The litter size in chromosomally polymorphic blue foxes

Abstract

About 50 % of the Finnish farm bred blue foxes have a Robertsonian translocation in a heterozygous form, whereas the distributions of the homozygous form 2n = 48 and the 2 n = 50 karyotype with two acrocentric autosome pairs seem to be nearly equal. The effect on fertility exerted by the heterozygous Robertsonian translocation was studied on the material from a blue fox farm in Finland during four years. It is concluded that there is a tendency to litter size reduction in mating groups 2n = 49 compared to the 2n = 48 and 2n = 50 mating groups.In this investigation, the 2n = 48 chromosome constitution in parental blue fox groups has every year had a slight tendency to increase the litter size. In addition, the segregation of the karyotypes within the litters of the parental 2n = 49 mating groups is in favour of the 2n = 48 karyotype. Hence, an evolutional tendency towards lower chromosome number without any acrocentric autosomes seems to be indicated.

The telomeric sync model of speciation: species-wide telomere erosion triggers cycles of transposon-mediated genomic rearrangements, which underlie the saltatory appearance of nonadaptive characters

“…About half of them had a Robertsonian translocation in a heterozygous form (2 n  = 49), whereas a quarter were homozygous carriers (2 n  = 48) and a quarter had the original karyotype with two acrocentrics (2 n  = 50). As expected and predicted by genetics, litter size tended to be smaller in mating groups of chromosomal heterozygotes in this study (Makinen and Lohi 1987), in contrast to a previous report (Moller et al 1985) but in line with an older study (Christensen and Petersen 1982). Surprisingly and contrary to the predictions, animals with the Robertsonian translocation in a homozygous form (2 n  = 48) increased over the 4-year span (Makinen and Lohi 1987).…”

“…As expected and predicted by genetics, litter size tended to be smaller in mating groups of chromosomal heterozygotes in this study (Makinen and Lohi 1987), in contrast to a previous report (Moller et al 1985) but in line with an older study (Christensen and Petersen 1982). Surprisingly and contrary to the predictions, animals with the Robertsonian translocation in a homozygous form (2 n  = 48) increased over the 4-year span (Makinen and Lohi 1987). Accordingly, it was observed that matings of two heterozygotes seemed to favor the 2 n  = 48 offspring production (Makinen and Lohi 1987) and the spread of a new chromosomal race.…”

“…Surprisingly and contrary to the predictions, animals with the Robertsonian translocation in a homozygous form (2 n  = 48) increased over the 4-year span (Makinen and Lohi 1987). Accordingly, it was observed that matings of two heterozygotes seemed to favor the 2 n  = 48 offspring production (Makinen and Lohi 1987) and the spread of a new chromosomal race. It was therefore shown that the blue fox displayed an evolutionary tendency towards a lower chromosome number and that the Robertsonian translocation in its homozygous form had a positive effect on fertility.…”