XVI International Botanical Congess

Plantago media is a widespread herbaceous autopolyploid complex from Eurasian alkaline grasslands, comprising of diploid and tetraploid cytotypes with mutually exclusive distributions. Chloroplast RFLP's were studied to reconstruct the phylogenetic relationships between cytotypes within the species and between populations within cytotypes. The results indicate at least three independent origins of tetraploids. The phylogeography within cytotypes shows clear signs of major post-Pleistocene migrations. Furthermore, the phylogeography supports a non-adaptive explanation for the different cytotype distributions. The contact zone between a 2x and a 4x area in the Pyrenees is shown to be secondary, suggesting that flowering time differentiation in sympatric cytotype populations is the consequence of reproductive character displacement driven by 3x hybrid inviability.