In: Parasitology, 2005, vol. 130, p. 501
Periods of low host density impose a constraint on parasites with direct transmission, challenging their permanence in the system. The microsporidium Octosporea bayeri faces such constraint in a metapopulation of its host, the cladoceran Daphnia magna, where ponds frequently lose their host population due to ponds drying out in summer and freezing in winter. We conducted experiments aimed to...
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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...
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In: Journal of Evolutionary Biology, 2004, vol. 17, p. 1402-1404
Salathé and Ebert (2003, J. Evol. Biol. 16: 976-985) have shown that the mean logarithmic fitness of Daphnia magna clones declined faster than linearly with increasing inbreeding coefficient F. They interpreted this result as evidence for synergistic epistasis. Trouve et al. (2004, J. Evol. Biol., doi: 10.1111/j.1420-9101.2004.00755.x) suggested that hybrid vigour could be an alternative...
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In: Journal of Molecular Evolution, 2004, vol. 59, p. 90-96
Reduction of genome size and gene shortening have been observed in a number of parasitic and mutualistic intracellular symbionts. Reduction of coding capacity is also a unifying principle in the evolutionary history of mitochondria, but little is known about the evolution of gene length in mitochondria. The genes for cytochrome c oxidase subunits I–III, cytochrome b, and the large and small...
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In: Limnology and Oceanography, 2004, vol. 49, no. 4, p. 1355-1364
Microparasites and epibionts have important implications for the ecology and evolution of their zooplankton host populations. Many parasites and epibionts produce resistant spores that infect new hosts upon intake. We explored the hypothesis that these spores build up dormant stage banks that remain infective for several years (decades). In laboratory experiments, we exposed Daphnia magna to...
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In: Parasitology, 2004, vol. 128, p. 31-38
The fresh-water crustacean Daphnia magna may acquire an infection with the microsporidium Octosporea bayeri either by ingesting spores from the water (horizontally), or directly from its mother (vertically). Due to differences in the time and mechanisms of transmission, horizontal and vertical infections may lead to differences in the growth of the parasite within the host. This may influence...
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In: Proceedings of the Royal Society of London: Biological Sciences, 2004, vol. 271, p. 2149-2155
In metapopulations, only a fraction of all local host populations may be infected with a given parasite species, and limited dispersal of parasites suggests that colonization of host populations by parasites may involve only a small number of parasite strains. Using hosts and parasites obtained from a natural metapopulation, we studied the evolutionary consequences of invasion by single strains...
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In: Proceedings of the Royal Society of London: Biological Sciences, 2004, vol. 271, p. 1175-1183
Estimates of phenoloxidase (PO) activity have been suggested as a useful indicator of immunocompetence in arthropods, with the idea that high PO activity would indicate high immunocompetence against parasites and pathogens. Here, we test for variation in PO activity among clones of the planktonic crustacean Daphnia magna and its covariation with susceptibility to infections from four different...
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In: Annales Zoologici Fennici, 2004, vol. 41, no. 4, p. 539-544
In many plants and animal species, asexuals are more common in marginal habitats such as high latitudes or altitudes than their closely related sexual counterparts. Here we propose a new hypothesis to explain this pattern called "geographic parthenogenesis". In marginal habitats, populations may often exist as metapopulations with high degrees of subdivision and local extinction and ...
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In: Ecology Letters, 2004, vol. 7, p. 1225-1241
Studies of local adaptation provide important insights into the power of natural selection relative to gene flow and other evolutionary forces. They are a paradigm for testing evolutionary hypotheses about traits favoured by particular environmental factors. This paper is an attempt to summarize the conceptual framework for local adaptation studies. We first review theoretical work relevant for...
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