Melanization plasticity of Drosophila kikkawai, Drosophila leontia and reciprocal hybrids under different temperatures

Abstract

• Drosophila kikkawai and Drosophila leontia produces hybrids. • No plasticity for melanization in D. kikkawai and D. leontia but hybrids show plasticity. • Generations proceed in the direction of female. Drosophila (Sophophora) kikkawai , Burla, 1954 and Drosophila (Sophophora) leontia , Tsacas & David 1978 are closely related sibling species, the former being cosmopolitan and the latter is restricted to tropical localities. We investigated the influence of introgressive hybridization on phenotypic diversity of the two sibling species in the present study. How hybridization supports the relative abundance of pure species according to latitudinal cline is the aim of this study because hybrids show a tendency to acquire geographical location of their parent species in equal or greater abundance. How hybridization supports the plasticity for melanization of hybrids is not explored yet. The two species can cross and generate hybrids. For this, we crossed true breeding strains of both species to obtain the hybrids i.e. dark female (♀) of D. kikkawai ( D. k ) with males (♂) of D. leontia ( D. l ) in cross I and light ♀ of D. k with ♂ of D. l in cross II along with their reciprocal crosses. Finally, we studied the plasticity of both species and their hybrids at 6 growth temperatures (14, 17, 21, 25, 28 and 31 °C). We found that there is no plasticity for melanization in true breeding darker and lighter strain of D. kikkawai as well as D. leontia whereas hybrids of both species showed high phenotypic plasticity. Significant differences in slope values across temperatures in parental and hybrid lines suggest plastic effects. Phenotypic variation in abdominal melanization in hybrids can be interpreted as a result of gene introgression with D. kikkawai . We conclude that introgressive hybridization might be an important, although underestimated, mechanism shaping species distribution and adaptation.