches. Subshrubs erect, prostrate or decumbent. Herbs only in individuals of Ch. absus . Indumentum of branches, leaves or at least the inflorescence composed of mix of tector and glandular trichomes, rarely glabrous or glabrescent. Stipules persistent, linear, lanceolate or elliptic, glabrous or with the same indumentum of the branches. Leaves petiolate, paripinnate, alternate-distichous or alternate and spirally arranged, with 2 pairs of leaflets, the distal pair being slightly larger than the proximal pair, leaves with (6)7–18 pairs of leaflets only in Ch. oligosperma . Extrafloral nectary absent. Racemes terminal or axillary, corymbiform or not, or rarely panicles, erect or pendulous, lax or congested. Flowers dichlamydeous, pentamerous, asymmetrical, aposepalous and apopetalous, a pair of bracteoles on the pedicel; sepals isomorphic, glabrous or with indumentum, yellowish-green with or without reddish or vinaceous macules; petals yellow, orange or reddish, 3 adaxial isomorphic and one of the abaxial petals falcate-curled and encircling with the stamens (except in Ch. absus ); androecium with 10 stamens or (2–) 3–7 in Ch. absus , isomorphic, stamens with anthers basifixed longer than filaments, dehiscence apical poricidal and pubescent laterally; gynoecium glabrous or with indumentum, ovary oblongoid, dorsoventrally flat, sessile, with a curved style in the upper third and punctiform stigma covered by a crown of trichomes. Legume oblong or linear-oblong, dorsoventrally flat and elastically dehiscent, with coriaceous or chartaceous valves, brown, reddish or yellowish-green, glabrous or with indumentum. Seeds (1–)4–8, rhomboid, ovoid or obovoid, light brown or dark or blackish, usually glossy.

Chamaecrista sect. Absus subsect. Absus , as defined herein, comprises 18 species predominantly Neotropical with 12 species endemics of Brazil. Chamaecrista absus is the only species that has a pantropical distribution. The species grow on plains or mountains areas, between 50 and 1500 meters in altitude, usually associated with open areas of seasonally dry vegetation such as cerrado, caatinga and rupestrian fields, but can also be found near areas of forests, restingas and disturbed environments.

Regarding conservation, of the recognized species, 15 were classified as Least Concern (LC), one as Vulnerable (VU), one as Endangered (EN), and one as Data Deficient (DD) , according to each species comment.

In taxonomic terms we propose: i) a new combination of Ch. viscosa var. major that is now recognized as a species ( Ch. major ), ii) nine synonymizations: Ch. absus var. meonandra ( Irwin & Barneby 1978: 282) Irwin & Barneby (1982: 664) under Ch. absus ; Ch. acosmifolia var. euryloba , Ch. acosmifolia var. oropedii and Ch. verruculosa Fernandes & Nunes (2000: 2) under Ch. acosmifolia ; Ch. brevicalyx var. elliptica ( Irwin & Barneby 1978: 252) Irwin & Barneby (1982: 660) under Ch. brevicalyx ( Bentham 1870: 134) Irwin & Barneby (1982: 660) ; Ch. fagonioides var. macrocalyx Irwin & Barneby 1978: 276 ) Irwin & Barneby (1982: 661) and Ch. punctulata ( Hooker & Arnott 1840: 420) Irwin & Barneby (1982: 661) under Ch. fagonioides ; Ch. conferta var. gurgueiana under Ch. juruenensis ( Hoehne 1922: 13) Irwin & Barneby (1982: 660) and Ch. viscosa var. paraguayensis under Ch. viscosa ; and, iii) two lectotypifications and six new records. Explanations of our decisions follow in the comments of each taxon.

Most members of Ch. sect. Absus subsect. Absus share the leaves with two pairs of membranous or papyraceous leaflets, the distal pair slightly larger than the proximal one, terminal or axillary inflorescences and flowers with yellow or orange petals, with few exceptions. In general, the studied species are easily recognizable due to their peculiar morphologies and can be differentiated by the following key:

Key to species of Chamaecrista sect. Absus subsect. Absus

1. Leaves with (6)7–18 pairs of leaflets; legumes with 1 or 2(3) seeds ................................................................ 16. Ch. oligosperma

- Leaves with 2 pairs of leaflets; legumes with 4–8 seeds .................................................................................................................. 2

2. Leaves alternate distichous with leafy appendix inter-petiolule; flowers 5–9 mm long with 5 flat petals, the inner one slightly falcate, but not curled and nor encircling the stamens; androecium with (2)3–6(7) stamens; style 1.3–3 mm long; root nodules present............................................................................................................................................................................. 1. Ch. absus

- Leaves alternate spiral without leafy appendix inter-petiolule; flowers 1.2–4.5 cm long with 4 flat petals and 1 inner one falcatecurled and encircling part of the stamens; androecium with 10 stamens; styles 8–22 mm long; root nodules absent or unknown .... ........................................................................................................................................................................................................... 3

3. Leaves ascending; leaflets linear-oblong or oblanceolate 2.5–4 times longer than wide; stipules 1.5–2.5 mm wide, elliptic or oblanceolate, rarely lanceolate; inflorescence congested corymb.......................................................................... 4. Ch. anamariae

