The genus Senna Mill . ( Leguminosae : Caesalpinioideae ) in the Serra Geral of Licínio de Almeida , Bahia , Brazil

Senna includes about 300 species with circumtropical distribution, widely represented in the Americas, also occurring in Africa, Australia, Asia and Oceania. The genus is represented in Brazil by 80 species, of which 26 are endemic. The Serra Geral de Licínio de Almeida (SGLA), situated in the central portion of the Cadeia do Espinhaço, state of Bahia, Brazil, presents areas relatively little studied, with great potential for the registration of new information about Brazilian biodiversity. The floristic survey of Senna in the SGLA included analysis of specimens collected from February 2012 to October 2013. The analyses were supplemented with dried collections from the following herbaria: ALCB, BHCB, HUEFS, HUNEB, HRB, MBM and SPF.The genus is represented in the study area by 14 taxa, the most representative in the area were: S. silvestris subsp. bifaria var. bifaria, S. macranthera var. striata and S. macranthera var. nervosa, occurring principally in cerrado environments. The taxonomic treatment includes a key for the identification, descriptions, illustrations, photos, data of the geographical distribution, reproductive phenology and comments about the taxa.

Senna includes about 300 species, is circumtropical and is most represented in the Americas, but also occurs in Africa, Australia, Asia and Oceania (Lewis, Schrire, Mackinder, & Lock, 2005).There are 80 species in Brazil, of which 26 are endemic (Souza & Bortoluzzi, 2015).
Among the most important characters for distinguishing the genus is the presence of a zygomorphic androecium with three abaxial stamens; presence of convex, claviform to pyramidal extrafloral nectaries and cylindrical or plane-compressed fruit with inert dehiscence.
The most comprehensive study of the group was the revision done by Irwin and Barneby (1982), which recognized 260 species.In Brazil, work has dealt with reports of new occurrences, such as Bortoluzzi, Miotto and Reis (2007) for the flora of southern Brazil, and the descriptions of new species such as Araújo and Souza (2007) for Tocantins and Irwin and Barneby (1985) and Cardoso and Queiroz (2008) for Bahia.Among regional work with the genus Senna in Brazil are Lewis (1987) for Bahia; Lewis (1995) for Pico das Almas (Bahia); Rodrigues, Flores, Miotto and Baptista (2005) for Rio Grande do Sul; Dantas and Silva (2013) for Parque Estadual da Serra Dourada (Goiás), and Rando, Hervencio, Souza, Giulietti and Pirani (2013) for Serra do Cipó (Minas Gerais).Studies of floristic surveys for the genus in Brazil showed that the number of works remains few, especially those with descriptions and identification keys.
Given the significant representation of the genus Senna in the flora of the state of Bahia, and especially in the Cerrado, this study aimed to better comprehend the diversity of this group in the Serra Geral de Licínio de Almeida (SGLA), Bahia, Brazil, to contribute to the knowledge of the flora of the state, as well as provided support for the development of a plan for a future conservation unit.

Study area
The Serra Geral de Licínio de Almeida -SGLA (Figure 1) is located in the central portion of the Espinhaço Range (Cadeia do Espinhaço), a mountain range that extends from the Serra de Ouro Preto in Minas Gerais to Bahia, forming a divide between the basin of São Francisco River and the Atlantic Ocean (Giulietti, Menezes, Pirani, Meguro, & Wanderley, 1987).It occupies a band of mountains located west of the municipality of Licínio de Almeida in southeastern Bahia between the latitudes of 14º26' to 14º50' S and longitudes of 42º36' to 42º29' W. It encompasses an area of approximately 24,000 ha, with altitudes varying from 700 to 1230 m, and borders the municipalities of Caetité, Jacaraci, Pindaí and Urandi.The vegetation of the region is predominantly cerrado, campo rupestre and gallery forest in localities at altitudes between 900-1230 m, but there is also caatinga vegetation present.The climate is semiarid and subhumid, with average annual rainfall of 500 to 1000 mm and average annual temperature of 21ºC.The soils are, in general, formed by latosol and quartzarenic neosol [quartzite sand] (Bahia, 2007).

