The human factor on natural selection Artificial selection can be unintended, where human activities have affected wild populations in ways that were not foreseen. Professor Claus Wedekind and his colleagues are investigating whether natural populations of salmonids have the evolutionary potential to adapt to the presence of different stressors in their environment. Artificial selection has long been used by humans to breed crops and animals like cows, sheep and fish with specific traits that will then be passed on to the next generation, traits which may make them more attractive to consumers. Alongside intended artificial selection, there are also cases of unintended artificial selection, where human activities have affected wild populations in ways that were not anticipated. “For example, there is selection by pollution or climate change, or by non-random harvesting. Lots of human activities can create new forms of selection on natural populations,” explains Claus Wedekind, a Professor in the Department of Ecology and Evolution at the University of Lausanne. In his research, Professor Wedekind is studying the evolution of natural populations in today’s environments, which are very much influenced by human activities. “If human activities lead to pollution in a river for example, and the fish in this river have genetically-based differences in their tolerance towards the pollution, then we predict that the pollution will change the allele frequencies in that fish population over time,” he outlines.
Allele frequency This will lead to evolution, which can be broadly summarised as change in allele frequency over time, a topic which lies at Freshly caught whitefish (Coregonus suidteri).
the heart of Professor Wedekind’s work as the lead of an SNF-funded research project. One question that Professor Wedekind and his colleagues in the project are studying is whether a given population of fish has the potential to adapt to a changing environment. “We study fish in Switzerland which belong to the salmonid family, such as grayling and brown trout,” he says. This work involves studying natural populations of fish through a combination of field observations and laboratory experiments, with the aim of building a fuller picture of how they are
We want to see whether the change in allele frequencies can be somehow linked to the level stressors. This is about quantitative genetics. changing. “We sample breeding fish from the wild, so males and females from the spawning location. We measure their phenotypes and take a tissue sample to study their genetics then we use their gametes - their eggs and sperm - for in vitro fertilization. It’s fairly easy to collect eggs and sperm,” explains Professor Wedekind. “Then we do experimental breeding. We take a sample of these families, bring them to the laboratory, and test them for their stress tolerance under very controlled experimental conditions.” Setting the gill nets.
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The aim here is to expose the fish to certain things that have been identified as relevant, such as the drugs that are regularly found in streams and rivers in Switzerland. One prominent example is ethinylestradiol, a synthetic oestrogen that’s used in contraceptive pills and is known to be toxic to fish; it cannot be broken down by wastewater treatment plants so it can seep into ecosystems. “Ethinylestradiol is a stressor, a pollutant that has been around for sixty years – and here we can test whether we see signs of adaptation to it in certain fish populations,” outlines Professor Wedekind.
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The fish are exposed to ecologically relevant concentrations of ethinylestradiol and other drugs, essentially replicating natural conditions in the laboratory. “We consider everything that we believe could be ecologically relevant, such as changes in temperature. We test these factors in the laboratory on a sub-set of the family at concentrations or levels that have this ecological relevance,” continues Professor Wedekind. “The rest of the family is raised by wildlife managers in hatcheries, and then released into the wild at different stages.” Juvenile brown trout (Salmo trutta).
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