We investigated geographical variations in thtee fitness-related traits(body melanisation,ovariole number and fecundity)in laboratory-reared offspring of 10 popula-tions of Drosophila melanogaster.The populations were collected from adjacent lowland and highiand localities (～80-100 km apart)in the tropical as well as subtropical regions (11.15-31.06°N)coveting alineardistance about 3 000kilometers from South to north on the Indian subcontinent.Persistence of within-as well as between-population differences at 21℃ suggest that observed variations in fimess-related traits have a genetic basis.Popula-tions from higher altitudes showed consistently higher trait values(1.4-fold increase)as compared with their corresponding lowland populations.By contrast,latitudinal variations were about two-fold higher across the entire continent.Along latitude as well as altitude,population means showed higher correlation values(r>0.98)between all the three fitness traits.However,on the basis of within-population analysis(assorted darker and lighter flies),changes in body melanisation were significantly correlated with fecundity but not with ovariole number.ThUS,analysis of within-population trait variability should be preferred as compared with data On population means for adaptive significance of fimess-related traits.In the present study,the role ofclimatic selection iS evident from regression analysis with changes in annual average temperature of the sites of origin of populations along latitude as well as altitude.