Researchers in Finland suggest that the distinctive light conditions of the Earth’s polar regions lead to the formation of unique hybrid zones around the North and South Poles. These extreme environments promote synchronized reproductive timing among various species, forcing all species into a limited period for reproduction. This synchrony is crucial for maintaining biodiversity over time.
Researchers in Finland suggest that the distinctive light conditions of the Earth’s polar regions lead to the formation of unique hybrid zones around the North and South Poles. These extreme environments promote synchronized reproductive timing among various species, forcing all species into a limited period for reproduction. This synchrony is crucial for maintaining biodiversity over time.
In a recent study published, Kari Saikkonen, a Professor of Subarctic Ecology at the University of Turku, Finland, along with his research team, introduced a novel theory regarding how the polar light environment supports biodiversity over geological timescales that span millions of years. The duration of daylight and nighttime varies across the globe, characterized by equal light and dark cycles at the Equator, gradual seasonal changes moving away from it, and significant seasonal variations near the Poles. In the extreme North and South, within the Arctic and Antarctic circles, phenomena like the “midnight sun,” where sunlight lasts 24 hours during summer, and the “Polar Night,” where the sun doesn’t rise for several months in winter, occur.
“The core of our theory suggests that the extreme light conditions in the polar areas create hybrid zones in both polar regions,” states Saikkonen.
In contrast to temperature, day length is a consistent environmental factor that reliably alters with latitude without being influenced by local or global climate variations. As a result, many organisms, particularly photosynthetic organisms like plants and various microbes, have evolved to use changes in day length each season to time their reproductive cycles. The light serves as a critical signal, which increases the chance that related plant species will flower simultaneously, ultimately fostering hybridization opportunities.
Hybridization occurs when organisms breed with different species or varieties. This can happen intentionally, as seen in many agricultural practices aimed at cultivating specific traits, or naturally when species cohabitate and share compatible biology.
“While hybridization is prevalent across nearly all organism groups, its contribution to sustaining biodiversity has not been fully recognized. Hybridization can also lead to backcrossing, where hybrids mate with individuals from the original species, facilitating gene transfer between species and creating novel gene combinations that can help them adapt to changing environmental conditions,” Saikkonen explains.
In areas with lower latitudes, slight variations in day length from season to season typically do not overlap with the reproductive timings of genetically distinct populations, subspecies, or varieties within a species complex, thus limiting hybridization.
“Consequently, the shifts in species ranges across latitudes during the cycles of cooler and warmer climatic periods lead to repeated isolation and interaction among species. This interaction drives mixing and differentiation, resulting in new biodiversity over extensive geological timescales,” adds Saikkonen.
Microbes are crucial for the development and maintenance of biodiversity
Microbes have been integral to the evolution of current biodiversity since the dawn of life and continue to play a vital part in preserving and enhancing global biodiversity.
“Microbes are everywhere, and ongoing research indicates that they possess a considerable adaptive capacity due to their short life cycles. Many microbes are sensitive to light and have an impact on the health of nearly all plants and animals. As all plants and animals carry diverse microbiota, they should be regarded as a collective unit,” Saikkonen observes.
In this study, Saikkonen and his team propose that photosensitive microbes could assist plants in adapting to the polar climate.
Climate change significantly affects Earth’s polar regions
Biodiversity loss and climate change represent some of the biggest threats to ecosystems and their services in human history. The polar regions of Earth are warming at an alarming rate—up to 2 to 4 times the global average.
“Climate models anticipate that Arctic sea ice may disappear by the end of this century. In the same period, the ice-free area in Antarctica could rise from about 2 percent today to nearly 25 percent. The melting of just the western Antarctic glaciers would elevate sea levels by five meters, endangering 10 percent of the global population and numerous coastal marine ecosystems in the coming decades or centuries,” warns Saikkonen.
The researchers challenge the traditional focus on species in discussions about biodiversity by emphasizing the importance of not only species but also the genetic diversity of organisms and the crucial role of microbes associated with plants and animals.
“We suggest that biodiversity can, in the long run, recover after disturbances and mass extinctions, although ecosystems will undergo restructuring with new species combinations. This underscores the urgent need to ensure adequate genetic, species, and interaction potentials to support future diversification and ecosystem functions and services.
Thus, addressing climate change-induced biodiversity loss is of utmost importance,” emphasizes Saikkonen.
