Cosmopolitan Inversions in a Cosmopolitan Species of Drosophila Commonly found in India

Structural and numerical aberrations are known to occur in different species of plants and animals including humans. Paracentic inversions in Drosophila, pericentric inversions in grasshoppers, trananslocations in Oenothera lamarckiana and polyploidy in plants have been studied in detail. The genus Drosophila is an interesting biological model which belongs to the family Drosophilidae (Class-Insecta and OrderDiptera) characterised by rich species diversity at global level and also in India. More than 1500 species have been rereported at global levl and about 150 species from India. Inversions were detected about hundred years ago in Drosophila melanogaster through their suppressive effects on recombination by Sturtevant. Inversion polymorphism caused due to paracentic inversions have been studied in a lage number of species and about 100 species have been found to be chromosomally polymorphic. There are a large number of species which remain chromosomally monomorphic. Inversions polymorphism has been studied in detail in certain species with respect to the patterns, degrees and population dynamics of inversion polymorphis. In this article, briefly the patterns and population dynamics of inversion polymorphism have been described in Drosophila ananassae, a cosmopolitan and domestic species, commomly found in India and characterized by a number unusual genetic features. Although it contains a large number of paracentric inversions in its natural populations, three cosmopolitan inversions having monophyletic origin are distributed at global level.