Climate change is predicted to promote species' range shifts and invasions from southern latitudes northwards. However, climate change does not affect the seasonal variation in day length. The length of the day in northern latitudes still depends on the position of Earth in relation to the Sun.
The photoperiodism of species -- in other words, their ability to adapt to seasonal variation in day length and quality of light -- plays an important role when species attempt to expand their distribution range northwards, note the expert group headed by professor Kari Saikkonen at MTT Agrifood Research Finland in their article published in the April edition of the journal Nature Climate Change.
"The models that predict species shifting do not, however, take the effects of photoperiodism into account at all. This is particularly the case with models which predict the effects of climate change on the spread of species," the authors state.
However, the authors write that adaptation to seasonal fluctuations in day length and amount and quality of light can be studied and the photoperiodism of species can be incorporated into existing models that predict the effects of climate change.
The European light climate will slow shifts across the Atlantic
Thanks to the effect of the Gulf Stream, Western Europe enjoys the same climate conditions as North America but at higher latitudes. At the same time, the day length and the quality of light in northern latitudes change radically from summer to winter.
Although Europe and North America are similar areas in terms of their biological and geographical features, the shift of species has been more common from Europe to North America than in the opposite direction.
The authors state that adaptation to seasonal fluctuations in day length and quality of light also plays an important role in changes in the distribution range of species. Therefore, adapting to a new light environment may be one key factor which could limit the spread of species from North America to Europe.
At temperate and cold latitudes, timing of reproduction is as essential for plants as the timing of dormancy, hibernation and migration is to many animals. The shorter the optimum growing period becomes as you move towards the poles, the more important it is to time growth and reproduction correctly.
The orbit, tilt and position of Earth determine the seasonal fluctuations in day length. The photoperiodic signals produced by these changes give plants and animals the cues according to which they coordinate their lifecycle events.
The ability to use photoperiodic cues is inherited
Because photoperiodic life-history traits are inherited, it is necessary to understand their genetic regulation to predict which species are likely to shift across latitudes.
However, very little is known about adaptation to seasonal changes in day length and quality of light. Thus it is unclear how photoperiodism limits the expansion of the distribution range of individual species across latitudes.
Photoperiodism may slow the shift of plants towards the poles. Local species may still retain their competitive position as they have precisely adapted to the local photoperiodic cues, which remain the same despite climate change.
A poleward shift in arable environments as a result of climate change offers opportunities for crop species and the use of crop-production technologies also at higher latitudes. A broader understanding of photoperiodism could also offer valuable viewpoints on plant breeding strategies.
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