Genetic variability assessed by competitive ability and ISSR markers in the members of the Nasuta-albomicans Complex of Drosophila

Abstract

The Nasuta-albomicans Complex (NAC) of Drosophila is an assemblage comprising of two morphologically indistinguishable members of the nasuta subgroup of the immigrans species group namely, Drosophila nasuta nasuta, Drosophila nasuta albomicans and 16 cytoraces, which have been evolved through a long range hybridization between D. n. nasuta and D. n. albomicans. This complex is an artificial hybrid zone of Drosophila with “allo-sympatric” populations, which exhibits differences in their cytogenetic differentiation, incipient sexual isolation, body size and fitness. The objectives of our study were to (a) assess the competitive ability of four laboratory evolved races - cytorace 1, cytorace 2, cytorace 3, cytorace 4 along with their parents, D. n .nasuta and D. n. albomicans (b) examine the DNA polymorphism among these hybrid races and their respective parents based on ISSR markers and (c) bring out the correlation, if any, between the above two. Among the six races, overall competitive ability was higher in D. n. nasuta, D. n. albomicans and cytorace 1 than other races. Cytorace 1, cytorace 2 and cytorace 4 are with 20-23 % of DNA polymorphism while cytorace 3 is with 10.7% of DNA polymorphism with reference to four ISSR profiles. Thus, one can surmise that cytorace 1, cytorace 2 and cytorace 4 with increased genetic variability exhibited better fitness while cytorace 3 with the least DNA polymorphism showed reduced competitive ability.