Global warming and chromosomal inversion adaptation in isolated islands: Drosophila subobscura populations from Madeira

Abstract

Global warming is an environmental phenomenon to which species must adapt to survive. The chromosomal inversion polymorphism of Drosophila subobscura constitutes a genomic architecture that provides an adaptive capacity to this species. Until now, their populations studied were continental or in islands located near the coastline. In these conditions, gene flow could be a relevant mechanism allowing the movement of thermally adapted inversions between populations. For this reason, we obtained and compared the D. subobscura inversion polymorphism from Madeira, an Atlantic isolated island, with those reported there thirty eight and forty six years ago. Moreover, we studied whether global warming affected this island by measuring mean, maximum and minimum temperatures in a fifty-five years period. We detected significant increase of all these atmospheric parameters in agreement with climate change expectations. Focusing in thermal adapted inversions, their frequencies and the CTI (Chromosomal Thermal Index) values remained rather stable over years. Furthermore, J, U and O chromosomes almost present fixation for 'warm' adapted inversions. Thus, island populations of D. subobscura might be in the threshold of being endangered. However, apart from selection other evolutionary mechanism such as phenotypic plasticity or thermoregulatory behavior could be involved in the survival of the species populations. Finally, being a generalist species living in humanized environments could also favor the persistence of their Madeira populations.