Genetic biodiversity
Biodiversity is a measure for the richness of life. The more species of living organism there are, the greater the biodiversity. But there is more to biodiversity than just the number of species – there is also diversity within a particular species. Think of all the different breeds of dog, for example. A Chihuahua, a Labrador, and a St Bernard all belong to the same species. Their different external features are caused by a number of genetic variations that have been created by selective breeding. But this doesn't just apply to breeds of dog – there is also genetic diversity within species in nature. Understanding genetic variation and the factors that influence it is thus an essential part of biodiversity research.
Erik Verheyen studies the population genetics of freshwater fish. “Genetic research is important for assessing how species and their populations are influenced by changes in their surroundings. This research has given us valuable information that can help to protect and preserve these species.”
A good example of this is the European bullhead, a small European freshwater fish that is found from Scandinavia to the South of Spain. Together with other scientists, Eric has studied European bullhead populations from a few Belgian rivers. He discovered that different genetic groups are to be found within this species in Belgium. One of these is found exclusively in the streams and rivers of the Schelde basin, while a second group is found in the Meuse basin. In the Steenputbeek stream, in the Scheldt region, the scientists discovered a third genetic group. “This was an unexpected find”, says Erik. “The bullheads in that one stream belong to a genetic group normally only found in Eastern Europe. It's unlikely that the animals could have swum all the way to this stream by themselves. We suspect that they travelled as stowaways with a cargo of trout that were set free into the Steenputbeek.”
Genetic research can also teach us something about the condition of a particular population. “We were also able to determine the condition of the European bullhead by calculating their length/weight ratio”, says Erik. “The heavier a fish of a certain length, the better its physical condition. This clearly showed that in populations with greater genetic variation, the bullhead on average were in better condition than in populations with low genetic variation. A decrease in genetic diversity can thus be a risk to the continued survival of a population.”
And that is precisely what is happening at the moment. Our rivers and streams contain many locks, dams, and other man-made constructions. These are impenetrable barriers for the European bullhead. Because of these many barriers, populations are becoming more and more separated from each other, and above all, diminishing in size. There is less genetic diversity in smaller populations, and so the condition and fertility of the bullhead will deteriorate. Today, the European bullhead is thus a threatened species in Belgium.
“The story of the European bullhead is also relevant to dozens of other fish species”, says Erik. “But thanks to genetic research, we know which populations are in danger and we can determine in which areas we need to intervene, by building fish ladders for example. These are special passages that allow the fish to swim through the barriers, thus counteracting the shrinking of populations.”
