1. ¹Department of Genetic Recombination and Segregation, Institute of Cytology and Genetics, Siberian Department of Russian Academy of Science, Novosibirsk, Russia
2. ²Department of Cytology and Genetics, Novosibirsk State University, Novosibirsk, Russia
3. ³Department of Comparative Animal Genetics, Institute of General Genetics, Russian Academy of Science, Moscow, Russia

Correspondence: Professor TI Axenovich, Department of Genetic Recombination and Segregation, Institute of Cytology and Genetics, Siberian Department of Russian Academy of Science, Lavrentiev Ave, 10, Novosibirsk 630090, Russia. E-mail: aks@bionet.nsc.ru

Received 28 April 2006; Revised 1 August 2006; Accepted 4 September 2006; Published online 27 September 2006.

Abstract

Natural populations of the arctic fox (Alopex lagopus, Canidae, Carnivora) differ drastically in their reproductive strategy. Coastal foxes, which depend on stable food resources, produce litters of moderate size. Inland foxes feed on small rodents, whose populations are characterized by cycling fluctuation. In the years with low food supply, inland fox populations have a very low rate of reproduction. In the years with high food supply, they undergo a population explosion. To gain insight into the genetic basis of the reproductive strategy of this species, we performed complex segregation analysis of the litter size in the extended pedigree of the farmed arctic foxes involving 20 665 interrelated animals. Complex segregation analysis was performed using a mixed model assuming that the trait was under control of a major gene and a large number of additive genetic and random factors. To check the significance of any major gene effect, we used Elston–Stewart transmission probability test. Our analysis demonstrated that the inheritance of this trait can be described within the frameworks of a major gene model with recessive control of low litter size. This model was also supported by the pattern of its familial segregation and by comparison of the distributions observed in the population and that expected under our model. We suggest that a system of balanced polymorphism for litter size in the farmed population might have been established in natural populations of arctic foxes as a result of adaptation to the drastic fluctuations in prey availability.