Population differentiation and gene flow revealed by microsatellite DNA markers in the house mouse (Mus musculus castaneus) in Taiwan

The Expansion of House Mouse Major Urinary Protein Genes Likely Did Not Facilitate Commensalism with Humans

Mouse wild-derived strains (WDSs) combine the advantages of classical laboratory stocks and wild animals, and thus appear to be promising tools for diverse biomedical and evolutionary studies. We employed 18 WDSs representing three non-synanthropic species (Mus spretus, Mus spicilegus, and M. macedonicus) and three house mouse subspecies (Mus musculus musculus, M. m. domesticus, M. m. castaneus), which are all important human commensals to explore whether the number of major urinary protein (MUP) genes and their final protein levels in urine are correlated with the level of commensalism. Contrary to expectations, the MUP copy number (CN) and protein excretion in the strains derived from M. m. castaneus, which is supposed to be the strongest commensal, were not significantly different from the non-commensal species. Regardless of an overall tendency for higher MUP amounts in taxa with a higher CN, there was no significant correlation at the strain level. Our study thus suggests that expansion of the Mup cluster, which appeared before the house mouse diversification, is unlikely to facilitate commensalism with humans in three house mouse subspecies. Finally, we found considerable variation among con(sub)specific WDSs, warning against generalisations of results based on a few strains.

Genetic characterization of F0 outbred and F1 inbred Swiss albino mice using microsatellite markers and their performance evaluation

Swiss albino mice have been widely utilized in various biological researches worldwide. Phenotypic and fitness related traits of F0 and F1 inbred mice were estimated on 918 and 707 individual offsprings, respectively. The influence of fixed effects (litter size and sex) on birth weight (BW), weaning weight (WW) and adult body weight (ABW) in both the generations were found to be statistically significant. Genetic characterization of F0 outbred and the F1 inbred strain of Swiss albino mice were evaluated by using 10 microsatellites markers. The results indicated that total number of alleles per locus ranged from 3 (D2Mit61, D3Mit55, D8Mit14, D9Mit27, D10Mit180, D11Mit167) to 4 (D1Mit15, D2Mit51, D5Mit18, D7Mit323) in F0 and F1 inbred population, with a mean value of 3.4 indicating polymorphism in all 10 loci. The mean of effective number of alleles was 2.935 and 2.733 in F0 and F1 population, respectively. Estimates of the FIS ranged from 0.139 (D10Mit180) to 0.999 (D9Mit27); and from 0.109 (D3Mit55) to 0.679 (D2Mit51) in F0 and F1 inbred population, respectively. The estimated mean markerbased FIS was 0.294 and 0.372 in F0 and F1 populations, respectively. The mean values of observed heterozygosity (Ho) and expected heterozygosity (He) were 0.460 and 0.654, respectively for F0 and 0.390 and 0.627, respectively for F1 inbred mice population. Slight reduction in heterozygosity and 7.8% increase in inbreeding coefficient were observed in F1 inbred in comparison to F0 population. The results suggested that genome wide microsatellite genotyping might be more useful for accurate measuring and reliable estimation of population genetic parameters and inbreeding coefficient.

Heterogeneous road networks have no apparent effect on the genetic structure of small mammal populations

Roads are widely recognized to represent a barrier to individual movements and, conversely, verges can act as potential corridors for the dispersal of many small mammals. Both barrier and corridor effects should generate a clear spatial pattern in genetic structure. Nevertheless, the effect of roads on the genetic structure of small mammal populations still remains unclear. In this study, we examine the barrier effect that different road types (4-lane highway, 2-lane roads and single-lane unpaved roads) may have on the population genetic structure of three species differing in relevant life history traits: southern water vole Arvicola sapidus, the Mediterranean pine vole Microtus duodecimcostatus and the Algerian mouse Mus spretus. We also examine the corridor effect of highway verges on the Mediterranean pine vole and the Algerian mouse. We analysed the population structure through pairwise estimates of FST among subpopulations bisected by roads, identified genetic clusters through Bayesian assignment approaches, and used simple and partial Mantel tests to evaluate the relative barrier or corridor effect of roads. No strong evidences were found for an effect of roads on population structure of these three species. The barrier effect of roads seems to be site-specific and no corridor effect of verges was found for the pine vole and Algerian mouse populations. The lack of consistent results among species and for each road type lead us to believe that the ability of individual dispersers to use those crossing structures or the habitat quality in the highway verges may have a relatively higher influence on gene flow among populations than the presence of crossing structures per se. Further research should include microhabitat analysis and the estimates of species abundance to understand the mechanisms that underlie the genetic structure observed at some sites.

