Sometimes evolution proceeds much more rapidly than we might think. Genetic analysis makes it possible to detect the earliest stages of species formation and to gain a better understanding of speciation processes. For example, a study just published in PLOS Genetics by researchers from Eawag and the University of Bern -- investigating rapid speciation in threespine stickleback in and around Lake Constance -- shows that a species can begin to diverge very rapidly, even when the two daughter species breed alongside one another simultaneously.
The innumerable three-spined stickleback which end up in fishermen's nets on Lake Constance are an unwanted by-catch. Unlike some other species, these tiddlers -- of no commercial value -- appear to be relatively unaffected by lake eutrophication, bank stabilization and channelization. This species has been spreading rapidly throughout the Swiss Central Plateau for around 150 years. Now, an elaborate genetic study conducted by researchers at Eawag and Bern University helps to explain the secret of its success: the stickleback can evidently adapt very rapidly to new habitats -- so rapidly that, for evolutionary biologists, it serves as a model for the divergence of a single species into two or more distinct species. Rather than just one "Lake Constance stickleback," the researchers found two different forms -- typical of the lake and of inflowing streams -- even though lake stickleback migrate into these streams during the spawning season.
According to first author David Marques, "It was completely unexpected for the species to diverge over such a short period, given that the sticklebacks breed at the same time and at the same sites." Usually, independent species develop by adapting to different habitats and reproducing isolated from other populations -- at different depths of a lake, for example. Among whitefish, different breeding and spawning seasons have additionally evolved.
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