Inheritance of courtship song variation among geographically isolated populations of Drosophila mojavensis

Courtship song variation in many Drosophila species evolves rapidly and is thought to contribute to species-specific mate recognition. Studies using song playback experiments have shown that courtship songs are part of this recognition system in the sibling species D. mojavensis and D. arizonae. We examined variation in components of courtship songs in D. mojavensis to evaluate further the influence of courtship song divergence on sexual isolation. We found significant geographical variation in mean interpulse interval and mean burst duration, and significant variation in mean burst duration among geographically isolated populations from Baja California and mainland Mexico and Arizona. Significant regional differences in these song components were detected, as well as variation among populations nested within regions. Residual maximum likelihood (REML) analysis of F1 and F2 generations from a cross between a Baja California and an Arizona population revealed additive autosomal influences on mean interpulse interval with a significant effect of dominance and significant effects of the Y chromosome on mean burst duration. Regional differences in song variation and the type of genetic architecture observed are consistent with patterns of geographical variation associated with the colonization of the mainland from Baja California and documented differences in sexual isolation between populations.