We reviewed the distribution of Robertsonian (Rb) races of Mus musculus domesticus in central and southern Italy. This Rb system is called the Apennine system and includes four races (Cittaducale, ICDE, 2n=22; Ancarano, IACR, 2n=24; Campobasso, ICBO, 2n=22; Colfiorito, ICOL, 2n=33–34) surrounded by standard populations with karyotype 2n=40. Here we evaluate the relationships between the altitudinal distribution of races, and the indoor vs. outdoor behaviour of populations, inferred from literature data on the diet of the barn owl Tyto alba. We assume that a higher prevalence of mice in owl pellets reflects a higher outdoor occurrence of mice. The IACR and ICDE races were found at higher altitudes than the standard populations, while the ICBO race is present at lower altitudes like the standard race. The standard race has indoor and outdoor populations; in all the Rb races an indoor life has been suggested by our data. This behaviour is only partly due to altitude, since the ICBO race also lives at sea level. We speculated that indoor life is an intrinsic characteristic of the ICBO race irrespective of the environment. This pattern reinforces the idea that indoor life, through its population dynamics, has played a significant role in the evolutionary history of Rb races.
Genetic variation among populations of commensal house mice was studied across the territories of the Czech and Slovak Republics and in some adjacent areas of Germany. We used six diagnostic allozyme loci (Es-2, Gpd-1, Idh-1, Mpi, Np, Sod-1) and the following molecular markers: B1 insertion in the Btk gene (X chromosome), Zfy2 18-bp deletion (Y chromosome), BamH I restriction site in the mt-Nd1 gene (mtDNA) and Hba-4ps 16-bp insertion (diagnosing the presence of t haplotypes). In total, 544 individuals taken from 49 localities were examined. Almost the entire territories of the Czech Republic and Slovakia were found to be occupied by Mus musculus, the only exception being the westernmost parts of the Czech Republic, where M. musculus meets the range of M. domesticus and forms a narrow belt of hybrid populations. Despite this, domesticus-type alleles of some allozyme markers (notably Es-2) were also found at sites well within the range of M. musculus, either tens or hundreds of kilometres behind the hybrid zone. This provides evidence of either: (1) introgression of some markers into the species’ genome due to free gene flow through the zone, or (2) human-mediated long-distance migrations, or (3) incomplete lineage sorting. Conversely, variants of molecular markers typical for M. domesticus in Btk, Zfy2 and mt-Nd1were only found in the westernmost populations studied. t haplotypes were quite frequent in some populations, irrespective of whether M. domesticus, M. musculus or their hybrids, yet no t/t homozygotes were found. The mean frequency of t/+ heterozygotes found within the study populations was 13%.
We analyzed sequences of two variable segments of the mitochondrial control region (CR) and flanking regions in the house mouse (Mus musculus). Most of the material was sampled from the eastern Mediterranean and the Middle East, i.e., a source area for the colonization of Europe. These sequences were supplemented with other samples from the whole range of the species including the Yemeni island of Socotra. This island was shown to harbour mice bearing M. m. domesticus and M. m. castaneus CR haplotypes. In addition, we found 10 distinct sequences at the same locality that were markedly different from all known CR sequences. Sequencing of the whole mitochondrial genome suggested these sequences to represent nuclear fragments of the mitochondrial origin (numts). We assessed genetic variation and phylogeography within and among the house mouse subspecies and estimated the substitution rate, coalescence times, and times of population expansion. We show the data to be consistent with time dependency of substitution rates and recent expansion of mouse populations. The expansion of European populations of M. m. musculus and M. m. domesticus estimated from the CR sequences coincide with presumed time of colonization of the continent in the Holocene.
Two chromosomal races of the house moue occur in central Tunisia: a standard type (2n = 40) and a Robertsonian race (2n = 22). Although contact between races is not restricted, hybrid populations are rare. Patterns of mate preference between wild mice of the two races suggest that, although incipient, this premating divergence could limit the number of crosses between races in nature. In this paper we compare sexual preference of laboratory-born mice and their parents caught as adults in the wild with the aim to assess whether the social context of development to adulthood could influence expression of preference. We predict that in the absence of such influence, parents and laboratory-born offspring should show a comparable pattern of preference. Results show that offspring preference is always lower than and not related to that of their parents. However, a significant pair effect exist leading us to group parents and offspring into three categories according to the parents' preference: homokaryotypic, heterokaryotypic, or dissimilar. Offspring exhibit a preference, which is consistent with that of their parents, only in two cases: male offspring of the standard race when both parents show a heterokaryotypic preference; all offspring when the homokaryotypic preference of fathers is high. Discrepancy between preferences of wild-caught mice and their laboratory-born progeny suggests that, here, preference may be partly influenced by social conditions experienced before and during adulthood.