The unique light environment of Earth’s polar regions creates conditions that favor the formation of circumpolar hybrid zones around the North and South Poles, according to a new study. These extreme conditions synchronize the reproductive phenology of different species, forcing them to have a shorter breeding season, which could support biodiversity in the long term.

Aurora borealis affects biodiversity

In a recent research paper, Professor Kari Saikkonen from the University of Turku, Finland, and colleagues presented a new theory on how the auroral environment has affected biodiversity over millions of years. A study published in the journal One Worldinvestigates the role of unique light cycles near the poles in shaping long-term biodiversity.

Extreme aurora cycles

The daylight regime on Earth varies considerably with latitude. At the equator, day and night are roughly the same year-round, with only minor seasonal changes in day length as one moves away from the equator. However, closer to the poles, there is significant seasonality, resulting in phenomena such as the “midnight sun” in summer, when daylight lasts 24 hours, and the “polar night” in winter, when the sun does not rise for months. Arctic and Antarctic Circles.

“The basis of our theory is the hypothesis that over-illumination of the polar regions creates hybrid zones in both polar regions,” Saikkonen said.

Seasonal changes in day length

Unlike temperature, which can vary unpredictably with local and global climate, day length is a constant environmental factor that varies with latitude. Many organisms, especially photosynthetic ones such as plants and some microbes, have adapted to use seasonal changes in day length as cues to determine the timing of reproduction.

Because many organisms rely on light for signaling, the auroral environment increases the likelihood that closely related plant species will flower at the same time. This creates opportunities for hybridization, when organisms mate with individuals of another species or variety.

Aurora and hybridization

Saikkonen noted that although hybridization is common in almost all groups of organisms, its role in maintaining biodiversity is not fully understood.

“Hybridization can also involve backcrossing, where hybrid individuals mate with members of the original species. This allows genes to be transferred between species and create new adaptive gene combinations suited to different environmental conditions,” Saikkonen explained.

At lower latitudes, where day length varies little between seasons, the breeding times of different populations or subspecies are less likely to overlap, and therefore hybridization is less common. However, in polar regions, unique light cycles may encourage more frequent hybridization, leading to new biodiversity over long geological periods.

Evolution of biodiversity

“Latitudinal shifts in species diversity during cold and warm cycles on Earth cause periodic isolation and contact between species. This leads to species mixing and divergence, resulting in the emergence of new biodiversity over long periods of time,” Saikkonen said. Microbes have played a critical role in the evolution of biodiversity since the beginning of life, and they continue to have a significant impact on maintaining and enhancing global biodiversity.

“Microbes are ubiquitous and increasing evidence shows their high adaptive potential due to their short life cycle. Many microbes are light-sensitive and affect the health of almost all plants and animals. Since the microbiota of all plants and animals are different, they need to be considered as a whole,” said Saikkonen.

Polar regions are warming rapidly

Experts suggest that light-sensitive microbes may play a role in helping plants adapt to extreme light conditions in polar regions. Climate change and biodiversity loss are among the biggest global threats to ecosystems today. Polar regions in particular are warming much faster than the global average, 2 to 4 times faster.

“Climate models predict that Arctic sea ice will melt by the end of this century. During the same period, the ice-free area of ​​Antarctica will increase from today’s 2 percent to almost 25 percent,” he said.

“The melting of the West Antarctic ice sheets alone could cause sea levels to rise by five metres, threatening 10% of the world’s population and most of the world’s coastal ecosystems in the coming decades or centuries.”

Biodiversity loss due to climate

The researchers argue that the traditional species-based approach to biodiversity should be expanded to include the genetic diversity of organisms and the importance of microbial-associated plants and animals.

“We assume that in the long term, biodiversity can survive disturbances and mass extinctions, but ecosystems will restructure into new species clusters,” Saikkonen said.

“This requires greater attention to the importance of ensuring sufficient genetic diversity, species diversity and potential for species interactions to support future diversity and ecosystem functions and services. This is critical to combating biodiversity loss driven by climate change.”