Origin and relationships of the austral genus Abrotanella (Asteraceae) inferred from DNA sequences

Relationships of the small austral genus Abrotanella are uncertain. It was previously included in the Anthemideae or more recently in the Senecioneae. We conducted a phylogenetic analysis of 39 accessions that included most species of Abrotanella and putative relatives including Blennosperma, Crocidium and Ischnea. These four genera have been considered to form subtribe Blennospermatinae. Our results suggest that the Blennospermatinae are polyphyletic; Blennosperme, Crocidium and Ischnea form a well-supported clade nested within the Senecioneae, while Abrotanella forms another well-supported clade that is distinct from these genera and its sister is not resolved. Molecular dating of Abrotanella suggests that the lineage initially diverged during the early Miocene. Secondary species radiations in Australasia and in southern South America that occurred 3 million years ago undoubtedly reflect long-distance dispersal, colonization and speciation. Both the ITS region and the 5' trnK/matK chloroplast DNA intron gave similar divergence estimates. The estimates were also robust to changes in the tree topology and to the different methods used to calculate divergence times.