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Biogeography in protists

Drivers of genetic differentiation in protist populations


This project is focused on the speciation event that has resulted in the formation of the two separate species Scrippsiella hangoei (marine) and Peridinium aciculiferum (freshwater) (Logares et al. 2008). We are investigating both genetic divergence and reproductive barriers between these two, and the sibling species S. aff. hangoei in the Antarctic lakes, as well as two closely related freshwater species. Our previous studies indicate that salinity is a major barrier to speciation (Logares et al. 2008, 2009, 2010). Therefore, we are particularly interested in the response to salinity and differentiation at both the genetic and expression level. A population genomic approach (RAD-sequencing) is used to detect regions of selection and potential genes involved, in tandem with analyses of phenotypic variation of potential adaptive traits. In addition we are analyzing the transcriptomes of these species through the Marine Microbial Eukaryote Transcriptome Project funded by the Gordon and Betty Moore Foundation.

Physical and biological dispersal barriers in invasive bloom-forming microalgae


In this project financed by the Swedish Research Council for Environment, Agricultural Sciences & Spatial Planning (Formas) we are investigating the invasive freshwater phytoplankton species, Gonyostomum semen. This species is known as a nuisance species that forms frequent and dense blooms in boreal lakes. In previous work we have analyzed its population genetic structure, which supported the hypothesis of a recent expansion. Nevertheless, populations are genetically differentiated. The aim of the current project is to identify the barriers to dispersal in microalgal species that form blooms in freshwater lakes and the 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 are studying 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 experiments we are testing priority effects and if invasion sequence matters as well as phenotypic diversity. 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. The approach is to determine the importance of physical versus biological dispersal barriers by analyzing the genetic diversity patterns.

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People involved

Drivers of genetic differentiation in protist populations

Physical and biological dispersal barriers in invasive bloom-forming microalgae

Other lab members

Collaborators

Drivers of genetic differentiation in protist populations

  • Nataliia Annenkova (Russia)
  • Dr. Anke Kremp (Finland)

Physical and biological dispersal barriers in invasive bloom-forming microalgae

  • Josefin Sefbom, Gothenburg University
  • Anna Godhe, Gothenburg University
  • Kerstin Johanesson, Gothenburg University

Funding

Drivers of genetic differentiation in protist populations

Swedish Research Council

Physical and biological dispersal barriers in invasive bloom-forming microalgae

Formas