Résumé
Miscommunication may induce a high risk of unnecessary escalated fights
between competitors (populations to species), resulting in selection
favoring signal divergence through agonistic character displacement (ACD).
When signals allowing discrimination between competitors are also involved
in mate recognition, ACD could explain reproductive character displacement
(RCD). We tested interference competition between males as a potential
driver of RCD (here, subspecies recognition) in a secondary contact zone
between two mouse subspecies (Mus musculus musculus and Mus musculus
domesticus) displaying asymmetric dominance. Since such asymmetry could
create a conflict between subspecies (compatibility) and quality
(dominance) recognition in the contact zone, we tested for geographic
variation in female preference for dominant males in the subordinate
subspecies, musculus. We assessed competition between males and tested ACD
during dyadic encounters comparing behavior displayed during trials
between heterosubspecifics originating from populations close to the
secondary contact (“contact”) and further away (“allopatric”). We also
compared behavior of contact versus allopatric males during
homosubspecific versus heterosubspecific trials to test whether subspecies
discrimination evolved under competitive interference. Although domesticus
dominated most heterosubspecific trials regardless of geographic origin,
agonistic behavior was more marked (i.e., lower attack latencies) during
contact than allopatric encounters, suggesting that ACD occurred.
Comparing behavior during homosubspecific and heterosubspecific
encounters, only allopatric musculus displayed differences, that is,
higher attack latencies toward heterosubspecifics, indicating that
discrimination between competitors did not evolve with ACD. Finally,
although allopatric musculus females seemed to prefer dominant males,
their contact counterparts did not, suggesting that “compatibility” may
have outweighed “quality” under a risk of hybridization.