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Université de Fribourg

Parasites promote host gene flow in a metapopulation

Altermatt, Florian ; Hottinger, Jürgen W. ; Ebert, Dieter

Local adaptation is a powerful mechanism to maintain genetic diversity in subdivided populations. It counteracts the homogenizing effect of gene flow because immigrants have an inferior fitness in the new habitat. This picture may be reversed in host populations where parasites influence the success of immigrating hosts. Here we report two experiments testing whether parasite abundance and...

Université de Fribourg

Ecological implications of parasites in natural Daphnia populations

Decaestecker, Ellen ; Declerck, Steven ; De Meester, Luc ; Ebert, Dieter

In: Oecologia, 2005, vol. 144(3), p. 382

In natural host populations, parasitism is considered to be omnipresent and to play an important role in shaping host life history and population dynamics. Here, we study parasitism in natural populations of the zooplankton host Daphnia magna investigating their individual and population level effects during a 2-year field study. Our results revealed a rich and highly prevalent community of...

Université de Fribourg

A high-density genetic map reveals variation in recombination rate across the genome of Daphnia magna

Dukić, Marinela ; Berner, Daniel ; Roesti, Marius ; Haag, Christoph R. ; Ebert, Dieter

In: BMC Genetics, 2016, vol. 17, p. 137

Recombination rate is an essential parameter for many genetic analyses. Recombination rates are highly variable across species, populations, individuals and different genomic regions. Due to the profound influence that recombination can have on intraspecific diversity and interspecific divergence, characterization of recombination rate variation emerges as a key resource for population...

Université de Fribourg

Benefits of host genetic diversity for resistance to infection depend on parasite diversity

Ganz, Holly H. ; Ebert, Dieter

In: Ecology, 2010, vol. 91, no. 5, p. 1263–1268

Host populations with high genetic diversity are predicted to have lower levels of infection prevalence. This theory assumes that host genetic diversity results in variation in susceptibility and that parasites exhibit variation in infectivity. Empirical studies on the effects of host heterogeneity typically neglect the role of parasite diversity. We conducted three laboratory experiments...

Université de Fribourg

Genotypic selection in Daphnia populations consisting of inbred sibships

Haag, Christoph ; Hebert, Dieter

In: Journal of Evolutionary Biology, 2007, vol. 20, no. 3, p. 881–891

The genetic basis of fitness reduction associated with inbreeding is still poorly understood. Here we use associations between allozyme genotypes and fitness to investigate the genetic basis of inbreeding depression in experimental outdoor populations of the water flea, Daphnia magna. In Daphnia, a phase of clonal reproduction follows hatching from sexually produced resting eggs,...

Université de Fribourg

Converging seasonal prevalence dynamics in experimental epidemics

Lass, Sandra ; Hottinger, Jürgen W ; Fabbro, Thomas ; Ebert, Dieter

In: BMC Ecology, 2011, vol. 11, p. 14

Background Regular seasonal changes in prevalence of infectious diseases are often observed in nature, but the mechanisms are rarely understood. Empirical tests aiming at a better understanding of seasonal prevalence patterns are not feasible for most diseases and thus are widely lacking. Here, we set out to study experimentally the seasonal prevalence in an aquatic host-parasite system. The...

Université de Fribourg

Host starvation decreases parasite load and mean host size in experimental populations

Pulkkinen, Katja ; Ebert, Dieter

In: Ecology, 2004, vol. 85, p. 823-833

While host stress in vertebrate populations has often been linked to outbreaks of epidemics, which are attributed to the immuno-compromise of the stressed hosts, no predictions have been made about the response of invertebrate host populations to stressful conditions. Experiments conducted on individual invertebrate hosts, however, suggest that starved hosts may be a poor resource for...

Université de Fribourg

Local adaptation of sex induction in a facultative sexual crustacean: insights from QTL mapping and natural populations of Daphnia magna

Roulin, Anne C. ; Routtu, Jarkko ; Hall, Matthew D. ; Janicke, Tim ; Colson, Isabelle ; Haag, Christoph R. ; Ebert, Dieter

In: Molecular Ecology, 2013, vol. 22, no. 13, p. 3567–3579

Dormancy is a common adaptation in invertebrates to survive harsh conditions. Triggered by environmental cues, populations produce resting eggs that allow them to survive temporally unsuitable conditions. Daphnia magna is a crustacean that reproduces by cyclical parthenogenesis, alternating between the production of asexual offspring and the sexual reproduction of diapausing eggs (ephippia)....