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Evolution more rapid than Darwin thought
22 March 2010
Evolution can proceed much more rapidly than has long been thought. This is shown by Magnus Karlsson, a doctoral candidate at Linnaeus University in Kalmar, in his dissertation about the impact of genetics and the environment on the color patterns of pygmy grasshoppers.
It has been the accepted view among evolutionary biologists since Darwin published his Origin of Species in 1859 that measurable evolutionary changes occur slowly, often taking hundreds of generations. This view may now be about to change.
Pygmy grasshoppers exist in many different color variants and in many types of environment. Through a series of experiments and studies in nature, Magnus Karlsson discovered that the distribution between the color variants of pygmy grasshoppers differs across different environments. In recently burnt over areas, a very high proportion of the grasshoppers are black. In unburnt areas, on the other hand, the black variant is unusual. What’s more, the proportion of black grasshoppers changes very rapidly between generations in the burnt areas, whereas the proportion in unburnt areas remains the same over the same period of time.
Magnus Karlsson presents data that show that the pygmy grasshoppers’ color changes by natural selection. He believes that the primary cause of these changes is birds and other animals that hunt using their vision. The black grasshoppers are simply less visible against the burnt background, so they survive more often. But as the environment changes and becomes more complex, the advantage of being dark diminishes, and other color variants can once again increase in number.
In his experiments, Magnus Karlsson has also shown that the color pattern of the pygmy grasshopper is genetically conditioned and is passed on from parent to offspring. On the other hand, various environmental factors, such as crowdedness or the substrate the grasshoppers grow up on, do not affect their color. In other words, there is no indication that the grasshoppers themselves can change their color depending on what environment they are surrounded by. Therefore, the great differences that exist between burnt and unburnt environments are the result of unusually rapid evolutionary change.
But it is not only that evolution sometimes proceeds rapidly; variation itself also offers major advantages. In groups consisting of many different color variants, survival is higher than in groups with less color variation. This means quite simply that variable groups may find it easier to adapt to environmental changes and that they are more productive.
The practical significance of Magnus Karlsson’s discoveries is broad and just as varied as his grasshoppers. He believes this new knowledge can be used in planning preservation projects for threatened species and to improve yields in agriculture.
“But the most important part of the dissertation is that I have shown that evolution sometimes proceeds incredibly rapidly. This is huge,” says Magnus Karlsson.
His dissertation is titled Evolution in Changing Environments Revealed by Fire Melanism in Pygmy Grasshoppers.