The 20 North American species comprising subtribe Maurandyinae have been treated in four to seven genera and are noteworthy for exhibiting a diversity of floral morphologies and wide interspecific compatibilities in artificial crosses. To test taxonomic hypotheses and to evaluate inferences about genetic relatedness based on crossing and interfertility data, 15 ingroup and four outgroup species were analyzed for nucleotide variation among nrDNA ITS sequences. Parsimony analyses result in a high level of support for monophyly of the group and sister group status for the SW European and Mediterranean genera Asarina and Cymbalaria. Within the Maurandyinae, two main clades with moderate levels of support are delineated: Maurandya + Epixiphium + Holmgrenanthe and Mabrya + Lophospermum. Biogeographic analyses suggest a basal diversification in arid habitats with a subsequent radiation into more mesic habitats in southern Mexico and Guatemala. The frequently segregated monotypic genera Epixiphium and Holmgrenanthe are characterized by long branch lengths and the lowest indices of crossability in the group. Species previously segregated in Mabrya appear paraphyletic, supporting their merger in an expanded Lophospermum and consistent with their moderate levels of ‘intergeneric’ hybrid fertilities. The highest indices of crossability and interfertility are found in species of Maurandya and Lophospermum that have the closest topological placement on ITS trees.

Key words: crossing data, generic delimitation, ITS, Maurandyinae, Veronicaceae