Inbreeding tolerance in two isolated populations of Harting's vole Microtus hartingi (Rodentia, Arvicolinae).

The adaptive effects of inbreeding are understudied, but accumulating evidence suggests that it plays a major adaptive role in speciation, as populations with a history of inbreeding are more prone to it. Differences in inbreeding tolerance in two populations of Microtus hartingi voles were studied through a series of experiments on reproductive behaviour and partner choice. Modelling an artificial polygyny via the formation of trios composed of a brother, sister, and an unrelated female has shown an uneven attitude towards inbreeding, which was closely linked to the reproduction strategy: voles of the Rhodopean population (RP) would reproduce communally with only a moderate decrease in reproduction success, while in monogamous M. hartingi ankaraensis voles from Central Anatolia (CAP), the reproductive success dropped almost to zero due to severe social stress resulting in heavily antagonistic behaviour between females; aggression levels rose with maturation. Studies of reproduction in pairs of relatives revealed the absence of inbreeding avoidance in the polygynous population (RP) and a sharp decrease in reproduction probability in the monogamous subspecies (CAP). Olfactory three-choice behavioural tests have proven that voles do not choose the smell randomly, juveniles do not have partner preferences, and adults choose the unrelated individual's odour. RP voles prefer to mate with kin first, whereas CAP voles mate with non-kin first. The differences in reproductive strategy might have evolved due to habitat fragmentation and restriction of natal dispersal in the RP which has been isolated from the ancient Anatolian Microtus hartingi population since the Pleistocene. The adaptation to communal reproduction via kin selection resulted in increased inbreeding tolerance. [ABSTRACT FROM AUTHOR]