A molecular phylogenetic study of subtribe Coreopsidinae was conducted using ITS sequences from 18 genera traditionally placed in the subtribe. The two largest genera Bidens and Coreopsis do not appear monophyletic, and occur instead in several strongly supported lineages. The small genus Coreocarpus is resolved into three distinct lineages. Although based on somewhat limited taxon sampling, both Cosmos and Dahlia occur as monophyletic groups, with Dahlia a basal lineage within the subtribe. The ITS phylogeny does not support the inclusion of the two island genera Petrobium and Oparanthus in Bidens, as has been suggested. Strong support is provided for inclusion of the insular genus Fitchia in Coreopsidinae, with Oparanthus appearing sister to it. Prior investigations of the subtribe have included grouping genera to reflect relationships and cladistic analyses of morphological characters; certain results of the present study are concordant with previous studies whereas in other instances sharply different relationships are portrayed. The molecular phylogeny resolves a number of strongly supported lineages within Coreopsidinae, but there is not always clear resolution of relationships among the lineages.

Key words: Coreopsidinae, ITS sequences, molecular phylogeny