DR BARBARA TSCHIRREN
HOST-PARASITE INTERACTIONS
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I am fascinated by coevolutionary processes in host-parasite systems, how parasites drive the evolution of host behaviour, life history evolution and population dynamics and which strategies hosts adopt to reduce the parasite impact. Using the great tit, a small hole-breeding passerine, and its most common ectoparasite, the hen flea, I experimentally investigate
- why males and females differ in their parasite susceptibility,
- what are the costs and benefits of investment in immunological parasite defence, and
- which hosts are tasty for the parasites.
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Collaboration: Dr Patrick Fitze (Museo Nacional de Ciencias Naturales, Madrid, Spain); Prof Heinz Richner, Linda Bischoff & Verena Saladin (University of Bern, Switzerland)
ADAPTIVE MATERNAL EFFECTS
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Maternal effects are a flexible mechanism by which females can adjust the phenotype of the offspring to the current environmental conditions. My work mainly focuses on how maternal effects mediated by differential allocation of yolk androgens into the eggs can shape coevolutionary processes in host-parasite systems (see above). Numerous studies have shown that maternal yolk hormones have beneficial effects for the offspring in terms of higher growth rates, higher competitiveness in the nest and a higher social status after fledging. However, the cost of exposure to high yolk androgen concentrations are less well understood. I experimentally investigate if
- exposure to high yolk androgen concentrations during embryonic development is costly in terms of higher parasite susceptibility and lower immunocompetence of the nestlings
- if females adaptively adjust the allocation of yolk hormones into the eggs in relation to parasite abundance
Current work looks at patterns of maternal yolk hormone deposition in different passerine species and the role of maternal yolk hormones in shaping offspring dispersal. I recently also started a collaborative project on the effects of maternal antibodies on parasite susceptibility and parasite fitness in the great tit-flea system.
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Collaboration: Maternal yolk hormones: Dr Blandine Doligez (University of Lyon, France), Prof Ton Groothuis (University of Groningen, Netherlands), Prof Heinz Richner (University of Bern, Switzerland), Prof Hubert Schwabl (Washington State University, USA); Maternal antibodies: Dr Heli Siitari (University of Jyvaskyla, Finland)
THE EVOLUTION AND SIGNALLING FUNCTION OF CAROTENOID-BASED COLOURS
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Many taxa show elaborate colour traits, which contain information about the quality of an individual. To understand the evolution of such exaggerated colour traits and their information content, we need to know the mechanisms that determine variation in colour expression and the function of the colour in social interactions. I am especially interested in the yellow breast colour of great tits, one of the few bird species that show carotenoid-based plumage coloration already during the nestling stage. Since juveniles moult their body plumage before their first reproduction, it is unlikely that this colour trait evolved in the context of sexual selection (as most other carotenoid-based ornaments). I experimentally investigate,
- which factors determine the expression of the carotenoid-based coloration,
- if there is a trade-off in the investment of rare carotenoids in immune defence and colour expression,
- what is the signalling function of the carotenoid-based nestling coloration in parent-offspring interactions and
- what are the short- and long-term selection pressures acting on nestling- and adult plumage colour.
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Collaboration: Dr Patrick Fitze (Museo Nacional de Ciencias Naturales, Madrid, Spain)
MY CURRENT PROJECT
I recently moved to the University of New South Wales to work on wild
Zebra finches. This project will focus on variation in mate preference and choosiness among females and how this variation affects offspring performance.
