In 1988, the Koster archipelago off the Swedish west coast experienced a dense bloom of toxic algae that wiped out marine snail populations, particularly on small intertidal skerries. Marine ecologist Kerstin Johannesson saw an opportunity to reintroduce snails to their lost habitat in 1992, starting an experiment that would lead to the prediction and witnessing of evolution unfolding in real-time. This experiment involved an international collaboration between researchers from various institutions, including the Institute of Science and Technology Austria, Nord University, the University of Gothenburg, and The University of Sheffield.
The species of marine snails involved in the experiment, Littorina saxatilis, have different populations with traits adapted to their environments, such as size, shell shape, shell color, and behavior. Two distinct ecotypes of these snails are the Wave and Crab snails, which have evolved in different locations exposed to different environmental pressures. The Swedish Koster archipelago is home to both these ecotypes, with Wave snails inhabiting the skerries and Crab snails residing in nearby shores, often in close spatial proximity.
Following the toxic algal bloom that wiped out the Wave snail population on the skerries, Johannesson reintroduced Crab snails to the habitat in 1992. Over a span of 30 years, researchers observed the rapid and dramatic evolution of the transplanted Crab snails. Genetic diversity already present in the starting Crab population, coupled with gene flow from neighboring Wave snails, drove this evolution. The study examined changes in the snails’ phenotype, individual gene variabilities, and larger genetic changes affecting entire chromosomal regions, known as chromosomal inversions.
The researchers observed phenotypic plasticity in the snails, with rapid modifications in response to their new environment. They predicted the extent and direction of genetic changes, linking them to both selection of existing traits and gene flow from neighboring populations. This study highlights the importance of genetic diversity in enabling rapid adaptation to environmental changes and provides insight into how species can evolve in response to challenges like pollution and climate change.
The team’s findings shed light on how species can adapt to modern environmental challenges, emphasizing the importance of maintaining large and diverse genetic pools to facilitate adaptation. As the planet faces complex changes such as climate change, pollution, and habitat loss, understanding evolutionary processes and genetic variation becomes crucial for conservation efforts. By studying how species like the Littorina saxatilis snails evolve in response to environmental pressures, researchers hope to inform strategies for protecting biodiversity and preserving genetic diversity in natural habitats.
The experiment initiated by Johannesson in 1992 has led to a thriving population of around 1,000 individuals of the reintroduced Crab snails on the skerry. This long-term study has provided valuable insights into the mechanisms of evolution and adaptation in natural populations, highlighting the importance of genetic diversity in enabling species to respond to environmental changes. The researchers aim to continue studying how species adapt to evolving environmental challenges, contributing to the broader understanding of evolutionary processes and the conservation of biodiversity.