Photo: Pete Linforth

Evolutionary response to climate change accelerated in the past 20 years. But, as Spanish scientists claim, the fact may help in adaptation to ongoing transformation.

Global warming becomes a new reality which impacts life on Earth. Now no one is questioning the ecological changes it brings and more and more often they are scaring. They are even called irreversible in the newly published in Springer Nature paper led by Fransisco Rodriguez-Treiles from University of Barcelona UAB. Many scientists pursue catastrophic visions along with the collapse of human civilization as such. But the study conducted on population of European fruit fly – Drosophila subobscura and its capacity to adapt to new conditions is optimistic. Evolution provides solutions beneficial for biological organisms what may allow all of us to survive. So what about the solutions?

In accordance with the study on fruit flies that suffer the most from global warming and are the cutest organisms to study, the answer is genetic variation. What is that? This is an existing in DNA section of genes with certain, lets say, properties. Spanish scientists foresee the tolerance for higher temperatures in the case of European flies will take place by 2050. Central European form is to be replaced by Mediterranean form that obtained boosted tolerance for heat. And what is more the forecast has been done based on detailed examination of flies’ DNA which, in response to heat is triggering an old evolutionary mechanism of genetic variation that digs out chromosomal composition capable to cope with climate change.

Biological response to warming

Who is the looser? – someone may ask as in evolution it is easier to lose than to gain. Small populations with low genetic diversity i.e. these ones which are closed for genes inflows. But, as it has been stated in the study, the capacity to cope with global warming in the case of European fruit fly is to not be determined by novel genetic inversions. Evolution by mixing genes of various populations will just reward these sections of DNA compositions capable to survive in new environment. At the same time lines more homogeneous are to vanish. And this is the loss in the evolutionary shift towards boosted tolerance for heat.

How is this possible? Very simple. DNA of each living organism is built from more or less the same biological material. Specified sections of DNA and chromosomes which determine our look and basic attitudes in our behavior repeat in the whole code. Scientists checked out sections putatively adapted to warming. They found that frequencies of low latitude inversions increased with the magnitude of global warming between the sample periods. So novel patterns of flies’ genes are emerging due to climate change caused by humans.

What is more? Taking into account previous studies on European fly from France, Spain, Netherlands, Germany and Austria the lines of flies split into south and north regions. And having in mind studies conducted over a half century ago, the change in frequencies of DNA sections capable to adapt to heat accelerated. In late 60-ties they occurred average in every 30 years while now every 20 years.

New phenotype expression?

Scientists analyzed five chromosomes in collected 12 samples. Chromosomes are this part of DNA which is transmitting genetic information. Each chromosome comprises one nucleotide of DNA what is sugar, phosphate group molecule and one of four nitrate alkali. The way the information is being passed is crucial for condition of live organism and thus to its health and lifespan. A total of around 7 thousand chromosomes were scored for gene arrangements for the study purpose. The arrangements depend on genetic information transmission and thus work of chromosomes. And they are the key for functionality of each DNA. No newly discovered, previously unreported inversions were detected. At the same time higher temperature in living area of studied flies’ samples increased of warm-latitude of chromosome arrangements.

The observed geographic heterogeneity in the timing of the genetic shift suggests that it is due in part to local adaptation rather than just to genetic drift or a northern migration of individuals from equatorial locations.

says Fransisco Rodriguez-Treiles from University of Barcelona UAB.

Genetic drift that is a fluctuation of a given gene variant which does not depends on mutation, migration or natural selection. Instead it comes from the population size what means the smaller group is more effective in eliminating certain allele (alternative form of a gene) or the specific allele becomes dominant among it. Spanish scientists explain that this is not the case on the way of European fruit fly adaptation to new conditions due to the large scale of the studied phenomenon – multiple populations shifting in the same direction across a wide geographic range – underlines Fransisco Rodriguez-Treiles. If, he adds, migration was responsible for adaptive to heat gene variants shift, frequencies of some sporadic inversions that are relatively common in North Africa should have also increased in Southern Europe, but this was not observed. What’s more, local adaptive variants are not homogeneous what stipulates that all five studied chromosomes of flies despite they started from similar levels of latitude differentiation individually contributed to the climate-driving shift. This suggests that the chromosomes differ in their effects on the thermal phenotype.

Central European fly is changing the most and the fastest as the observed shifts were twice as high in relation to the southern part of the region. In line with expectations and findings, heatwave caused a surge in the frequency o the more tolerant genotypes in D. subobscura. -Therefore, the acceleration in the European fly rate of evolutionary response observed in the present study is probably driven not only by the gradual increase in average temperatures, but also by more-frequent and longer-duration heatwaves – conclude scientists. They add the fact indicates fly may have the potential to adapt to higher temperatures. In general, the study results suggest that species with broad geographic ranges, large population sizes and high genetic diversity may have the evolutionary potential to cope with climate change.