Deep drilling in Europe's oldest and most species-rich lake provides new insights into evolution
The older and more stable an ecosystem is, the longer lived its species and the more stable the species communities are. An international research team led by the Justus Liebig University Giessen and the University of Cologne with participation of the Department of Paleontology, Stratigraphy and Sedimentology from Geological Institute "Strashimir Dimitrov", Bulgarian Academy of Scences, gained these new insights into evolution by drilling deep into the sediments of Lake Ohrid. The 1.4 million year old lake on the border between Albania and Northern Macedonia is not only the oldest lake in Europe, but with more than 300 endemic species, i.e. species that only occur there, it is also the most species-rich.
To study the evolutionary dynamics of Lake Ohrid since its formation, the scientists combined the environmental and climate data of a 568-meter-long sediment core with the fossil records of over 150 endemic diatom species. The data showed that shortly after the formation of the lake, new species emerged within a few thousand years. Many of them died out again very quickly in the relatively small and shallow lake. The research team explains this by the fact that young lakes of small size offer many new ecological opportunities, but are also particularly sensitive to environmental changes such as fluctuations in temperature, lake level and nutrients.
After the lake became deeper and larger, the speciation and extinction processes slowed down dramatically. The scientists attribute this to fewer new habitats emerging, the species richness approaching an ecological carrying capacity and an increasing environmental and climate buffering of the lake. The finding that in the history of Lake Ohrid, a volatile assemblage of evolutionarily short-lived species developed into a stable community of long-lived species provides a new understanding of the evolutionary dynamics in ecosystems. The study, which has now been published in the journal “Science Advances”, will thus also have great significance for future biodiversity research.
Our results show that ecosystems become more stable with increasing age and size and are better able to cope with natural climate fluctuations," says lead scientist Prof. Dr. Thomas Wilke. "But that doesn't mean that they can't reach a tipping point”. With regard to the drastic environmental and climate changes caused by humans, he added: "Not only the unique ecosystem of Lake Ohrid is endangered if the environment changes too quickly and too strongly".
Wilke et al. (2020): Deep drilling reveals massive shifts in evolutionary dynamics after formation of ancient ecosystem. Science Advances, 6, eabb2943. doi.org/10.1126/sciadv.abb2943
The 1.4 million year old Lake Ohrid on the border between Albania and Northern Macedonia (Photo credit: Thomas Wilke)
Drilling platform for deep drilling in Lake Ohrid (Photo credit: Thomas Wilke)
Colorized scanning electron microscope image of the endemic diatom species Scoliodiscus glaber from Lake Ohrid. Size of the silica shell 0.1 mm (Photo credit: Z. Levkov)