Gender based disruptive selection maintains body size polymorphism in Drosophila melanogaster.
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Date
2014-09
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Abstract
Darwinian fitness in holometabolous insects like the fruit fly Drosophila melanogaster is reported to be positively
correlated with body size. If large individuals in a population have higher fitness, then one would expect directional
selection to operate leading to uniformly large individuals. However, size polymorphism persists in nature and needs
further probing. We assessed the effect of body size on some of the fitness and fitness-related traits in replicate
populations of genotypically large, genotypically small and phenotypically small D. melanogaster flies. In this study,
the time taken to attain reproductive maturity and copulation duration were independent of fly size. Fecundity and
longevity of large females were significantly higher when they partnered genotypically small males than when they
were with genotypically larger or phenotypically small males. The increased female longevity when in association
with genotypically small males was not due to selective early death of males that would release the female partner
from presumed cost of persistent courtship. On the contrary, the genotypically as well as phenotypically small males
had significantly higher longevity than large males. The virility of the genotypically small males was not significantly
different from that of genotypically large males. Our results clearly show that selection on body size operates in the
opposite direction (disruptive selection) for the two genders, thus explaining the persistence of size polymorphisms in
the holometabolous insect, Drosophila melanogaster.
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Keywords
Body size, disruptive selection, Drosophila, fitness
Citation
Handa Jaya, Chandrashekara K T, Kashyap Khushboo, Sageena Geetanjali, Shakarad Mallikarjun N. Gender based disruptive selection maintains body size polymorphism in Drosophila melanogaster. Journal of Biosciences. 2014 Sep; 39 (4): 609-620.