Parasites promote host gene flow in a metapopulation |
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Authors: | Florian Altermatt Jürgen Hottinger Dieter Ebert |
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Institution: | 1.Zoologisches Institut,Universit?t Basel,Basel,Switzerland;2.Département de Biologie, Unité d’Ecologie et Evolution,Université de Fribourg,Fribourg,Switzerland;3.Tv?rminne Zoological Station,Hanko,Finland |
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Abstract: | 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 genetic background influences the success of host migration among pools in a Daphnia magna metapopulation. In 22 natural populations of D. magna, immigrant hosts were found to be on average more successful when the resident populations experienced high prevalences of
a local microsporidian parasite. We then determined whether this success is due to parasitism per se, or the genetic background
of the parasites. In a common garden competition experiment, we found that parasites reduced the fitness of their local hosts
relatively more than the fitness of allopatric host genotypes. Our experiments are consistent with theoretical predictions
based on coevolutionary host-parasite models in metapopulations. A direct consequence of the observed mechanism is an elevated
effective migration rate for the host in the metapopulation. |
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Keywords: | Immigration Local parasite Metapopulation Coevolution Daphnia magna Octosporea bayeri |
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