Current main research topics
My group works in the interface of ecology, evolution and health of aquatic ecosystems.
Evolutionary ecology of multiple parasite species/genotype infections
One of the main research areas focuses on evolutionary ecology of multiple species/genotype infections in host-parasite interactions. We are particularly interested in exploring how parasite species and genotypes interact in hosts, and how this affects factors such as parasite infection success and virulence. We also investigate how responses of the hosts are influenced by a diverse parasite challenge and how dynamics of host immune function shape parasite-parasite interactions. These studies look also into broad scale patters of genotype and species interactions underlying parasite community structure.
We explore these questions using mainly trematodes of the genus Diplostomum that complete their complex life cycle by passing through three consecutive hosts: snail and fish intermediate hosts, and bird definitive host. Infection in the snail gives rise to thousands of genetically identical cercariae that infect eye lenses of freshwater fishes. Severe infection in the eye may result in cataracts that impair vision and alter the behaviour of fish.
Seppälä, O., Karvonen, A., Rellstab, C., Louhi, K.-R., Jokela, J. (2012). Reciprocal interaction matrix reveals complex genetic and dose-dependent specificity among coinfecting parasites. American Naturalist, in press.
Karvonen, A., Rellstab, C., Louhi, K.-R., Jokela, J. (2012). Synchronous attack is advantageous - mixed genotype infections lead to higher infection success in trematode parasites. Proceedings of the Royal Society B 279, 171-176.
Rellstab, C., Louhi, K.-R., Karvonen, A., Jokela, J. (2011). Analysis of trematode parasite communities in fish eye lenses by pyrosequencing of naturally pooled DNA. Infection, Genetics and Evolution 11, 1276-1286.
Karvonen, A., Seppälä, O., Valtonen, E.T. (2009). Host immunisation shapes interspecific associations in trematode parasites. Journal of Animal Ecology 78, 945-952.
Parasites and aquatic biodiversity
We are also interested in interactions between parasitism, and ecological and genetic divergence in populations of freshwater fishes. This work includes investigations into patterns of parasitism in allopatric, parapatric and sympatric ecotypes of fishes, further linking these to the degree of between-population divergence in ecological characteristics and genetic profiles. The main study species include European populations of three-spine stickleback, Arctic charr and whitefish.
These projects are done in collaboration with Prof. Ole Seehausen and Prof. Jukka Jokela (Eawag, Switzerland), Prof. Skuli Skulason and Dr. Bjarni Kristjansson (Holar University College, Iceland) and Dr. Christophe Eizaguirre (IFM-GEOMAR, Kiel),
Karvonen, A., Lundsgaard-Hansen, B., Jokela, J., Seehausen, O. (2012). Differentiation in parasitism among ecotypes of whitefish segregating along depth gradients. Oikos, in press.
Karvonen, A., Seehausen, O. (2012). The role of parasitism in adaptive radiations – when might parasites promote and when might they constrain ecological speciation? International Journal of Ecology, Vol. 2012, Article ID 208169.