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Phylogeny of Eugenia and Eugeniinae (Myrtaceae)

Collecting Eugenia convexinervia in Brazil. © Eve Lucas

Myrtaceae is one of the most important families in Brazil, often being one of the dominant woody families in the Mata Atlântica. Eugenia is the largest genus in neotropical Myrtaceae comprising >500 species and occurring from Mexico and the Caribbean to Northern Argentina.  Eugenia is well represented in Brazil by about 350 species, occurring mainly in forests but also found in campos rupestre, caatinga and cerrado vegetation. Eugenia belongs to subtribe Eugeniinae (sensu Berg- see 'Phylogeny of subtribe Myrciinae' project for an explanation of subtribes), a subtribe within which generic limits are vague and more taxonomic studies are urgently needed as the habitats in which the genus is particularly diverse are severely threatened by human activity. 

Eugeniinae is defined by having a homogenous embryo with cotyledons swollen and often fused and an extremely reduced hypocotyl.  Genera included in this study are Calycorectes, Eugenia, Hexachlamys, Myrcianthes, Myrciaria, Neomitranthes, Plinia and, Siphoneugena. 

In the nineteenth century, Otto Berg recognised eight sections in Eugenia, based on inflorescence type, sections Uniflorae, Biflorae, Glomeratae, Umbellatae, Corymbiflorae, Racemulosae, Dichotomae and Racemosae. This project forms part of doctoral studies underway in collaboration with the University of São Paulo, Escola Superior de Agricultura Luiz de Queiroz (Brazil) on Eugenia sect. Racemosae and Racemulosae, in particular those species occurring in Brazil.  The objectives of this study are (1) to produce a robust phylogeny of subtribe Eugeniinae in order to clarify generic boundaries, (2) to test the monophyly of Eugenia and establish its position relative to the other genera of the Eugeniinae, (3) to test the monophyly of the sections of Eugenia as recognised by Otto Berg. 

Approximately 60 Eugeniinae samples have been added to the Kew DNA bank, each species has been sequenced for the DNA regions ITS, ETS and psbA-trnH.  Results indicate Eugenia to be monophyletic and that there is some cohesion amongst the species of Otto Berg’s sections, in particular that section Racemosae is monophyletic, supported by the morphological character of inflorescences exclusively in racemes.  This represents the first steps in bringing an unwieldy and large genus under control and to a point where monophyletic sections can be monographed sequentially.  Results are in preparation for publication. 

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