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Copyright 2008 by the Genetics Society of America DOI: 10.1534/genetics.107.086363

Summary: Copyright 2008 by the Genetics Society of America
DOI: 10.1534/genetics.107.086363
Variation and Evolution of Male Sex Combs in Drosophila: Nature of
Selection Response and Theories of Genetic Variation for Sexual Traits
Abha Ahuja and Rama S. Singh1
Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada
Manuscript received December 21, 2007
Accepted for publication February 18, 2008
We investigated the genetic architecture of variation in male sex comb bristle number, a rapidly evolving
secondary sexual character of Drosophila. Twenty-four generations of divergent artificial selection for sex
comb bristle number in a heterogeneous population of Drosophila melanogaster resulted in a significant
response that was more pronounced in the direction of low bristle numbers. We observed a strong positive
correlated response to selection in the corresponding female transverse bristle row. The correlated response
in male abdominal and sternopleural bristle numbers, on the other hand, did not follow the same pattern as
sex comb bristle number differences between selection lines. Relaxation-of-selection experiments along
with mate choice and fecundity assays using the selection lines developed demonstrated the action of sta-
bilizing selection on sex comb bristle number. Our results show (1) substantial genetic variation underlying
sex comb bristle number variation; (2) a weak relationship between the sex comb and developmentally
related, non-sex bristle systems; and (3) that sexual selection may be a driving force in sex comb evolution,


Source: Alwes, Frederike - Department of Organismic and Evolutionary Biology, Harvard University


Collections: Biology and Medicine