Genetic variation for tolerance to high temperatures and its possible role in climatic adaptation in Drosophila melanogaster

SCHILMAN, P.E.; ROLANDI, C.; MENSCH, J; LIGHTON, J.R.B.

Workshop; 3° Workshop Ecofisiología: Interacciones de los organismos y su ambiente; 2017

The range of thermal tolerance is one of the main factors influencing geographic distribution of the species. Climate change projections predict increases in average and extreme temperatures over the coming decades, hence the ability of living beings to resist these changes will depend on physiological and adaptive responses. Short term responses may involve plastic modifications in the range of thermo-tolerance. On a longer time scale evolutionary changes will occur onthe basis of individual inheritable differences of this type of response. In this work, we will identify the genetic basis of tolerance to high temperatures in the fly Drosophila melanogaster and if this species presents genetic variability that allows expansion of its upper thermo-tolerance limit through processes of climatic adaptation. To do so, we used adult flies derived from a natural population belonging to the Drosophila Genetic Reference Panel for which their genomes have been sequenced. We characterized the phenotypic variation of the upper thermal limit in 37 lines by measuring knock down temperature (i.e., critical thermal maximum (CTmax)) by exposing flies to a ramp of increasing temperature (0.25° Cmin-1). 14% of the variation in CTmax is explained by the genetic variation across lines, without a significant sexual dimorphism. Through a genome-wide association study 14 regions of the genome associated to the CTmax were identified, corresponding mostly to regulatory regions. This suggests that their effect on CTmax could be mediated by changes in gene expression. In summary, this work shows that there is genetic variation for heat coma tolerance in this natural population and that several identified genes present alleles that would allow the expansion of the upper limit of thermo-tolerance through climatic adaptation processes.