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Host-parasite interactions in hybridizing Daphnia, the role of variable environments

Titel Englisch Host-parasite interactions in hybridizing Daphnia, the role of variable environments
Gesuchsteller/in Spaak Pieter
Nummer 116470
Förderungsinstrument Projektförderung (Abt. I-III)
Forschungseinrichtung Eawag
Hochschule Eidg. Anstalt für Wasserversorgung, Abwasserreinigung und Gewässerschutz - EAWAG
Hauptdisziplin Oekologie
Beginn/Ende 01.08.2007 - 30.09.2010
Bewilligter Betrag 268'668.00
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Alle Disziplinen (3)


Keywords (6)

hybridization; host-parasite-interaction; evolution; population genetics; zooplankton; lakes

Lay Summary (Englisch)

Lay summary
BACKGROUND - Host-parasite reactions have been studied in only a limited number of animal hybrid systems, this in contrast to plants. The present theory states that hybrids are either more susceptible as the parental species, intermediate or less susceptible. For all three hypothesis examples have been found in different animal systems. However, an overall framework or theory that explains all these observations does not exist.Recent studies on host-parasite interactions have shown the importance of the environment for the outcome of this kind of interaction. First it was found that specific host genotypes are infectable at certain temperatures but not at others. Secondly it was shown that virulence of parasites is in general strongly temperature dependent.In our work on Daphnia (water flea) in hybrid systems we observed that not always the same parental or hybrid taxon is more susceptible, but that this pattern differs between seasons and lakes. This gives strong suggestions that the interaction between hybrid taxa and parasites is not a static but a dynamic feature. With the research we propose here we want to test experimentally hypotheses which we have formulated based on our field observations and recent literature findings. Moreover, using existing and new molecular markers we want to show how genetic variation among host and parasite changes in time.RESEARCH QUESTIONS - With the research proposed here we want to test the hypothesis that environmental variation significantly influences the outcome of host-parasite interactions. Furthermore we hypothesize that the differences we observe in infection level among eutrophic (nutrient rich) and oligotrophic (nutrient poor) lakes are caused by conditions of these lakes and not by the genetic composition of the host. Our third important working hypothesis is that the parasite adapts to the most common taxon in the lake, as would be predicted by the Red Queen Hypothesis. This parasite evolution we want to document using molecular markers.METHODS - We want to test the hypotheses mentioned above using the water flea Daphnia galeata - cucullata - hyalina hybrid system. These Daphnia species occur in different combinations of parental species and hybrids in almost all European lakes. As parasite the protozoan gut parasite Caullerya mesnili will be used. Infections will be done with a spore mix collected from infected animals collected from the field. The influence of changing environment (over the last decades) on host-parasite interactions will be studied in Greifensee, by investigating resting stages from host and parasite which are archived in the sediment. Also the temporal genetic variation of the host-parasite interactions will be monitored in this lake.
Direktlink auf Lay Summary Letzte Aktualisierung: 21.02.2013

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