Foliar anatomy and comparative micromorphology applied to the taxonomy of Agarista D. Don ex G. Don (Ericaceae): patterns and implications

In Brazil, Agarista is the second most diverse genus of the family Ericaceae, comprising 22 species, 20 of which are endemic. In this study, we analyzed mature leaves from the third node of 26 specimens representing ten Agarista species using light microscopy and scanning electron microscopy (SEM). Nine of the analyzed species are endemic to Brazil (except Agarista eucalyptoides), and nearly all have their leaf anatomy described here for the first time (except A. oleifolia). We emphasized leaf morphology and architecture, as well as epidermal and anatomical patterns in transverse sections, to understand the implications of these data for taxonomic proposals within the genus. Most epidermal patterns and leaf architecture were similar among the analyzed species. However, the presence, absence, and types of trichomes proved to be important diagnostic characters. In transverse sections, additional taxonomically relevant features were observed, such as a hypodermis associated with secondary veins, variation in the collenchyma of the leaf margins, and in the structure of the central and secondary vascular bundles. Expanding this study to include additional Agarista species will significantly enhance the taxonomic and anatomical understanding of South American genera.