Seasonal changes of chromosomal inversion polymorphism in a Drosophila subobscura natural population from southeastern European continental refugium of the last glaciation period.

Chromosomal inversion polymorphism was studied in a natural population of Drosophila subobscura from Djerdap gorge of Danube river, that represents one of southeastern European continental refugiums during last glaciation period. The existence for changes of chromosomal inversion polymorphism during different periods of time was tested. Observed very high abundance of chromosomal arrangements and lower IFR value grouped this population to central European populations. It was characterized with O7 and O(3+4+5) arrangements, not found in other populations from the region analyzed. Except in this population from warmer habitat, observed E(1+2+9+12) chromosomal arrangement was found, in the region analyzed, only in one population from Mediterranean refugial area. Many similarities have been observed between population from Djerdap gorge and other populations from the region analyzed, indicating that process of post-glacial migration may have started from this southeastern European refugium area. Seasonal changes in the frequencies for Est and O(3+4+7) chromosomal arrangements where Est was more frequent during the spring period and O(3+4+7) during the summer period were found. The changes for J-chromosome (Jst/Jst), E-chromosome (Est/E(1+2+9); E(8)/E(1+2+9) and O-chromosome (Ost/O(3+4+22); O(3+4)/O(3+4); O(3+4+1)/O(3+4+7) whose karyotypic combination frequencies were associated with seasonal changes were also found. These changes most probably represent associations with seasonal climatic changes in the population analyzed, supporting adaptivity of chromosomal inversions in D. subobscura.