Sistemática de Oxalis L. sect. Thamnoxys (Endl.) Progel no Brasil

Abstract

The family Oxalidaceae R. Br comprises about 600 species in five genera. Noteworthy is the genus Oxalis L. as the most representative family with 500 species of tropical and subtropical distribution. This genus includes the most recent classification with four subgenera and 29 sections. Among the sections stands O. sect. Thamnoxys with 27 species of which eight are endemic to Brazil. Our objectives are to point out the relationships among the species of O. sect. Thamnoxys through the study of morphological phylogenetics, answering questions about the differentiation of species of this section occurring in Brazil and assess the character of the seed coat ornamentation in the delimitation of infrageneric and specific taxa. The study of phylogenetic relationships were based on 72 morphological characters and conducted by PAUP version 4.0b10, using the method of maximum parsimony. The analysis founded 53 equally parsimonious trees with 250 steps. The consensus tree showed CI = 0.32, RI = 0.4637 and RC = 0.1484. Oxalis sect. Thamnoxys proved to be paraphyletic by the inclusion of O. densifolia (O. sect. Foliosae) and subclade formed by O. cordata and O. hirsutissima (O. sect. Robustão), O. rhombovata (sect. Polymorphae), O. mandioccana (O. sect. Holophyllum), O. psoraleoides (O. sect. Psoraleoideae) and O. fruticosa (O. sect. Phyllodoxys) in its constituency and the subgenus Thamnoxys presented monophyletic. The species of the section Thamnoxys formed some subclades Foliosae section and was more closely related to section Thamnoxys. The taxonomic studies were based on approximately 2000 derived from herbarium specimens and herbarium collections themselves. In Brazil there are 18 species of Oxalis sect. Thamnoxys, differentiated mainly by vegetative characters related to the presence of xylopodium, shape, number and distribution of leaflets and indumentum reproductive character and coloration of the corolla. It was proposed to sinonimization four varieties and one form. The study of the microstructure of the seed coat was performed by scanning electron microscopy (MEV). The seed coat sculpture presented in five different categories: foveolar, sidetransverse, longitudinal-side, split-back and split longitudinally, which in part reflect the infrageneric classification of Oxalis.