Centro de Biologia Ambiental / Departamento de Biologia Animal
Fac. Ciências Univ. Lisboa Campo Grande, Building C2, Floor 1
Abstracts (first author)
The fate of chromosomal inversion polymorphism during adaptation to a novel environmentPDF
Chromosomal inversions are widespread in Drosophila with strong evidence supporting an adaptive cause for the evolution and maintenance of inversion polymorphisms. One emblematic example of the adaptive role associated with inversions is the repeatable clinal variation in inversions frequencies in different continents as happens in Drosophila subobscura. More recently, it has been found that these inversion polymorphisms are shifting as a response to global warming. Both local adaptation and gene flow may be involved, the latter possibly overcoming historical constraints. Nevertheless, it is still unclear what forces are important in shaping the evolution of inversion polymorphisms. An approach to this issue is to study the evolutionary dynamics of chromosomal inversions of populations initially differentiated along a cline, during adaptation to a novel, common environment in the absence of gene flow. We use this strategy analyzing laboratory adaptation in Drosophila subobscura founded from contrasting European latitudes. Will natural selection in the new environment overcome the initial historical differences, promoting convergence of inversion frequencies? During the first 25 generations of adaptation to a common environment we found that the polymorphism of chromosomal inversions was gradually reduced in all populations. We also found persistent differentiation between populations from contrasting latitudes, though these differences reduced with increasing generations in the new environment. While genetic drift seems to play an important role in inversion frequency changes, we also found consistent increase in frequency of specific inversions (initially in low frequencies) across replicate populations, which suggests that selection also played a role. Altogether this study indicates that, in the absence of gene flow, inversion polymorphism evolves under a balance of selection and genetic drift with historical constraints also playing an important role.