Phylogenetic relationships and character evolution in <i>Primula</i> L.: The usefulness of ITS sequence data

The main goals of this research were to reconstruct the infrageneric phylogeny of the genus <i>Primula</i> based on both nuclear and chloroplast DNA sequences, and to use the resulting phylogenies to elucidate the evolution of breeding systems, morphological characters, chromosome number, and biogeographic distribution in the genus. In this paper, the results of a pilot study based on the nuclear ribosomal Internal Transcribed Spacer (ITS) region are described. ITS sequences from 21 taxa produced a number of variable characters sufficient to resolve relationships among sections. The resulting phylogeny confirmed the monophyly of sections <i>Auricula</i> and <i>Aleuritia</i>. Sections <i>Armerina</i>, <i>Proliferae</i>, <i>Crystallophlomis</i>, <i>Parryi</i>, and <i>Auricula</i>, with a base chromosome number of x = 11, and sect. <i>Aleuritia</i>, with a base chromosome number of x = 9, formed two well supported clades. The ITS topology also suggested that leaves with revolute vernation, previously believed to be a derived state, might represent the ancestral condition in <i>Primula</i>, with later reversals to the involute condition. Finally, this initial ITS tree provides preliminary support to the proposed role of the widespread, diploid and heterostylous <i>P. mistassinica</i> as having given origin to the polyploid, homostylous <i>P. incana</i> and <i>P. laurentiana</i>.