Large and small scale evolutionary processes in the floodplain plant Cnidium dubium: From biogeography to population dynamics in fragmented river landscapes

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Cnidium dubium is a threatened river corridor plant species with a peculiar large and small scale distribution pattern. Due to this pattern, the species is predestined to shed light on both the biogeographical history since the last glacial period on the large scale as well as on the impacts of floodplain fragmentation by dykes on the small scale. The work related to the biogeographic history is already accomplished with evidence that the species could be a glacial relic. On the small scale we assume that hydrochory and disturbance processes are major factors shaping plant genetic patterns in dynamic river landscapes and that the fragmentation of floodplains by dykes has strong effects on plant population dynamics. With the proposed study, we want to test the hypotheses that the populations of the recent floodplain (still inundated in times of high water) show a higher clonal diversity as well as a lower genetic differentiation in comparison with those of the older floodplain (not flooded anymore) and that mainly in the recent floodplain genetic diversity increases from upstream to downstream populations. The goal is to contribute to a better understanding of the evolutionary processes of herbaceous plant species in response to river landscape alterations.