Evolutionary rate of adaptive chromosomal inversions in Drosophila subobscura (Diptera: Drosophilidae) in response to global warming

In the face of global warming, insects can employ various survival strategies. One possibility is that natural selection favors genetic combinations that are adaptive to this environmental situation. In some species, chromosomal inversions allow a particular combination of genes to be transmitted intact across generations, provided it is adaptive. Drosophila subobscura could therefore be considered a model species, given its rich chromosomal inversion polymorphism and its relationship with climate change. This polymorphism was studied in the Djerdap (Serbia) population in 2024, and its composition was found to have changed over time when the results were compared with those from 2001 and 2002. A significant decrease in 'cold' and an increase in 'warm' adapted inversions were observed when comparing 2001 and 2024. Also, the CTI (chromosomal thermal index) value for the whole karyotype in 2001 (0.162) was significantly different to that in 2024 (0.332) (adjusted p = 0.0084). Of the inversions studied, nine presented an observed frequency outside the interval expected assuming genetic drift. However, a change in agreement with global warming was detected in only five of these inversions, while the frequency of two 'non-thermal' adapted inversions also increased. Finally, an evolutionary rate was calculated by dividing the difference in frequency between 2024 and 2001 by the number of years that had elapsed. The values obtained for the 'cold', 'warm' and 'non-thermal' adapted were -0.0030126, 0.0030148 and -2.609 10-6, respectively. These values are lower than those previously reported for the Apatin (Serbia) population.