In a recent paper, Professor Kari Saikkonen and his team present a theory that the distinct light environments of the polar regions contribute to the creation of hybrid zones. The seasonal extremes of light - 24-hour daylight during the summer and months of Polar Night in winter - cause species to synchronize their reproduction. "At the centre of our theory is the hypothesis that the extreme light environment of the polar regions creates hybrid zones in both polar regions," says Saikkonen.
This synchrony is particularly important for species relying on light, such as plants and microbes, which use changes in day length as a signal for reproduction. The overlap in flowering times promotes hybridization, where different species or varieties reproduce together, possibly increasing genetic diversity. Hybridization is common in various organisms and can allow gene exchange between species, creating new adaptive combinations suited to varying environments.
At lower latitudes, where seasonal day length changes are less extreme, hybridization is less frequent. But in polar regions, the unique light conditions encourage overlapping reproductive periods, creating opportunities for hybridization. "Species' range shifts across latitudes during the cycles of the Earth's cooler and warmer periods cause recurrent isolation and contact among species. This results in mixing and differentiation of species and creates new biodiversity over long periods of geological time," says Saikkonen.
Microbial Role in Polar Adaptation and Biodiversity
Microbes, which have influenced biodiversity since the origin of life, also play a key role in sustaining and promoting biodiversity today. According to Saikkonen, microbes are light-sensitive and can help plants adapt to polar environments, a factor crucial for maintaining ecosystems in these regions. "Microbes are ubiquitous, and mounting evidence continues to reveal that they have high adaptive potential due to their short life cycle. Many microbes are light sensitive and affect the well-being of virtually all plants and animals. Since all plants and animals have a diverse microbiota, they should be treated as a whole," notes Saikkonen.
Impacts of Climate Change on Polar Biodiversity
The Earth's polar regions are particularly vulnerable to climate change, which is warming these areas 2 - 4 times faster than the global average. By the end of the century, Arctic Sea ice may disappear, and ice-free regions in Antarctica could increase to 25 percent. Saikkonen warns that the melting of Antarctic glaciers could raise sea levels by five meters, affecting coastal ecosystems and human populations worldwide.
The researchers argue that biodiversity can recover after climate-related disturbances, but future ecosystems may consist of new species assemblages. They emphasize the importance of genetic diversity and species interactions to support future biodiversity and ecosystem functions.
"Thus, tackling climate change-driven biodiversity loss is important," Saikkonen stresses.
Related Links
University of Turku, Finland
Beyond the Ice Age
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