Divergence of odorant signals within and between the two European subspecies of the house mouse

The olfactory acuity of mice allows them to discriminate odors of conspecifics differing by a few genes. This acuity is used in habituation procedures where investigation of novel odors by the mouse can be translated into relative difference or similarity between the stimuli. This study adapts these behavioral procedures to address suprapopulation divergence among urinary odors in the house mouse. Specifically, we investigate geographical patterns of odor divergence within and between 2 subspecies of the house mouse, Mus musculus musculus and Mus musculus domesticus, which diverged in allopatry and met secondarily in Europe where they hybridize. Based on M. m. musculus perception, our study suggests that odors of the 2 subspecies differ in both allopatric and contact zone populations and that divergence is more marked in the latter. Our earlier studies documented mate preference and signal divergence between the 2 subspecies. Hence, we consider the role of the urinary odors as mating signals. We discuss how signal divergence between the 2 subspecies may relate to reproductive character displacement. This study validates the use of habituation procedures to reconstruct geographical patterns of odorant signal divergence, providing a strong methodological platform to address reproductive character displacement affecting cryptic mating signals in mammals.