Phylogenetic reconstruction of the South American genus Leucheria Lag. (Asteraceae, Nassauvieae) based on nuclear and chloroplast DNA sequences

The genus Leucheria Lag. (Asteraceae Bercht. and J. Presl, tribe Nassauvieae Cass.) comprises 45 species and three infraspecific taxa distributed in the Andean region from southern Chile and Argentina to Peru. Six species are annual herbs. The genus has had a long taxonomic history involving the transference of species described originally under many different genera. The main objectives of this paper were to determine the phylogenetic relationships of species of Leucheria, examine the hypothesis that the ancestor of Leucheria would have originated in a forested habitat and examine the validity of nine morphologically defined evolutionary lines recognized in earlier work on the genus. Additionally we investigated whether the annual species of Leucheria are derived. We extracted DNA from leaf material for 45 taxa (94%) of Leucheria. We used Bayesian inference and plastid and nuclear genes to construct a phylogenetic hypothesis. Results show that Leucheria is monophyletic and is comprised of two main clades. One clade comprises perennial acaulescent/subacaulescent species, all with a solitary capitulum. We recognized three lineages in the second clade comprised of caulescent species that exhibit multiple capitula. Optimization of life-form over the phylogeny showed that five of the six annual species studied are derived in our tree. We conclude that the appearance of the annual habit is associated with the colonization of arid conditions in the winter rainfall coastal desert of northern Chile. Our result shows that species of Leucheria from forested habitats are derived. Discrepancies with previously recognized morphologically defined evolutionary lines were detected.