Correlated Changes in Body Melanisation and Mating Traits of Drosophila melanogaster: A Seasonal Analysis

Altitudinal localities of the northern India are associated with high seasonal changes. Drosophila melanogaster flies are darker during the winter season as compared to the autumn season. We tested the hypothesis whether there are altitudinal clines for mating related traits. We observed negative cline for mating latency and positive for copulation period along altitude in D. melanogaster. We further tested if seasonally varying body melanisation is correlated with mating propensity in D. melanogaster. Thus, we examined the D. melanogaster flies collected during autumn and winter season for changes in body melanisation and mating-related traits. Flies from the winter season show high melanisation, copulation duration and fecundity/day as compared to the autumn season flies. By contrast mating latency is longer during autumn as compared to winter season. Based on within- and between-population analysis, body melanisation shows positive correlation with copulation duration and fecundity/day, while negative correlation with mating latency. Within-population analyses show no correlation between body size and ovariole number with body melanisation. Thus, our data suggest that seasonal changes in body melanisation are correlated with mating latency, copulation duration and fecundity/day, but no correlation with body size and ovariole numbers. Further, we observed that seasonal changes in these clines, although have some component of plasticity, have strong genetic basis as the seasonal and population differences were maintained for various traits after 8 generations in the laboratory.