Abstracts (first author)
Local adaptation drives latitudinal frequency clines for chromosomal inversions in Drosophila subobscura
Climate change is already impacting the distribution and behavior of many species. Nonetheless, population genetic changes in response to global warming have been observed only for a few species. This is the case of Drosophila subobscura, a native Palearctic species that harbors a rich chromosomal inversion polymorphism with “warm climate” inversions increasing in frequency worldwide. However, the selective process that maintains inversions in populations is not clear yet. The two main hypotheses differ in how the genetic content of inversions varies along a geographical gradient; the local adaptation hypothesis states that an inversion will have the same genetic content in all populations, while the coadaptation model suggests that in each population the genetic content will be different. In order to elucidate which model is more suitable for D. subobscura, we have analyzed ten genes -six of them are candidates for thermal adaptation- located on the longest and inversion richest chromosome O of the species. The most frequent chromosome arrangements in two Spanish populations along a latitudinal gradient were analyzed. No within-inversion genetic differences were detected among populations, which suggest that the gene content along the gradient is rather constant for the various gene arrangements. Although gene flux between different inversions (either by gene conversion or double crossover) was detected, significant genetic differentiation among inversions for all genes mapped within the inverted fragments of the chromosome was found.