Background/Question/Methods:
Studies increasingly reports rapid and adaptive evolution. Given the ubiquity of strong, often anthropogenic, changes in environmental conditions, there is growing awareness that micro-evolutionary dynamics may alter ecological processes. The “monopolization hypothesis” predicts that genetic adaptation to local conditions may strengthen priority effects. Whereas this hypothesis was originally formulated to explain patterns of differentiation at the intraspecific level, its prediction of enhanced priority effects mediated by local adaptation can be extrapolated to community assembly. We tested several predictions of the monopolization hypothesis experimentally, using zooplankton as a model system. In earlier work, we have shown that genetically different populations of a strong competitor, the waterflea Daphnia magna, can have a different impact on the establishment success of immigrants of the regional species pool. In an effort to directly assess the impact of local adaptation on establishment success of immigrants, we here combine an approach of experimental evolution with subsequent monitoring of the establishment success of standardized inoculate of species and genotypes. We allowed genetically diverse Daphnia magna populations to adapt to well-defined conditions (presence and absence of fish; temperature regimes) in out-door containers, and monitored the process of local genetic adaptation. Then, containers with either locally adapted or non-adapted populations were, depending on the experiment, inoculated with either a sample containing a diverse zooplankton assemblage, or a sample consisting of well-defined genotypes of the same species.

Results/Conclusions :
We observed significant evolutionary changes in only a few months in ecologically relevant traits in both the experiment using different predator regimes (intrinsic rate of natural increase) as well as in the experiment using different temperature regimes (size at maturity). Subsequent to both experiments, establishment success of immigrant communities and genotypes was monitored for locally-adapted and non-adapted populations. So far, we obtained results from a subset of these experiments. These results indicate that, in the predator experiment, the relative abundance of Daphnia magna in the resulting communities was higher in the treatments with locally adapted than in the treatments with non-adapted populations. In the climate change experiment, we confronted UK populations with immigrant genotypes from France and Spain, and observed that UK populations that were allowed to adapt to higher temperature during several months had higher relative fitness in competition with southern immigrant genotypes than non-adapted populations. Overall, our results indicate that local adaptation indeed influences establishment success of immigrant species and genotypes, while at the same time variation among experiments and treatments was high.