Monitoring chromosomal polymorphism in <em>Drosophila subobscura</em> over forty years

Abstract

The inversion chromosomal polymorphism of Drosophila subobscura is considered to be adaptive as a result of its responses at different time scales to temperature changes. This work reports the longest-term study of chromosomal polymorphism for a single population of D. subobscura with climatic data from the collecting site itself. The chromosomal analysis of D. subobscura samples collected six times over a 40-year period at the same location and in the same seasonal interval has revealed the continuous presence of 16 common and six moderately rare chromosomal arrangements through the period. This analysis also corroborates the previously detected negative relationship between the frequencies of the standard (cold-climate) arrangement on each of its five chromosomes and temperature, as well as between a comprehensive measure of cold adaptation (the total autosomal proportion of standard arrangement) and temperature. These and previous results would support that species harboring cold- and warm-adapted polymorphic chromosomal arrangements, like D. subobscura, can rapidly respond to environmental changes.