Phylogeny of Veronica--a combination of molecular and chemical evidence.

A molecular phylogenetic tree of the genus Veronica, based on sequences of the ITS region of nuclear ribosomal DNA, provided a framework to test the use of iridoid chemical data in the classification of the genus. The distribution of ten iridoid glucosides, determined in 27 species of Veronica, supported the molecular results. The nine clades of the molecular tree appeared to correlate with a specific pattern of catalpol esters and chromosome base numbers. Some relationships within Veronica, previously suggested on the basis of morphological and karyological characters, were supported by our data. Neither the molecular, nor the chemical features were in favour of the classical circumscription and classification of the genus.