The Role of Intermale Aggression in Speciation Processes in Chromosomal Races of House Mice

Aggressive behaviour in house mice is commonly considered an adaptive trait 1 expressed mainly within species to modulate social structure and population dynamics by spacing out individuals. Such behaviour may, however, also play a major role favouring competitive exclusion between contiguous evolving populations and thus help preserve population identity 2 . This latter process may be crucial during speciation when reproductive isolation between diverging populations is incomplete. For example, it has been suggested that inter-specific aggression maintains parapatric distribution between four chromosomal races of the Molerat Spalax ehrenbergi in Israel (the ranges of the races meet but do not overlap) and contributes to the eventual establishment of reproductive isolation 2–3 .