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  From gametes to species: Genetic and non-genetic effects in parasite-mediated selection

Kaufmann, J. (2015). From gametes to species: Genetic and non-genetic effects in parasite-mediated selection. PhD Thesis, Christian-Albrechts-Universität, Kiel.

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Kaufmann, Joshka1, Author              
Milinski, Manfred1, Referee              
Reusch, Thorsten B. H.2, Referee              
1Department Evolutionary Ecology, Max Planck Institute for Evolutionary Biology, Max Planck Society, ou_1445634              
2External, ou_persistent22              


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 Abstract: Parasites represent one of the most notable ecological forces acting in both natural and sexual selection. Their detrimental effects on host condition and reproductive success can have strong consequences on ecological and evolutionary dynamics. Particularly, host-parasite coevolution can lead to local adaptation which in turn can drive the evolution of reproductive barriers between populations and fuel speciation. As hosts are engaged in an arms race against ever-changing parasites, they rely on effective and consistent ways to transmit defenses to their progeny. The work of my thesis examines these two aspects from the host perspective. In my first two chapters I focused on the evolution of reproductive barriers in incipient ecological speciation in the three-spined stickleback (Gasterosteus aculeatus). I particularly examined the role of ecology and parasites in limiting gene flow and maintaining differentiation between lake and river stickleback populations. Following previous work in this system showing local adaptation and assortative mating preferences based on differences at the Major Histocompatibility Complex (MHC), I investigated further mechanisms of reproductive isolation: First, I tested if post-copulatory pre-zygotic reproductive barriers (e.g. gametic isolation) occurred during incipient ecological speciation between lakes and rivers. Using replicated populations and in vitro fertilization assays in a full-factorial design, I could demonstrate ecotype-specific differences in sperm concentration and velocity. Even though these differences did not translate into ecotypic gamete preference, the results suggest an increased developmental failure of the eggs fertilized by heterospecific males. This implies that genetic incompatibilities may arise early on during ecological speciation. In my second chapter I examined the role of immune local adaptation to parasites in selection against maladapted migrants. Using a field transplant experiment with wild-caught juvenile sticklebacks, I found strong costs of migration between habitats in terms of survival and condition. I could also show that differences in parasites between lake and river were linked to maladapted responses on the innate and the adaptive immune. Furthermore, evidence for habitat-specific associations between local parasite species and locally selected MHC alleles provided insight into the maintenance of MHC diversity at the metapopulation level. In my final chapter I examined another aspect of the role of parasites, namely the role of paternal non-genetic effects of infection on life-history traits, resistance and tolerance. Until recently, non-genetic transgenerational effects mostly focused on mothers, whereas this experiment demonstrated that infected fathers could also contribute to variation in offspring phenotype. I showed paternal effects of experimental parasite infection mediated through sperm deficiency. By testing and revealing costs and benefits associated with paternal infection and controlling for genetic factors, I provided evidence for the adaptive value of non-genetic transgenerational effects of infection. Furthermore, I showed that resistance and tolerance to parasites can be shaped by both genetic and non-genetic effects. I discuss that the existence of non-genetic effects increasing offspring tolerance but not resistance can have strong consequences on host-parasite dynamics at ecological and evolutionary scales. This thesis reveals the role of parasites in promoting and maintaining diversity in their hosts, from the level of the sperm phenotype to the species level. While gametic isolation plays a minor role in ongoing ecological speciation, local adaptation to different parasite communities leads to high costs of migration. My work additionally reveals that parasites can affect phenotypic variation not only within but also across generations.


Language(s): eng - English
 Dates: 2015-04-072015
 Publication Status: Published in print
 Pages: IV, 151 S.
 Publishing info: Kiel : Christian-Albrechts-Universität
 Table of Contents: -
 Rev. Method: -
 Identifiers: Other: Diss/12629
 Degree: PhD



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