Does evolution reduce the body size? A study of the four members of newly evolved nasuta-albomicans complex of Drosophila.

Our long range interracial hybridization experiments between a pair of cross fertile races, Drosophila nasuta (2n = 8) and D. albomicans (2n = 6) have resulted in the evolution of two new karyotypic strains under laboratory conditions, which are named as Cytorace 1 and Cytorace 2. These Cytoraces harbor chromosomes from both parents. Here, we compare the body size of the parental races and newly evolved Cytoraces and the relationship between the body size and fitness. Analysis reveals that the parental races have reduced fertility and are larger in body size than newly evolved Cytoraces. Thus, the newly evolved Cytoraces show reduced body size and better fitness in the course of their evolution.