Revealing leaf structure characters of taxa of Campomanesia Ruiz & Pav. (Myrtaceae) to use in the taxonomy of the genus

Leaf structure studies focused on anatomy have helped resolve taxonomic problems in Myrtaceae, demonstrating they are a promising method to better understand poorly known groups. Taxonomically delimiting sterile specimens of Campomanesia is difficult, although this group has leaf structure characters that are little explored in the literature. The present study had the objectives of describing the leaf structure characters of Campomanesia and determining their potential to delaminate taxa. The leaf architecture varied among the species: secondary veins are excurrent or decurrent, with alternate to irregular arrangements; and tertiary veins are percurrent alternate, mixed, or opposite. Freely ending veinlets range from unbranched to highly branched (dendritic), offering potential characters to separate species based on venation complexity. The leaves are dorsiventral and hypostomatic, with a median vascular bundle forming a continuous arch with ends that turn upward or toward the center. This pattern suggests structural adaptations that may be conserved within clades and, thus, might be useful for taxonomic grouping. Petioles have vascular arches that are either invaginated or directed towards the center, and these variations, along with the continuity or discontinuity of the arch, provide additional anatomical markers for species delimitation. The lateral veins have sheath extensions, and aligned secretory cavities can occur in both epidermis surfaces or only in the abaxial surface. The distribution of secretory cavities has proven to be a useful trait for species differentiation in Myrtaceae, which is corroborated here for Campomanesia. These findings demonstrate that leaf structural features are consistent and diverse enough to serve as reliable characters for species delimitation within Campomanesia.