Taxonomic study
The study was based on fieldwork carried from February 2012 to October 2013, besides information complemented by the analysis of specimens deposited in the following herbaria: ALCB, HUEFS, HUNEB, HRB, MBM and SPF (acronyms according to Thiers, 2017 continuously updated).The field collections and observations were performed during random walks exploring most of the study area.The herborization and material processing followed the methodology by Fosberg and Sachet (1965) and Mori, Mattos-Silva, Lisboa and Coradin (1989), where fertile material was collected with flowers and/or fruit.The specimens were deposited in the herbarium of the Universidade Estadual da Bahia (HUNEB -Collection Paulo Afonso) and the duplicates will be sent to the main herbaria in the state of Bahia (ALCB, HRB and HUEFS).
The identifications were made based mainly on specialized bibliographies (e.g., Irwin and Barneby (1982), Lewis (1987), protologues, photos of type collections and consulting of the collections in the herbaria that were visited.For the taxonomic desc riptions, the terminologies proposed by Radford, Dickison and Massey (1974), Irwin and Barneby (1982) and Harris and Harris (1994) were adopted.Phenological data refers to the observations made in the study area.The taxonomic treatment includes a key for the identification, descriptions, illustrations, photos, data of the geographical distribution, economic potential and reproductive phenology and comments about the taxa.
Senna acuruensis is endemic to Brazil and widespread in Bahia, but is also distributed in the states of Alagoas, Minas Gerais, and Pernambuco (Souza & Bortoluzzi, 2015).The species encompasses three varieties (Irwin & Barneby, 1982), and in the SGLA is represented by Senna acuruensis var.acuruensis, which is restricted to Bahia, Alagoas and Pernambuco (Irwin & Barneby, 1982), and found associated with areas of cerrado and caatinga on argillaceous and very rocky soils.It flowers from February to April.
The variety is endemic to Brazil, with records for Bahia, Distrito Federal, Goiás, Mato Grosso, Minas Gerais, Rio de Janeiro and São Paulo, and is common in cerrado, riparian or gallery forest and degraded areas (Souza & Bortoluzzi, 2015).In SGLA it occurs in areas of cerrado where it was found flowering in February.
The taxon can be confused with S. macranthera var.micans (see comments in S. var.micans).
Senna obtusifolia is widely distributed in the Americas, occurring from Argentina to the United States, and has been introduced to Africa and Asia (Irwin & Barneby, 1982).In Brazil, it is recorded in the majority of states and in all regions, and is common on the shores of lakes and rivers, becoming a weed in pastures and crops, along roads, in desolate places and on farms and at homes (Irwin & Barneby, 1982;Souza & Bortoluzzi, 2015).In the study area it was collected in anthropized environments on sandy or rocky soils, and with flower in February.
Senna occidentalis encompasses tropical and subtropical America, Asia, Africa, and Australia, and is widely distributed throughout Brazil being recorded in each state (Irwin & Barneby, 1982;Souza & Bortoluzzi, 2015).A ruderal species that occurs in disturbed environments such as roads, pastures and open areas (Irwin & Barneby, 1982).In the study area, it occurs in disturbed areas on sandy and rocky soils.It was collected in flower in February and April and fruiting in February.
The species is easily recognized by the presence of an extrafloral nectary on the pulvinus, a characteristic not encountered among congener species in the area, and by the presence of oval-elliptical proximal leaflets and elliptical distant leaflets.
The species in known from Mexico to Argentina.In Brazil, it occurs in the majority of the states, with the exception of some states in the North and Northeast regions, in addition to Rio de Janeiro (Irwin & Barneby, 1982;Souza & Bortoluzzi, 2015).Irwin and Barneby (1982) recognized 19 varieties for S. pendula, of which only two occur in Bahia: S. pendula var.glabrata and S. pendula var.dolichandra.In the study area, only S. pendula var.glabrata was recorded, which is distributed form the north to the south of Brazil, occurring in Bahia, Goiás, Distrito Federal, Mato Grosso, Mato Grosso do Sul, Minas Gerais, Pará, Rio de Janeiro and São Paulo (Irwin & Barneby, 1982;Souza & Bortoluzzi, 2015).Generally it is found in cerrado, campo rupestre, areas of contact with caatinga and seasonal forest, and can be ruderal (Souza & Bortoluzzi, 2015).In SGLA it was collected in an anthropized environment on argillaceous and rocky soils and flowers in April.
