Anatomia foliar e sua importância nas relações filogenéticas do Clado Chapada Diamantina (Eupatorieae, Asteraceae)

Abstract

Recent molecular studies have recovered the Chapada Diamantina clade (Eupatorieae-Asteraceae), endemic to the Espinhaço Range, Brazil, comprising 30 species distributed in six clusters. However, some clusters obtained low support and five species were segregated from their genera. Among the tools for solving taxonomic problems, the anatomical characters of vegetative organs have shown to be important morphological markers of evolutionary processes. Thus, this study aims to describe the leaf anatomy of representatives of six clusters of the Chapada Diamantina clade. Different populations of 16 species distributed in six genera belonging to the clade were analyzed, besides two species representing the external group. The collected materials were deposited in the Herbário ALCB and also fixed in 70% FAA, to obtain the paradhermal sections from the dissociation by Franklin's method and transversal sections from material included in Historesin and later sectioned in rotary microtome. Staining was done according to the usual techniques for both forms of obtaining the sections, which were later analyzed and photomicrographed under light and scanning electron microscopy at LAVIM-UFBA and IGM-FIOCRUZ, respectively. Among the main results: a) The position of the secretory channels in the main vein associated with the vascular bundles is a probable synapomorphy for the clade (vs. secretory channels dispersed in the fundamental parenchyma); b) Hypoestomatic leaf blades and the presence of stomata in stomatal crypts supported the genera Lasiolaena and Stylotrichium as sister groups; c) Epidermal cell contour and amphistomatic blades corroborated the inclusion of Arrojadocharis praxeloides and Lasiolaena pereirae in the genus Agrianthus; d) Type XI tector trichomes are exclusive to Bishopiella elegans; e) Type VII tector trichomes are exclusive to Lasiolaena; f) Isobilateral mesophyll and accessory bundles in the vein are exclusive to Eupatoriae sp. nov.; g) The species presented macro and micromorphological characters that have adaptive values to the rupestrian field vegetation, such as coriaceous, imbricate leaves, reduced leaf area, thick cuticle, high density of trichomes, stomata in crypts, hypodermis and extension of sheath in the mesophyll. From the analysis of the leaf anatomy of the species of the Chapada Diamantina clade, we concluded that the leaf anatomical characters corroborated most of the groupings proposed in the molecular phylogeny, besides reflecting important adaptations to the campos rupestres, vegetation in which all species are endemic.