Inversion polymorphisms in Japanese natural populations of Drosophila melanogaster.

Abstract

Four common cosmopolitan inversions (2Lt, 2RNS, 3LP, 3RP), 4 rare cosmopolitan inversions (2LA, 3LM, 3RC, 3RMo) and 2 recurrent endemic inversions (2LW, 3LY) were distributed in Japanese natural populations of D. melanogaster. Unique endemic inversions [17] were randomly detected in many natural populations and in stocks that originated from a small number of wild caught flies. The frequency of inversions was generally higher in Southern populations than in Northern populations, especially in the case of In(3R)P. The polymorphic inversions did not show any heterosis. The frequencies of inversion heterozygotes were almost equal to the expectations, with a few exceptions of a scarcity of the heterozygotes over the expectation. In the Katsunuma population, some inversions decreased remarkably within 10 yr, which resulted in the change of abundance order among 4 common cosmopolitan inversions. This kind of change might have occurred in the Shiojiri population. Both populations are very interesting in that new inversions are increasing in frequency and replacing the old ones.