Revisitando os embriões em Myrteae: uma perspectiva morfoanatômica, das reservas químicas e evolutiva

Abstract

The Myrteae tribe is the richest Neotropical tribe within the Myrtaceae family, with approximately 2,500 species and 51 genera. The high richness of the tribe is often considered a taxonomic nightmare among botanical families. To mitigate this effect, over the past two decades, there has been a movement to rescue different approaches in studies to not only assist in the taxonomy of the tribe but also to understand the evolutionary history and origin of diversification within Myrteae. Given the importance of embryo morphology for classical taxonomic and systematic studies in Myrtaceae, the main objective of this thesis was to study the relationship between protein, carbohydrate, and lipid reserves and the embryo morphotype among the genera of Myrteae. To this end, 27 species encompassing the richest Neotropical genera were subjected to morphoanatomical analysis, stereoscopic and scanning microscopy, light microscopy and histochemistry, chemical determination of soluble proteins, soluble sugars, starch, and total lipids. Additionally, each morphoanatomical and histochemical parameter found was transformed into character/state for the purpose of reconstructing the ancestral embryonic characters. Four groups of embryonic types were established for the genera (Eugenioid, Myrcioid, Pimentoid, and Plinioid), while Algrizea, Legrandia Kausel, Myrtastrum Burret, and Syzygium Gaertn. appeared as intermediate points. Thus, two reconstructions were performed in Mesquite with parsimony analysis of embryonic types by statistical character similarity and embryonic types sensu Berg with updates sensu Lucas. Complete morphoanatomical descriptions with illustrations, photographs, photomicrographs, and histochemistry for the sampled genera (Eugenia, Myrciaria, Plinia, Myrcia, Campomanesia, Pimenta, Psidium, Syzygium) are also presented. Finally, an extensive discussion is provided on the relationship between morphoanatomy, reserves, and the adaptive-evolutionary significance for Myrteae species, highlighting the suggestion that the ancestral Myrteae embryo was small, more like the myrtoid type, and that from this, embryo evolution seems to have followed three main morphological and reserve type pathways, with some specializations potentially arising in certain clades.