Karin Rengefors,
Professor

My research interests cover a variety of topics within phytoplankton/ protist ecology and evolution. Currently my research focus is on understanding the processes underlying speciation and biogeography in protists. My approach is to study these processes at the population level by investigating genetic diversity, population genetic structure, dispersal, and local adaptation. This research interest emerged from my PhD thesis work in which I studied the role of resting cysts to phytoplankton species and communities. I have also worked with competition among phytoplankton species, specifically allelochemical interactions.

Biogeography in protists: from species level to population level Whether or not microorganisms (including phytoplankton) exhibit biogeographic patterns and undergo allopatric speciation is debated, and there is both evidence showing endemism as well as cosmopolitan distribution. The processes and mechanisms generating biogeographies are closely connected to those regulating population genetic patterns. Processes at the population level (such as dispersal, generation of genetic diversity) as well as population genetic diversity are tightly connected to speciation events. Within four different projects, my collaborators and I are studying different aspects of this topic.

Crossing the salinity barrier – local adaptation, genetic divergence and speciation in microorganisms (Swedish Research Council) In this project we are investigating small-scale (< 10 km) genetic differentiation among lake populations of a marine/brackish dinoflagellates species Scrippsiella aff. hangoei. This species was previously considered endemic to the Baltic, but we have found a closely related species in saline Antarctic lakes located in the Vestfold Hills (Rengefors et al. 2008). In this same system we are studying salinity tolerance plasticity in the dinoflagellates species Polarella glacialis, which has a bi-polar distribution. This work is in collaboration with Dr. Ramiro Logares (Spain) and Dr. Johanna Laybourn-Parry (UK).

Another part of 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. 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. These studies are further pursued through the Marine Microbial Eukaryote Transcriptome Project funded by the Gordon and Betty Moore Foundation. This work is in collaboration with Dr. Ramiro Logares (Spain) and Dr. Anke Kremp (Finland).

Invasion patterns, genetic divergence, and barriers to dispersal (Formas) In two projects financed by the Swedish Research Council for Environment, Agricultural Sciences & Spatial Planning (Formas) we are investigating dispersal and population genetic structure in a potentially invasive freshwater phytoplankton species. The species, Gonyostomum semen, is known as a nuisance species that forms frequent and dense blooms in boreal lakes. My PhD student Karen Lebret has approached the problem on how and if it has dispersed using molecular markers and population genetic analyses.

In a second project the aim is to identify the barriers to dispersal in microalgal species that form blooms in freshwater lakes and the sea. 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. The project co PI is Dr. Anna Godhe (Gothenburg University).

Community metagenomics of Antarctic Protists – the importance of history versus environment. Dispersal and subsequent colonization of new habitats have important consequences for community composition. In order to study microbial communities it is imperative to know their taxonomic diversity. By the use of molecular techniques the diversity of protists has been shown to be much higher than what older methods indicated. A fundamental question is whether community composition of aquatic protists is a consequence of environmental filtering, mass effects, historical processes or a mix of the previous processes. In this project, marine and freshwater protist composition will be investigated in a lake metacommunity that includes marine-derived and glacial melt-water lakes (Vestfold Hills, Antarctica). These lakes operate very much as islands, imposing certain geographic limitations to populations, as well as dispersal among populations. The community composition will be analyzed using 454-sequencing technology. This project and associated postdoctoral fellow is part of the CanMove center.

Ongoing projects

2011-2013: Physical and biological dispersal barriers in invasive bloom-forming microalgae. Co-PI’s: Anna Godhe, Göteborg University, Anke Kremp, Finish Environment Institutes. Formas

2011: Marine Microbial Eukaryote Transcriptome Project. Gordon and Betty Moore Foundation

2010-2012: Crossing the salinity barrier – local adaptation, genetic divergence and speciation in microorganisms. The Swedish Research Council

2010: Predicting toxic algal blooms: a genomic approach. Co-PI: Rosa Isabel Figueroa. Crafoordska stiftelesen

2008-2010: Invasion patterns and dominance dynamics of a bloom-forming algae.Formas

Selected publications

Logares, R., Schalchian-Tabrizi, K., Bertilsson, S. Clasen, J., Bråte, J., Tranvik, L, & Rengefors, K. 2009. Infrequent marine-freshwater transitions in the microbial world. Trends in Microbiology. 17:414-422.

Kremp, A., Rengefors, K., Montresor, M. 2009. Species-specific encystment patterns in three Baltic cold-water dinoflagellates: The role of multiple cues in resting cyst formation. Limnology & Oceanography. 54:1125-1138.

Logares, R. Boltovskoy, A., Bensch, S., Laybourn-Parry, J. & Rengefors, K. 2009. Genetic diversity patterns in five protist species occurring in lakes. Protist. 160 (2):301-317.

Rengefors, K, , Pålsson, C., Hansson, L-A, Heiberg, L. 2008. Osmotrophy and cell lysis of competitors enhance the growth of the bloom-forming Raphidophyte Gonyostomum semen. Aquatic Microbial Ecology. 51: 87-96.

Rengefors, K., Laybourn-Parry, J., Logares, R., Mashall, W. A., & Hansen, G. 2008. Marine-derived dinoflagellates in Antarctic Saline Lakes: Community Composition and annual dynamics. Journal of Phycology 44 (3):341-349.

Logares, R., Schalchian-Tabrizi, Boltovskoy, A. & Rengefors, K. 2007. Extensive dinoflagellate phylogenies indicate infrequent marine-freshwater transitions. Molecular Phylogenetics & Evolution. 45: 887-903.

Logares, R., Rengefors, K. ,Kremp, A. , Shalchian-Tabrizi, K. , Boltovskoy, A., Tengs, T. , Shurtleff, A. , Klaveness. D. 2007. Phenotypically different microalgal morphospecies with identical ribosomal DNA: A case of rapid adaptive evolution? Microbial Ecology. 53(4):549-561.

Figueroa, R. I. & Rengefors, K. 2006. The life cycle and sexuality of Gonyostomum semen (Raphidophyceae). Journal of Phycology. 42: 859-871.

Anderson, D. M. & Rengefors, K. 2006. Community assembly and seasonal succession of marine dinoflagellates in a temperate estuary: The importance of life cycle events. Limnology & Oceanography. 51: 860-873.

Gustafsson, S., Rengefors, K., and Hansson, L-A. 2005. Increased consumer fitness following transfer of toxin tolerance to offspring via maternal effects. Ecology. 86:2561-2567.

Rengefors, K., Karlsson, I. & Hansson, L–A. 1998. Algal cyst dormancy – a temporal escape from herbivory. Proceedings of the Royal London Society B 265:1353-1358.

Rengefors, K. & Anderson, D. M. 1998. Environmental and endogenous regulation of cyst germination in two fresh-water dinoflagellates. Journal of Phycology 34 (4): 568–577.

Post-Doc host: Dr. Sylvie Tesson

PhD students, main advisor:
Karen Lebret Ingrid Sassenhagen

PhD students, assistant advisor:
Therese Jephson Johan Ahlgren

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