Evolution New Species of Whitefish Have Emerged in Every Lake

Researchers from Eawag - the Swiss Federal Institute of Aquatic Science and Technology, the University of Bern, and the Natural History Museum of Basel, came together to analyze 99 genomes of 22 whitefish species and concluded that the diversity of the species has arisen independently in each group of lakes since the last ice age partly due to their different depths and food sources.

Bern/Switzerland – Evolution can sometimes progress at an astonishing speed. The 24-plus whitefish species in the large perialpine lakes have all developed since the last ice age, i.e. over tens of thousands rather than millions of years. They differ not just in appearance and size, but also in terms of the depth, where they live and breed, as well as their preferred menu. Near the shore, the large "Balchen" feeds mainly on bottom-dwelling organisms, while in more open water the small "Albeli" feed on plankton, and the medium-sized "Felchen" feed on both. In the very deep lakes such as Thun, Lucerne and Constance, there are even more unusual species that live and spawn in open water or live at depths of more than a hundred meters.

Similar adaptations but different genomes

Led by Dr. Philine Feulner, a team from Eawag - the Swiss Federal Institute of Aquatic Science and Technology, the University of Bern, and the Natural History Museum of Basel, examined 99 genomes of 22 whitefish species and confirmed earlier hypothesis that this diversity has arisen independently in each group of lakes since the last ice age, partly as a result of adaptation to different depths and food sources. Particularly, the edar gene played a key role, which influences the gill-raker count and thus the "sieve density" when it comes to catching insects or plankton. But there were also thousands of other genes that had an impact, most of which were only important in a single lake. It is noteworthy that very different whitefish species from the same lake are still genetically more similar than species which, at first glance, may appear to be similar, but which have developed in parallel elsewhere.

Many species found only here

Genetic exchange within, but also between the larger lakes has led to hybridisation. This has favoured the emergence of unusual species and thus the large variety of endemic whitefish species seen in the perialpine lakes, i.e. species that are unique to this region.

Original publication: De-Kayne, R.; Selz, O. M.; Marques, D. A.; Frei, D.; Seehausen, O.; Feulner, P. G. D. (2022) Genomic architecture of adaptive radiation and hybridization in Alpine whitefish, Nature Communications, 13(1), 4479 (13 pp.), doi:10.1038/s41467-022-32181-8, Institutional Repository.

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