Population genetics of inversion polymorphism in Drosophila ananassae

Area of Science:

• * Population genetics
• * Evolutionary biology
• * Drosophila genetics

Background:

• * Drosophila ananassae is a cosmopolitan species with a circumtropical distribution.
• * This species is notable for spontaneous male recombination and is common in India.
• * Previous studies have focused on inversion polymorphism in Indian D. ananassae populations.

Purpose of the Study:

• * To investigate the population genetics of inversion polymorphism in Indian Drosophila ananassae.
• * To analyze the genetic divergence, heterosis, and chromosomal associations related to inversions.
• * To explore the behavioral basis of inversion polymorphism, specifically mating ability.

Main Methods:

• * Analysis of inversion frequencies (AL, DE, ET) in 29 natural populations.
• * Quantitative assessment of genetic divergence and heterosis.
• * Examination of intra- and interchromosomal associations and linkage disequilibria.
• * Testing mating ability of different karyotypes in relation to inversion frequencies.

Main Results:

• * Three cosmopolitan inversions (AL, DE, ET) are widespread in Indian populations.
• * Significant genetic divergence in inversion polymorphism was observed, with southern Indian populations showing more differentiation.
• * Heterosis was detected for these inversions, but without evidence of coadaptation; mating activity was higher for common inversions and heterokaryotypes.

Conclusions:

• * Inversion polymorphism in Drosophila ananassae shows considerable geographic variation and genetic divergence.
• * Heterosis associated with inversions appears to be simple luxuriance, not populational coadaptation.
• * Behavioral traits, such as mating propensity, may play a role in maintaining inversion polymorphism.