Phylography and polyploid evolution in Cyanus Mill. (Centaurea L. section Cyanus Mill.)

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Gene flow among closely related species is often associated with speciation or singular events but rarely appreciated as a factor shaping the genetic structure of species in a repeated or regular manner. Our aim is to investigate the geographic patterns of genetic variation in the taxonomically difficult genus Cyanus (Asteraceae, Centaureinae) with chloroplast and nuclear DMA markers. Applying a wide range of phylogeographic methods including coalescent-based analyses we would like to reconstruct divergence processes and migration within and across species boundaries. Evidence for reticulate evolution and incomplete differentiation is provided by various accessions displaying extraordinary levels of chloroplast DNA polymorphism. We also want to assess the applicability of a phylogeographic approach to reconstruct mode and place of the origin of tetraploids. Distinctness of chloroplast lineages among tetraploid species which are similar in morphology, ecology and distribution suggests either a repeated origin with common underlying forces in establishment and spread, or substantial introgression of diploids towards tetraploids. Our results will allow general evaluation of the role of gene flow at different time scales during speciation processes in perennial self-incompatible herbaceous plants.