Many animal species are already on the edge of the abyss due to the loss of habitat and the fluctuations in temperature caused by the climate crisis. And many more will continue to be affected, but which ones will be able to adapt and survive climate change?
These fish have become a model of study for evolutionary biologists, thanks to their rapid adaptation to extreme seasonal changes in their habitat.
To answer this question, scientists try to predict which animals will best cope with rising temperatures and thus anticipate the evolutionary future of these populations. In a study, published in the journal Molecular Biology, researchers from McGill University in Canada have focused on the thorny (Gasterosteus aculeatus), a small fish, usually marine, native to Europe, North Asia and North America.
These fish, known for their different shapes, sizes and behaviors –Can live both in seawater as in sweet, and under a wide range of temperatures–, they have become a study model for evolutionary biologists, thanks to their rapid adaptation to extreme seasonal changes in their habitat.
“The biology of spiny fish is not fundamentally different from that of any other fish, but they do have a wide distribution that offers a large pool of permanent genetic variability that can allow adaptation when the environment changes. An example of this is when the populations were trapped in freshwater lakes after the last Glacial Maximum ”, he explains to SINC Alan Garcia-Elfring, from the Canadian university and lead author of the work.
Group of thorny trees. / Rowan Barrett
Natural selection in real time
To identify the genetic basis for these permanent adaptations and mutations, the scientists sequenced the genome thornbush and monitored six populations off the California coast, before and after seasonal changes in their environment. Thus the team was able to study the natural selection in real time.
Each year these estuaries are visited by a large influx of these marine fish that harbor different genetic variations depending on the populations. However, during the dry summer months, estuaries they are periodically closed and isolated from the ocean due to the formation of sandbanks. Even so, certain genotypes have been observed to increase in estuaries.
Our results suggest that the spiny tree adapts to the changing conditions of estuaries.
“Our results suggest that the thornbush adapts to the changing conditions of these mouths”, he indicates Garcia-Elfring. In reality, only fish capable of tolerating rapid changes in water temperature and salinity from season to season, with wet winters and dry summers, will be able to survive.
“These changes probably resemble the habitat changes that thorny populations experienced when they colonized many freshwater lakes newly created from the ocean after the retreat of glaciers 10,000 years ago,” says Rowan Barrett, co-author of the work and researcher in McGill University.
In this case, the genetic changes observed in fish have been driven by current seasonal changes, but they were already reflected in the differences found long ago between marine and freshwater populations. “These genetic changes occurred in independent populations in a single season, which shows how quickly the effects of natural selection can be detected”, confirms Alan García-Elfring.
For these scientists, the findings are important because they suggest that the evolutionary future of species and how species will adapt to environmental stressors, such as climate change, could be reliably predicted by understanding the historical genetic differences that have already evolved in the past. past.
To this end, the team underlines the importance of studying species in dynamic environments, such as estuaries, to better understand the functioning of natural selection, and thus check whether the observed genetic changes appear year after year.
Alan García-Elfring et al. “Using seasonal genomic changes to understand historical adaptation to new environments: Parallel selection on stickleback in highly ‐ variable estuaries” Molecular Biology
Rights: Creative Commons.