Fitness consequences of body melanization in Drosophila immigrans from montane habitats
2009
SINGH, Shama | RAMNIWAS, Seema | PARKASH, Ravi
We investigated eight populations of Drosophila immigrans from low to high montane localities (600-2202 m) for altitudinal variations in abdominal melanization and fitness-related traits (desiccation resistance, copulation duration, and fecundity). On the basis of common garden experiments, persistence between-population differences at 21°C suggests that observed variations in fitness-related traits have a genetic basis. Parent-offspring regression analyses showed higher heritability (h²= 0.77) for melanization patterns on all the abdominal tergites. All the traits showed significantly higher repeatability across generations. Under colder and drier environments in dispersed montane localities, abdominal melanization and desiccation resistance significantly increased (1.5-1.9 fold) along altitude. Thus, there are correlated effects of abdominal melanization on desiccation resistance. Genetic correlations, based on family means, were significantly high between abdominal melanization and other fitness traits. Furthermore, darker flies along increasing altitude resulted in a 35-40% increase in copulation duration as well as fecundity. There are significantly positive correlations of abdominal melanization with copulation duration as well as fecundity on the basis of within- as well as between-population variations. Such observations are in agreement with the thermal budget hypothesis. Present data suggest that changes in body melanization impact fitness-related traits in montane populations of Drosophila immigrans.
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