The alpine flora is extraordinarily rich in species. Many species are endemic and perfectly adapted to the nasty conditions of the mountains. For hundreds of years, researchers have been puzzling over how and when the flora in the Alpine region acquired its biological diversity.
An international research team with the participation of the ecologist Niklaus Zimmermann from the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) is now giving an “unprecedented insight into the history of the diversification” of the alpine mountain flora, as the study published on Wednesday says.
Contrary to previous assumptions, the alternating cold and warm periods of the Pleistocene, which began around 2.5 million years ago and ended 12,000 years ago, did not lead to a sharp slowdown in diversification. Rather, during these climate changes, mountain plants began to conquer new niches, forming new species. According to the researchers, this counteracted extinction events at high altitudes during the glacial periods.
The mountain flora adapted to the cold, which is native to the Alps today, has its origins in the Himalayas. From there the plants spread to the mountains of the world and diversified.
According to the study, the diversification of high mountain plants was not driven by individual geological or climatic influences, but rather three factors played a decisive role in speciation: geographical barriers that isolated the plants for a sufficiently long period of time, migration to lower or higher altitudes, probably triggered by climate fluctuations , as well as the colonization of different rock types with subsequent speciation.
The latter in particular played a more important role than previously assumed, said Zimmermann in an interview with the Keystone-SDA news agency. For example, many plants migrated from siliceous rock to calcareous rock and vice versa during speciation. However, there were more net shifts from silicate to calcareous, consistent with observations that the calcareous mountain flora tended to be more species-rich than that colonizing silicate rocks. The reason for this has not been finally clarified, said the WSL researcher.
In the past millions of years, processes of extinction and the formation of new species alternated again and again. A study published in the journal Nature in 2018 showed that mountaintop biodiversity across Europe is increasing as global warming progresses, and that this is happening at an accelerating rate. Significantly more plant species grow on mountain peaks today than 100 years ago. Because warmth-loving species from lower altitudes are increasingly succeeding in penetrating higher regions where they could not survive before.
However, this is accompanied by the danger that the traditional mountaineers will be displaced and die out. Because: “In the short term, the cold-loving species will not be able to adapt to the new conditions, they will need thousands to millions of years to do so,” said Zimmermann. But in the long term it is quite possible that new species would form.
However, the current warming is extremely rapid compared to the history of the earth, which should exacerbate the extinction process and therefore open up more free niches. According to Zimmermann, it will take longer to repopulate these unoccupied niches due to the very slow evolutionary processes.