- Leaves plagiotropic or slightly ascending; leaflets elliptic, oboval, oval, spatulate, obcordate or suborbiculares, 0.5–2 times longer than wide; stipules linear or lanceolate 0.3–0.5 mm wide; inflorescence lax raceme or panicle...................................................... 4

4. Stem or branches with exfoliating bark; young branches whitish or pale yellowish; petiole 3–7.5 cm long .................................. 5

- Stem or branches without exfoliating bark; young branches greenish, yellowish, light or dark brown; petiole 0.5–3.5 cm long .. 6

5. Leaflets 4.5–9.3 cm long, discolor, margin revolute; stamens barbulate ................................................................... 5. Ch. barbata

- Leaflets 1.5–4.5 cm long, concolor, margin flat; stamens not barbulate ................................................................ 6. Ch. brevicalyx

6. Erect shrubs 1.5–3.5 m tall; several axillary racemes at the end of the branches in panicle aspect ................................................. 7

- Erect, decumbent or creeping subshrubs 0.2–1.5 m tall, rarely erect shrub 3 m tall (individuals of Ch. juruenensis ); solitary and terminal racemes, rarely axillary ...................................................................................................................................................... 9

7. Stem with supporting or hanging branches; leaflets discolor, the upper surface dark green, the lower surface dull green; petals suborbicular or widely oboval .............................................................................................................................. 2. Ch. acosmifolia

- Stem with erect branches; leaflet concolor; petals oboval or oblong-oboval ................................................................................... 8

8. Stem profusely branched with long branches; basal and apex leaves similar in size; leaflets 1–2.5 cm long, obcordate, spatulate or obtriangular, rarely oboval or elliptic; petiole 5–20 mm long; species from Suriname, Guiana, Venezuela and north and northeast of Brazil....................................................................................................................................................................... 15. Ch. major

- Stem fewer branched; basal leaves usually larger than the apex leaves; leaflets 3–4 cm long, elliptic, oboval, largely elliptic or suborbicular; petiole 22–42 mm long; species from Mexico, Bolivia, Colombia, Venezuela, Paraguay to the Midwest region of Brazil......................................................................................................................................................................... 18. Ch. viscosa

9. Branches, stipules, petiole, rachis and leaflets glabrous or densely villosule with tector trichomes, indumentum whitish; leaflets chartaceous with prominent and vinaceous midrib on the upper surface ....................................................................................... 10

- Branches, stipules, petiole, rachis and leaflets setulose-viscous with glandular and tector trichomes mixed, indumentum never whitish; leaflets papyraceous or membranous, discreet midrib on both sides and yellowish or greenish on the lower surface .... 11

10. Plant erect; branches and leaflets commonly villous, sometimes glabrous; ascending or patent leaves; erect inflorescences ........... ............................................................................................................................................................................ 13. Ch. juruenensis

- Creeping or decumbent plants; branches and leaflets commonly glabrous and less frequently villous; leaves opposite the ground; slightly curved inflorescences ....................................................................................................................... 17. Ch. roncadorensis

11. Creeping, procumbent or decumbent stems ................................................................................................................................... 12

- Erect stems ...................................................................................................................................................................................... 15

12. Petiole 1.5–2 times larger than the rachis; margin of leaflets revolute at least at apex or base; sessile inflorescence or falsely pedunculated due to first caduceus flower ..................................................................................................................................... 13

- Petiole 2.5–5 times larger than rachis; leaflet margin flat; inflorescence with peduncle 4–15 mm long ....................................... 14

13. Setulose-viscous and puberulent branches; concolor leaflets; orange or reddish petals .................................... 10. Ch. fagonioides

- Puberulent and non-viscous branches; slightly discolored leaflets; petals yellow ................................................. 8. Ch. carobinha

14. Leaflets rhomboid or oblique-oboval, never variegated; buds ovoid or globoid with obtuse apex ......................... 3. Ch. amiciella

- Leaflets oboval, oboval-elliptic, oblong-elliptic or suborbicular, variegated or not; buds ovoid or ellipsoid with an acute or apiculate apex ......................................................................................................................................................................... 11. Ch. hispidula

15. Leaflets 3–5.4 cm long, oval, largely elliptic or suborbicular; pedicel abruptly curved down when fruited; styles 2–2.2 cm long; legumes 6–6.5 cm long ...........................................................................................................................................14. Ch. longistyla

- Leaflets 0.6–3 cm long, elliptic, oblong, oval, obcordate or spatulate; pedicel straight and ascending when fruited; styles 0.8–1.3 cm long; legumes 2.5–5 cm long .................................................................................................................................................... 16

16. Leaflets concolor; pedicel 4–8 mm long; species from Paraguay and Midwest, North and Southeast regions of Brazil................... ................................................................................................................................................................................. 7. Ch. campestris

- Leaflets discolor; pedicel 8–18 mm long; species endemic of Chapada Diamantina (Bahia) in the Northeast region of Brazil....... ......................................................................................................................................................................................................... 17

17. Leaflets obcordate or spatulate with emarginate apex and revolute margin; racemes congest; buds with an obtuse and apiculate apex .......................................................................................................................................................................... 9. Ch. chapadae

- Leaflets elliptic, oblong-elliptic or oboval with obtuse or rounded apex and flat or revolute margin near the base or apex; racemes lax; buds with acuminate apex .............................................................................................................................. 12. Ch. jacobinea