O “Complexo Polyphylla” em Senegalia Raf. (Leguminosae Juss.: “Clado Mimosoideae”): abordagens morfoanatômica e taxonômica

Abstract

Leguminosae is the third largest family of angiosperms, including approximately 19,580 species with cosmopolitan distribution. The traditional arrangement of this family divided into three subfamilies does not reflect the current knowledge of phylogenetic relationships and a new classification was proposed in 2017. Currently in Caesalpinioideae is the "Mimosoideae Clade", which includes Senegalia Raf. with about 217 species distributed in the tropical and subtropical regions of the world. This genus presents some species of difficult taxonomic delimitation due to the overlap of morphological characters between the individuals, creating the "species complexes". One of these complexes is the "Polyphylla Complex", which is composed of the species S. giganticarpa, S. polyphylla, S. rhytidocarpa, S. loretensis, S. kallunkiae and S. klugii. This work aims to investigate morphological and anatomical parameters that may be useful in the differentiating of this complex. All species cited before were analyzed, with exception of S. klugii. To achieve the proposed aims were accomplished: (1) morphometric analyzes of vegetative and reproductive characteristics; (2) investigation of the foliar anatomy, including the petiole, rachis and leaflets; and (3) the anatomy and histochemistry of extrafloral nectaries on the petiole and rachis. Through the morphometric analysis, we observed that the leaf-related characters were extremely useful both in the segregation and hierarchization of the studied specimens, allowing a clear individualization of the species of the complex. The anatomical analyzes were also useful in the segregation of the species, mainly the conformation of the vascular bundles; presence of trichomes; conformation of the distal rachis; leaflet morphology; number of smaller caliber veins; projection of the largest caliber vein of leaflets. The extrafloral nectaries mainly in relation to the position, number and morphology of it in the petiole and rachis are used in the taxonomic delimitation of Senegalia species; however, the morphanatomic similarity found among the members of the "Polyphylla Complex" does not allow a clear identification. In addition, histochemical tests identified the same groups of chemical compounds for the species studied. Therefore, although the anatomical analyzes carried out do not clearly segregate taxonomically the species, the similarities found confirm that the species of the “Polyphylla Complex” are closely related. We conclude that the species S. giganticarpa, S. polyphylla, S. rhytidocarpa and S. loretensis are closely related. Senegalia kallunkiae presents unique morphoanatomic patterns in relation to the other species of the "Polyphylla Complex” and should not be considered part of this Complex of species.