Abstract: Female preference for male ornament is favored by sexual selection. It is not clear whether the preference is limited to male ornament only or actually for genes that affect fitness of the progeny. In Drosophila biarmipes, females prefer to mate with males that are able to provide greater physiological tolerance to climatic stresses, i. e., males provide direct benefit of fitness to the females or their offsprings. Laboratory studies in D. biarmipes have evidenced the role of wing spot during courtship but its ecological significance remains unclear. We tested the hypothesis whether spotted and spotless males and progeny from sexually preferred males of D. biarmipes vary in their levels of environmental stress tolerances. Our results showed that the male flies with spotted wings performed significantly better in their mating success under desiccation or cold stress than the males with spotless wings. In contrast, spotless males mated more frequently under highly humid conditions. We also found significantly higher fecundity of females mated with the males with spotted wings under drier condition and higher egg-to-adult viability of the resulting progeny. Our results are consistent with good gene sexual selection hypothesis, suggesting that mate choice could provide indirect benefits to females. This is the first report on the ecological significance of wing color dimorphism in a tropical species-D. biarmipes.

Key words: Drosophila biarmipes, wing spot, dimorphism, sexual selection, good genes, mating, preference