The species is endemic to Brazil with occurrences in the states of Bahia, Minas Gerais, Sergipe and São Paulo, where it is common in caatinga and the cerrado (Irwin & Barneby, 1982;Souza & Bortoluzzi, 2015).In SGLA it occurs in riparian forest environments and was collected in flower in April and May and fruiting in June.
The species is endemic to the Northeast Region of Brazil, and occurs in all of the states where it is common in caatinga and cerrado (Souza & Bortoluzzi, 2015).In the study area, it was collected in an anthropized area with flowers in October.
Senna rizzinii can be recognized in the study area by having two pairs of elliptical and ovate leaflets, apex rounded and obtuse, extrafloral nectary located between the proximal pair of leaflets and suborbicular persistent bracts.Of the species recorded for SGLA, it most resembles S. macranthera, however it can easily be distinguished by having suborbicular persistent bracts and flowers of 3-5 cm in diameter (vs.lanceolate-ovate deciduous bracts and flowers of 3.5-6 cm diameter in S. macranthera).
The species can be recognized by the presence of lutescent trichomes covering mainly the branches, petiole, leaflets, sepals and petals; petioles relatively short, shorter than the rachis; leaflets leathery, rugose with extrafloral nectaries located between the pairs of leaflets.In the study area it can be confused with S. macranthera, but differs in having a shorter petiole, 2.5-10 (-15) mm, that is usually shorter than the rachis, leathery leaflets with extrafloral nectaries located between the two pairs of leaflets (vs.petiole 9-37 mm, usually longer than rachis, leaflets papyraceous with extrafloral nectaries located between the proximal pair of leaflets in S. macranthera).
The taxon can be recognized in SGLA by the absence of extrafloral nectaries, leaves with 6-7 pairs of leaflets and yellow petals with a yellow-orange base.It can be confused with S. spectabilis var.excelsa in the study area, but the two taxa can be distinguished by S. silvestris var.bifaria having paniculate-corymbose inflorescences, yellow petals with a yellow-orange base and heteromorphic stamens (vs.paniculate or racemose inflorescences, flowers with yellow petals and almost isomorphic stamens in S. silvestris var.excelsa).
Senna splendida occurs in Paraguay, Brazil, Uruguay, Africa and the Malayan Peninsula (Irwin & Barneby, 1982).In Brazil it occurs in all the states of the Northeast and Southeast regions, and in the states of Mato Grosso do Sul and Paraná (Souza & Bortoluzzi, 2015).According to Irwin and Barneby (1982) the species has two varieties, of which S. splendida var.gloriosa was catalogued for the study area.The taxon is endemic to Brazil, occurring in the states of Alagoas, Bahia, Ceará, Minas Gerais, Paraíba, Pernambuco and Rio Grande do Norte, in areas of caatinga, cerrado, ombrophilous forest and restinga (Irwin & Barneby, 1982, Souza & Bortoluzzi, 2015).In SGLA, S. splendida var.gloriosa occurs in edges of forest and cerrado on argillaceous and rocky soils.It was collected with flowers in March and October and fruits in April and November.
In SGLA, the taxon can be recognized by having oblanceolated stipules with acute apices; leaves with two pairs of lanceolate-elliptical, papyraceous, glabrous leaflets; oblong-lanceolated external sepals and the presence of a strigulose indumentum on the gynoecium and fruits.In the study area, it can be confused with S. macranthera because both possess leaves with two pairs of leaflets, extrafloral nectaries between the proximal pair of leaflets, relatively large flowers and heteromorphic anthers.Senna splendida var.gloriosa differs from Senna macranthera by having oblanceolate stipules, glabrous leaves and oblonglanceolated external sepals (vs.linear-lanceolate, leaflets puberulous or pubescent and oval external sepals S. macranthera).

Conclusion
A total of 14 taxa of the genus Senna were recorded in SGLA.The most representative species in the area were S. silvestris subsp.bifaria var.bifaria, S. macranthera var.striata and S. macranthera var.nervosa, occurring principally in cerrado environments.The occurrence of Senna reniformis was restricted, and associated with the riparian forest environment.Two taxa had wide distributions in SGLA, S. cana var.cana and S. rugosa, occurring in cerrado, campo rupestre, caatinga, riparian forest and anthropized environments.