In: IAWA Journal, 2007, vol. 28, no. 1, p. 39-48
Due to the likelihood of global climate change, the frequency and magnitude of natural hazards such as mass movements may likewise change, thus favouring the refinement of methods to detect and quantify geomorphic events when precise records are not available. Geomorphic events typically have a significant effect on tree growth, e.g., reaction wood marked by changes in ring widths and wood...
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In: Behavioral Ecology and Sociobiology, 2006, vol. 61, no. 2, p. 291-304
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In: Biological Control, 2005, vol. 32, p. 269
Purple loosestrife, Lythrum salicaria, has invaded North American wetlands over the last 200 years. A biological control project was started in British Columbia, Canada, in 1993 with the introduction of Galerucella calmariensis, a leaf- feeding beetle of European origin. To evaluate the success of the biological control project in the Lower Mainland of British Columbia, we...
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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: 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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