Evolution in real time: Scientists predict—and witness—evolution in a 30-year marine snail experiment
Snails on a tiny rocky islet evolved before scientists' eyes. The marine snails were reintroduced after a toxic algal bloom wiped them out from the skerry. While the researchers intentionally brought in a distinct population ...
The study, led by researchers from the Institute of Science and Technology Austria (ISTA) and the Norwegian Nord University, is published in Science Advances.
It is 1988. The Koster archipelago, a group of islands off the Swedish west coast near the border with Norway, is hit by a particularly dense bloom of toxic algae, wiping out marine snail populations. But why would anyone care about the fate of a bunch of snails on a three-square-meter rock in the open sea? As it turns out, this event would open up the opportunity to predict and see evolution unfolding before our eyes.
Before, the islands and their small intertidal skerries—rocky islets—were home to dense and diverse populations of marine snails of the species Littorina saxatilis. While the snail populations of the larger islands—some of which were reduced to less than 1%—were restored within two to four years, several skerries could not seem to recover from this harsh blow.
Marine ecologist Kerstin Johannesson from the University of Gothenburg, Sweden, saw a unique opportunity. In 1992, she re-introduced L. saxatilis snails to their lost skerry habitat—starting an experiment that would have far-reaching implications more than 30 years later.
Crab-ecotype snails (1992) evolved to strikingly resemble the lost Wave-ecotype snails on a skerry. Credit: ISTA, images by Kerstin Johannesson
The donor shore of the transplanted snail population (foreground) and the experimental skerry (little dot in the sea to the right). Credit: Kerstin Johannesson
Crab-ecotype L. saxatilis snails were brought here in 1992 after toxic algae wiped out the original Wave-ecotype population. Credit: Kerstin Johannesson