ANATOMIA E CITOGENÉTICA APLICADAS À TAXONOMIA DO COMPLEXO DE ESPÉCIES Commelina erecta (COMMELINACEAE)

Abstract

The cryptic species Commelina erecta exhibits phenotypic plasticity according to the environment, generating a dilemma about whether its different morphotypes should be considered new species or not. In this study, we adopted an integrative systematic approach, combining morphology, anatomy, and cytogenetics, to enhance the taxonomy of the group and facilitate its classification. We collected morphotypes of the Commelina erecta complex from distinct locations, including Acre, Santa Catarina, Mato Grosso do Sul, and the Entre Rios region in Uruguay, along with the closely related species C. catharinensis, C. dielsii, and the C. cf. dielsii morphotype, to elucidate the taxonomic relationship among them through anatomy and cytogenetics. In the study of plant anatomy, we used leaves from each morphotype fixed in historesin to evaluate anatomical structures in cross-sections (mesophyll, epidermis, and margins), and the Franklin method to assess the epidermal surface and its margins. We made the first record of paracytic, tetracytic, pentacytic, and heptacytic stomata in the genus Commelina, as well as the first record of wide-based multicellular trichomes in the group. The separation of C. catharinensis and C. dielsii as distinct species, the last one exhibiting pentacytic and heptacytic stomata diagnostic of the species, was confirmed. In terms of cytogenetics, we conducted detailed studies using apical meristems from roots on slides to determine the karyotype of each morphotype regarding the number and chromosomal morphology during mitosis (2n) of all collected morphotypes. Commelina erecta exhibited 2n = 60 in the morphotypes from Santa Catarina, Acre, and Uruguay, with chromosomal formulas of 30m + 26sm + 4st (Acre), 26m + 30sm + 4st (Santa Catarina), and 24m + 32sm + 4st (Uruguay), and 2n = 42 in the Mato Grosso do Sul morphotype, with a chromosomal formula of 20m + 18sm + 4st. Commelina catharinensis had 2n = 46, with a formula of 22m + 18sm + 6st. Commelina dielsii exhibited a karyotype of 2n = 38, with a chromosomal formula of 18m + 16sm + 4st, and the C. cf. dielsii morphotype had 2n = 38, with a formula of 22m + 12sm + 4st. We confirmed that C. catharinensis and C. dielsii are distinct species from C. erecta, as they have characteristic karyotypes. Additionally, the C. cf. dielsii morphotype is likely to be C. dielsii, considering its chromosomal number, chromosomal formula, and morphological characteristics. These results can help elucidate the taxonomy of the group and contribute to the advancement of systematic knowledge about the genus Commelina.