Phylogenie und Systematik der Brassicaceae
Final Report Abstract
The evolutionary history of the Brassicaceae appeared as an enigma. The present study deepens our understanding of a familywide phylogeny by using new approaches in phylogenetic family-wide research. Using a slow-evolving mitochondrial marker (nad4 intron 1), we reconstructed the largest phylogeny in generic representation for the family to date. In addition, we adopted a supermatrix approach by concatenating all sequences available on GenBank as well as new sequences for a total 207 curently recognized genera and seven markers representing a comprehensive coverage of all three genomes. The supermatarix was then dated under an uncorrelated relaxed molecular clock using a direct fossil calibration approach. Finally, a lineage-throughtime-plot (LTT) and rates of diversification for the family were generated. The resulting tree, the largest in number of genera and markers sampled to date, provides important insights into the systematics of the family on a broad scale. However, the backbone of tree remained unresolved and is interpreted as the consequence of an early rapid radiation within the family. The age of the family was inferred to be 37.6 (24.2?49.4) myr, which largely agrees with previous studies. Analysis of diversification suggests that Brassicaceae underwent a rapid period of diversification, after the split with the early diverging tribe Aethionemeae. Given the dates found here, the family appears to have originated in or near the eastern Mediterranean region from a common ancestor of its sister family Cleomaceae under a warm and humid climate ca. 37 myr ago. We suggest that the rapid radiation detected was caused by a global cooling during the Oligocene coupled with a genome duplication event. This duplication could have allowed the family to rapidly adapt to the changing climate. More data shall be necessary in order to fully confirm the hypotheses advanced here.
Publications
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2006. Evolution and phylogeny of Brassicaceae. Plant Systematics and Evolution Spec.Vol. 259: 82-258
Koch, M, Mummenhoff, K.
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2009. Arabidopsis family ties: Molecular phylogeny and age estimates in the Brassicaceae. Taxon 58: 425-437
Franzke, A., German, D., Al-Shehbaz, I. A., Mummenhoff, K.
