Looking Under the Lamp Post: Neither fruitless nor doublesex Has Evolved to Generate Divergent Male Courtship in Drosophila

• Innate male courtship behavior evolves rapidly in Drosophila species
• fruitless and doublesex are known to control male courtship in Drosophila
• Cross-species transgenics test fruitless and doublesex for a role in behavior evolution
• fruitless and doublesex are not involved in courtship behavior evolution

SummaryHow do evolved genetic changes alter the nervous system to produce different patterns of behavior? We address this question using Drosophila male courtship behavior, which is innate, stereotyped, and evolves rapidly between species. D. melanogaster male courtship requires the male-specific isoforms of two transcription factors, fruitless and doublesex. These genes underlie genetic switches between female and male behaviors, making them excellent candidate genes for courtship behavior evolution. We tested their role in courtship evolution by transferring the entire locus for each gene from divergent species to D. melanogaster. We found that despite differences in Fru+ and Dsx+ cell numbers in wild-type species, cross-species transgenes rescued D. melanogaster courtship behavior and no species-specific behaviors were conferred. Therefore, fru and dsx are not a significant source of evolutionary variation in courtship behavior.

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