Evolutionary dynamics and biodiversity: new discoveries from Europe's oldest lake

The researchers of the Department of Environmental Biology have taken part in a new international study which has highlighted how the ongoing climate changes are also a danger to an ancient and resilient ecosystem such as Lake Ohrid, a reservoir of biodiversity for our continent. The outcomes of the study which could have a strong impact for future research on biodiversity have been published on the journal Science Advances

An international research group led by Thomas Wilke of the Justus Liebig University of Giessen (Germany) in collaboration with Laura Sadori and Alessia Masi of the Department of Environmental Biology of Sapienza University of Rome, has shed new light on biological evolution using the deep sedimentary record of Lake Ohrid (on the border between Albania and North Macedonia). Ohrid, with a history of 1.4 million years and over 300 endemic species, is not only the oldest lake in Europe but also one of the richest in biodiversity. The results of the study have been published on the journal Science Advances.

In order to study the evolutionary dynamics of the lake since its formation, researchers have compared environmental and climatic data to the fossil finds of over 150 endemic species of diatoms (unicellular algae often present in lake deposits) found along the 568-metre long sedimentary sequence.

"Our data − says Alessia Masi of Sapienza − showed that shortly after the formation of the lake, and within a few thousand years, the first evolutionary events that quickly led to the formation of new species took place. Many of these species had a short life span, becoming extinct just as quickly when the lake was still relatively small and shallow."

The study highlights how "new" and small lakes offer great opportunities for speciation. On the other hand, these ecosystems are also particularly sensitive to environmental changes such as fluctuations in temperature, soil and lake level.

There has been a drastic decline in the rate of speciation and extinction as a result of the increase in the surface area and depth of the lake. This is due to the reduction in the number of new habitats, the high number of species, close to the maximum capacity of the environment and its resources, and the increasing capacity of the lake to mitigate the microclimate.

"The novelty of this work − concludes Laura Sadori of Sapienza − is that the ecosystemic history of Lake Ohrid, as told by a set of "ephemeral" species, i.e. evolutionary species of short duration but developed in a stable community of long-lived species, is actually rich in elements useful for understanding the biological evolutionary dynamics. That is why the outcomes of our study could have a strong impact also for future research on biodiversity."

References:

Deep drilling reveals massive shifts in evolutionary dynamics after formation of ancient ecosystem − Wilke T., Hauffe T., Jovanovska E., Cvetkoska A., Donders T., Ekschmitt K., Francke A., Lacey J.H., Levkov Z., Marshall C.R., Neubauer T.A., Silvestro D., Stelbrink B., Vogel H., Albrecht Ch., Holtvoeth J., Krastel S., Leicher N., Leng M.J., Lindhorst K., Masi A., Ognjanova-Rumenova N., Panagiotopoulos K., Reed J.M., Sadori L., Tofilovska S., Van Bocxlaer B., Wagner-Cremer F., Wesselingh F.P., Wolters V., Zanchetta G. , Zhang X., Wagner B. − Science Advances, 2020. DOI 10.1126/sciadv.abb2943