Eucalyptus subgenus Symphyomyrtus: sections: Exsertaria, Latoangulatae and Maidenaria.

Abstract: Eucalypts are the most planted hardwood in the world, with 30 million ha. under cultivation. There are approximately 700 species of eucalypts, but more than 90 % of the plantations are concentrated in nine species of the Subgenus Symphyomyrtus in the Sections Exsertaria, Latoangulatae and Maidenaria. Since 2000, with the advancement of biotechnology, many species have been reclassified and regrouped according to their morphological and physiological characteristics, DNA structure and geographic distribution. This work had as its objective the formulation of a critical analysis which presents the main characteristics that will identify the species of Eucalyptus of these new sections. The species are classified mainly according to geographic distribution, where crosses occur; as evolution in the subgenus Symphyomyrtus is preferably reticulated (with backcrosses), which makes it difficult to identify the rate by molecular and morphological markers. Environmental ecological similarity will define whether the hybrid will become a new species or regress to one parent and become an ecotype. The hybrid will become a new species when it has ecological characteristics different from its parents