Monitoring population and gene pool dynamics of the annual species Capsella bursa-pastoris (Brassicaceae): a review of relevant species traits and the initiation of a long-term genetic monitoring programme

Species that colonise habitats on an annual basis are important for studying and understanding evolutionary changes and adaptations in the course of environmental shifts, caused, for instance, by global change phenomena. These species are characterised by a weedy ecology enabling them to react fast to environmental changes. As a model species, we selected Capsella bursa-pastoris (Brassicaceae, Shepherd's Purse), which is annual to biennial, predominantly selfing and closely related to the genetic model plant Arabidopsis thaliana. Differentiation and adaptation in C. bursa-pastoris are shortly reviewed. Based on this knowledge, two Botanical Gardens are currently arranging long-term sites characterised by annual ploughing for the genetic monitoring of C. bursa-pastoris. Demographic parameters will be monitored as well, i.e. different life-cycle phases such as flowering, fruiting, and the soil seed bank. Furthermore, seeds of at least 20 individuals will be sampled per year. Isozyme analyses, flow cytometry, AFLPs, SNPs as well as microsatellites will be utilised to characterise changes in genetic diversity patterns over time. In general, the objective of our genetic monitoring of C. bursa-pastoris is to address the following questions: In the light of future research, our objectives are to study whether the genetic structure and diversity of C. bursa-pastoris alter over time, whether a possible invasion of ecotypes/genotypes of Sheperd's purse is traceable using genetic markers, and whether it is possible to relate variation in reproductive patterns to respective candidate genes, which may be useful for monitoring.