Abstract
Our aim is to identify the barriers to dispersal in two invasive microalgal species that form blooms in lakes and the Baltic Sea. Our approach is to determine the importance of physical versus biological dispersal barriers by analyzing the genetic diversity patterns. We hypothesize that physical dispersal barriers are important processes for generating genetic differentiation, but cannot alone account for the patterns observed, and that differentiation among microalgal populations might be explained by so called founder effects. Founder or priority effects refer to the dominance of strains or species that arrive first to a new habitat. These are enhanced by short generation time, rapid local adaptation of the resident population, and large propagule banks that buffer against new immigrants. In field studies we will study gene flow among populations that span across a range of geographic distance and hydrographic connectivity in the toxic marine Alexandrium ostenfeldii and the nuisance freshwater flagellate Gonyostomum semen. In laboratory and mesocosm experiments we will test priority effects and if invasion sequence matters. This research has implications for the understanding of the spreading of microalgae and microorganisms in general, as well as for predicting the occurrence of new algal blooms. Deliverables will include conceptual models and recommendations for targeted monitoring strategies, which will be designed in collaboration with authorities that are end users.
Sweden