Physiological vagility and its relationship to dispersal and neutral genetic heterogeneity in vertebrates

Vagility is the inherent power of movement by individuals. Vagility and the available duration of movement determine the dispersal distance individuals can move to interbreed, which affects the fine-scale genetic structure of vertebrate populations. Vagility and variation in population genetic structure are normally explained by geographic variation and not by the inherent power of movement by individuals. We present a new, quantitative definition for physiological vagility that incorporates aerobic capacity, body size, body temperature and the metabolic cost of transport, variables that are independent of the physical environment. Physiological vagility is the speed at which an animal can move sustainably based on these parameters. This meta-analysis tests whether this definition of physiological vagility correlates with empirical data for maximal dispersal distances and measured microsatellite genetic differentiation with distance {[F(ST)/[1-F(ST))]/ln distance} for amphibians, reptiles, birds and mammals utilizing three locomotor modes (running, flying, swimming). Maximal dispersal distance and physiological vagility increased with body mass for amphibians, reptiles and mammals utilizing terrestrial movement. The relative slopes of these relationships indicate that larger individuals require longer movement durations to achieve maximal dispersal distances. Both physiological vagility and maximal dispersal distance were independent of body mass for flying vertebrates. Genetic differentiation with distance was greatest for terrestrial locomotion, with amphibians showing the greatest mean and variance in differentiation. Flying birds, flying mammals and swimming marine mammals showed the least differentiation. Mean physiological vagility of different groups (class and locomotor mode) accounted for 98% of the mean variation in genetic differentiation with distance in each group. Genetic differentiation with distance was not related to body mass. The physiological capacity for movement (physiological vagility) quantitatively predicts genetic isolation by distance in the vertebrates examined.

Development of eighteen polymorphic microsatellite markers in Scylla paramamosain by 5' anchored PCR technique

The mud crab Scylla paramamosain plays a significant role in fishery resources in China. In this study, we developed 18 polymorphic microsatellite markers in this important crab by 5' anchored PCR technique. A total of 125 alleles were detected in a single population of 32 individuals of S. paramamosain. The number of alleles per locus ranged from five to nine, with the allele size ranging from 166 to 316 bp. The polymorphism information content (PIC), observed and expected heterozygosity ranged from 0.39 to 0.88, from 0.33 to 0.92 and from 0.42 to 0.86, respectively. Three loci (Scypa13, Scypa14 and Scypa15) deviated significantly from Hardy-Weinberg equilibrium (HWE) after Bonferroni correction (P < 0.0028), and no linkage disequilibrium was found between loci pairs. These polymorphic microsatellite markers will be useful for the study of population genetic structure, construction of genetic linkage maps and mapping of economically quantitative trait loci (QTL) in S. paramamosain.

Dispersal in Mastomys natalensis mice: use of fine-scale genetic analyses for pest management

Mastomys natalensis is the major pest rodent in sub-Saharan Africa. In this study, population genetic techniques were used to gain new insights into its dispersal behaviour, a critical parameter in pest management. Using 11 microsatellites, 272 individuals from a 300 ha area in Tanzania were genotyped. Genetic diversity was high, with no isolation by distance and little differentiation between field plots far apart, indicating a large effective population size and high dispersal rates in agreement with ecological observations. On the other hand, genetic differentiation between nearby field plots, isolation by distance within a single field plot and kin clustering were also observed. This apparent contradiction may be explained by yearly founder effects of a small number of breeding individuals per square area, which is consistent with the presence of linkage disequilibrium. An alternative, not mutually exclusive explanation is that there are both dispersing and sedentary animals in the population. The low-density field plots were characterized by low relatedness and small genetic distances to other field plots, indicating a high turnover rate and negative density-dependent dispersal. In one field plot female-biased dispersal was observed, which may be related to inbreeding avoidance or female competition for resources. Most juveniles appeared to be local recruits, but they did not seem to stay in their native area for more than two months. Finally, possible implications for pest management are discussed.

Microsatellite analysis in two populations of Kunming mice

Kunming mice are the most widely used outbred colony in China. Differences in biological characters and drug reactions among different populations have been observed when using Kunming mice. But the molecular genetic profiles of Kunming mice and the extent of genetic differentiation among populations are unclear. Fifteen microsatellite markers were screened by a fluorescence-based semi-automated genotyping method for the two main populations of Kunming mice from Beijing (BJ) and Shanghai (SH) in China. The observed number of alleles, effective number of alleles, observed heterozygosity, unbiased expected heterozygosity and Shannon information index were used to estimate the genetic variation within the populations. A total of 89 alleles were detected in the two populations, with two to 12 at each locus, and the mean unbiased expected heterozygosity was 0.5724, which implies that there is abundant genetic variation in the populations of Kunming mice. Population differentiation was shown by shared alleles, F-statistics, Nei genetic distance and Nei genetic identity. In population BJ and population SH, respectively, only 35 of 61 and 35 of 63 alleles were shared by both. The Fst per locus varied from 0.0131 (D2Mit30) to 0.5697 (D7Mit281) and the average Fst of all loci was 0.1433, which indicates moderate genetic differentiation between the two Kunming mouse populations. The differences were also observed by Nei's [Genetic distance between populations. Am Nat 1972;106:283-92](1) genetic distance (0.3987) and Nei's [Estimation of average heterozygosity and genetic distance from a small number of individuals. Genetics 1978;89:583-90](2) unbiased measures of genetic distance (0.3881) estimates of subdivision. This research on Kunming mouse genetic diversity will assist in developing a national plan for the unification and standardization of the populations of Kunming mice in China.