Evolution and taxonomic meaning of seed fatty acid profiles of Campomanesia (Myrtaceae)

Abstract The present work aimed to determine the fatty acid (FA) composition of seed oils of Campomanesia (Myrtaceae), a genus with approximately 45 species restricted to South America. The work aimed also to evaluate the systematic bearing of FA profiles, as well as their degree of congruence with phylogeny. Seeds of Psidium guajava and seven species of Campomanesia were collected from at least two individuals from distinct populations. The seed oils were extracted and the methyl esters of the FA were analyzed by gas chromatography and mass spectrometry. Nucleotide sequences from GenBank of the same species, regarding the internal transcribed spacer of ribosomal DNA (ITS), were used for phylogenetic analysis. Seed FA profiles were distinct, comparing Campomanesia and Psidium guajava ; linoleic acid predominates in the seed oil of the latter species, while saturated and mono-unsaturated FA predominate in the seed oil of Campomanesia . A high similarity of FA profiles was noted, when comparing specimens of the same species. With few exceptions, cluster and principal component analyses based on FA profiles were congruent with phylogeny based on ITS sequences. Distribution of seed FA supports the non-monophyletic status of the “ C. xanthocarpa complex”. Reconstruction of ancestral character states revealed distinct evolutionary trajectories of FA profiles toward differentiation of Campomanesia clades, all of them leading to decreased proportions of unsaturated FA.