Inversion polymorphism in populations of Drosophila sulphurigaster albostrigata and Drosophila nasuta albomicans from Phuket, Thailand

Abstract

Two species of the Drosophila nasuta subgroup of the Drosophila immigrans group, D. sulphurigaster albostrigata and D. nasuta albomicans were investigated in this study. Collections of both species were made from Phuket, Thailand. Both species have similar salivary chromosomes, with four autosomal arms and one sex chromosome arm, and both are highly polymorphic for paracentric inversions. D.s. albostrigata accounted for the majority of the isolines collected and exhibited the greater number of inversions. One inversion, C14 was common to both species, indicating common ancestry. A non-random distribution of inversions was observed on the proximal end of chromosome III in both D.s. albostrigata and D. n. albomicans. An inter-collection comparison revealed that both rigid and flexible chromosomal polymorphism were operating in the two species, with a seasonal variation noted for one inversion in D. s. albostrigata. A non-random association of two inversions was observed in D. n. albomicans. Based on a comparison of the indices of crossing over, both D. s. albostrigata and D. n. albomicans were found to be more heterozygous than in previous studies, with D. n. albomicans appearing to have evolved further than D. s. albostrigata.

Molecular characterization of inversion breakpoints in theDrosophila nasutaspecies group

“…In D. albomicans , chromosome 3 fused to both the X and the Y chromosome, forming a neo-sex chromosome. Inversion polymorphism of the nasuta species group has been studied using cytogenetic techniques (Casu 1990; Lambert 1982;Pope 1987), and species in this group were found to be highly polymorphic for chromosomal inversions. However, no systematic characterization of inversions at the molecular level exists.…”