LEAF MORPHOANATOMIC TRAITS AND INFLUENCE ON HERBIVORY AND COEXISTENCE OF TWO MICROGRAMMA SPECIES (POLYPODIACEAE) IN AN AMAZON FOREST FRAGMENT

Epiphytes, histochemistry, ecological interactions, glandular trichomes

About 29% of fern species (i.e. seedless vascular plants) are epiphytes, representing a diverse and important group in the canopy of tropical forests. Epiphytic ferns typically show water stress tolerance characteristics, resisting desiccation. However, this set of tolerance characteristics does not include morphoanatomical information, which is useful for ecological interpretations. Therefore, this study aimed to determine and compare morphoanatomical characteristics of Microgramma lycopodioides (L.) Copel. and M. reptans (Cav.) A.R.Sm., performing ecological interpretations of the convergence or divergence of characteristics in relation to the epiphytic habitat, as well as their effects on herbivory. The study took place in the Utinga State Park, an urban forest fragment, located within the Belém Endemism Center. The species were sampled in phorophytes close to the forest edge. About 60 leaves were collected for anatomical analyses, according to the usual fixation protocols, light, and scan electronic microscopy, and histochemical analyses. Additionally, 90 leaves were collected to measure herbivory damage, classifying the leaves into the following established categories: intact leaves, 0.01-1%, 1-5%, 5-25%, 25-50%, 50-75% and 75-100% of leaf area removed. The histochemical tests performed on the secretory structures of the studied species were positive for phenolic compounds, total lipids, acidic mucilages and alkaloids. These results demonstrated that several structural and histochemical characteristics, present in Microgramma, are related to the adaptation of these epiphytes in extreme environments with high luminosity and water deficit, such as forest edges, thus avoiding water loss. Despite being species belonging to the same genus, it was noted that individuals of M. reptans may have adapted to the environment and herbivores, developing different characteristics. However, it is necessary to investigate the knowledge of morphofunctional attributes, especially about the diagnosis of secretory structures and their co-evolution in different groups of ferns.