ABSTRACT
Fissioncytorace-1, a member of the nasuta-albomicans complex of Drosophila is an evolutionary product of centric fission, which had occurred in the chromosome X3 of Cytorace 1, a hydridization product of Drosophila nasuta nasuta male (2n=8) and Drosophila nasuta albomicans female (2n=6). Cytorace 1 (males 2n=7; females 2n=6) has inherited this chromosome from its D. n. albomicans parent. The chromosome X3 of D. n. albomicans is a derivative of a centric fusion between the acrocentric chromosome 3 and the chromosome X of D. n. nasuta. The Fissioncytorace-1 has crossed 200 generations from the time of its evolution in the laboratory environment. When this centromeric fission race was subjected to some of the morphophenotypic and fitness assessment to find its overall population fitness showed, increased body size, sternopleural bristle, ovarioles, lifetime fecundity and fertility with reduced interspecific competitive ability and hatching success when compared with its parent (Cytorace 1). These results suggest that the hybrid races must have encountered an early event of recombinational raciation during their evolution in the laboratory environment, which is a unique observation in animal system illustrating the increase in the tempo of evolution after the event of hybridization.