Vol. 50 No. 5, 2011

Evidence for Incipient Sexual Isolation within Drosophila ananassae

Punita Nanda and Bashisth Narayan Singh*

Genetics Laboratory, Department of Zoology, Banaras Hindu Univ., Varanasi 221005, India

Punita Nanda and Bashisth Narayan Singh (2011) Intraspecific sexual isolation was studied by employing 20 mass culture laboratory stocks of Drosophila ananassae established from naturally impregnated females collected from different localities in India using a male-choice technique. In total, 190 crosses involving 20 strains were carried out in which each strain was reciprocally tested with other strains. The results showed that in 54 of 190 crosses, there was a preference for homogamic matings, and differences between homogamic and heterogamic matings were statistically significant in one of the reciprocal crosses; this provides evidence for asymmetry in sexual isolation, while three of 190 crosses showed symmetrical sexual isolation in which positive assortative mating was observed in both reciprocal crosses. In 133 of 190 crosses, there was no sexual isolation. These findings provide evidence for instability of mate recognition leading to behavioral isolation within D. ananassae. These results are discussed in light of results reported in other species of Drosophila.

Key words: Drosophila ananassae, Genetic divergence, Models of asymmetry, Natural populations, Sexual isolation.

*Correspondence: E-mail:bashisthsingh2004@rediffmail.com, bnsingh@bhu.ac.in