Title: Comparisons of the inversion polymorphism in three Danish populations of the midge Chironomus plumosus L. (Diptera: Chironomidae)
Abstract: The chromosomal polymorphism in three Danish lake populations of the midge Chironomus plumosus L. was followed during a period of nearly three years. The populations exhibited differences in the composition of the chromosomal polymorphism and in the level of heterozygosity (= number of inversion heterozygotes per individual). The frequencies of larvae with a certain paracentric inversion located in the largest of the chromosomes showed remarkable differences between the three populations. In one of the lakes, in addition to a large frequency of larvae with this inversion, specimens heterozygous for the inversion were in great excess compared to the Hardy-Weinberg distribution. The frequency of the heterozygote varied during the year. The adjustments of the chromosomal polymorphism to the environments are discussed.