Analysis on Genetic Diversity and Isolation Mechanism by Distance of Different Ecological Type Sheep Breeds in Mon-golia Sheep Group

In the present study with Tan sheep, small-tailed Han sheep, Hu sheep, Tong sheep, and Wadi sheep, we detected the distribution of gene frequency of several microsatellite sites in different chromosomes, the result showed that： 1） Hu sheep was in the status of Hardy-Weinberg extreme disequilibrium （P 〈 0.01）, while populations including Tong sheep, small-tailed Han sheep, Tan sheep, and Wadi sheep were in Hardy-Weinberg equilibrium （P 〉 0.05）. 2） Variance analysis of the heterozygosity and poly- morphic information content at rnicrosatellite makers showed that there were not significant differences among populations as to heterozygosity and PIC （P 〉 0.05）, as to effective number of alleles there were not significant differences both among Tan sheep, Hu sheep, Tong sheep, and Wadi sheep, and between Wadi sheep and small-tailed sheep （P 〉 0.05）, but between the former three populations and the latter two populations, there were significant differences （0.01〈 P 〈0.05）. The variation levels of small-tailed Han sheep was the highest in the five populations based on microsatellite maker data, subsequently followed by Wadi sheep, Tong sheep, Tan sheep, and then Hu sheep. 3） The phylogenetic relationships of the five sheep populations in this study did not meet the mechanism of isolation by distance, and the genetic differentiation relationships among five sheep populations were not closely linearly correlative with their geography distribution. Our findings supported related records in literature： The five populations originated on different time stage from the primogenitor population and communicated genetically with each other thereafter in the process of natural and artificial selection and on different ecological environment.

The Distribution of Surnames in Xiantao City through Isonymy

The population migration in Hubei Province was frequent in history,accompanied by the migration of surnames,so it is important to study their population surnames.We take Xiantao City as an example to explore the isonymic structure of small and medium-sized cities in Hubei.The surname distributions of 223327 residents registered in 2013 were analyzed in 5 towns and 105 villages of Xiantao.The number of different surnames found was 422.As for surnames,theα-value reflects the influence of ethnic composition on the abundance of surnames.The correlation between the isonymic distance and the geographic distance between villages was calculated and indicated that Euclidean distance was weakly correlated with the geographic distance(r=0.177±0.012),and the isonymic distance increased with the geographical distance.Furthermore,the dendrogram and PCA built from the matrix of Euclidean distances between villages identified a main surname differentiation between the urban and rural areas.

Genomic differentiation with isolation by distance along a latitudinal gradient in the spotted-leg treefrog Polypedates megacephalus

The patterns of isolation by distance(IBD)entailing increased genetic differentiation among populations have aroused extensive concerns for evolutionary biologists.Although the IBD may act on spatial processes contribut-ing to the genetic differentiation among populations in anuran species,the factors shaping the IBD of frogs among populations in natural systems are largely unknown.Here,we studied the genetic differentiation among six popula-tions with 24 individuals of the spotted-leg treefrog along a latitudinal gradient(1860.31 km)based on 1020 single nucleotide polymorphisms from restriction site-associated DNA sequencing.The results showed that the genetic diversity differed significantly among populations and that the insular populations had higher genetic diversity than the mainland populations.Furthermore,we also found a significant genetic differentiation among populations(FST=0.277)and no sign of inbreeding(FUNI=-0.145).The IBD was detected for all populations,and a higher degree of the IBD was indicated when controlling for the effects of the isolation between Hainan and mainland populations caused by the Qiongzhou Strait.Ourfindings suggest that the form of the Qiongzhou Strait plays a key role in shaping the genetic diversity and population differentiation in treefrogs.

Temperature and precipitation,but not geographic distance,explain genetic relatedness among populations in the perennial grass Festuca rubra

Aims Knowledge of genetic structure of natural populations and its determinants may provide key insights into the ability of species to adapt to novel environments.In many genetic studies,the effects of climate could not be disentangled from the effects of geographic proximity.We aimed to understand the effects of temperature and moisture on genetic diversity of populations and separate these effects from the effects of geographic distance.We also wanted to explore the patterns of distribution of genetic diversity in the system and assess the degree of clonality within the populations.We also checked for possible genome size variation in the system.Methods We studied genetic variation within and among 12 populations of the dominant grass Festuca rubra distributed across a unique regional-scale climatic grid in western Norway,Europe and explored the importance of temperature,precipitation and geo-graphic distance for the observed patterns.We also explored the distribution of genetic diversity within and among popula-tions,identified population differentiation and estimated degree of clonality.The analyses used microsatellites as the genetic marker.The analyses were supplemented by flow cytometry of all the material.Important Findings All the material corresponds to hexaploid cytotype,indicating that ploidy variation does not play any role in the system.The results indicate that temperature and precipitation were better predictors of genetic relatedness of the populations than geographic distance,suggesting that temperature and precipitation may be important determinants of population differentiation.In addition,precipitation,alone and in interaction with temperature,strongly affected population genotypic diversity suggesting increased clonality towards the coldest and especially the coldest wettest climates.At the same time,individuals from the coldest and wettest climates also had the high-est individual genetic diversity,suggesting that only the most hetero-zygous individuals survive under these harsh climates.Most of the genetic variation was distributed within populations,suggesting that most populations have sufficient genetic diversity to adapt to novel climatic conditions.The alpine populations,i.e.populations which are likely the most endangered by climate change,however,lack this potential due to the high levels of clonality as detected in our study.

Spatial isolation and genetic differentiation in naturally fragmented plant populations of the Swiss Alps

The effect of anthropogenic landscape fragmentation on the genetic diversity and adaptive potential of plant populations is a major issue in conservation biology.However,little is known about the partitioning of genetic diversity in alpine species,which occur in naturally fragmented habitats.Here,we investigate molecular patterns of three alpine plants(Epilobium fleischeri,Geum reptans and Campanula thyrsoides)across Switzerland and ask whether spatial isolation has led to high levels of population differentiation,increasing over distance,and a decrease of within-population variability.We further hypothesize that the contrasting potential for long-distance dispersal(LDD)of seed in these species will considerably influence and explain diversity partitioning.Methods For each study species,we sampled 20–23 individuals from each of 20–32 populations across entire Switzerland.We applied Random Amplified Polymorphic Dimorphism markers to assess genetic diversity within(Nei’s expected heterozygosity,He;percentage of polymorphic bands,Pp)and among(analysis of molecular variance,Ust)populations and correlated population size and altitude with within-population diversity.Spatial patterns of genetic relatedness were investigated using Mantel tests and standardized major axis regression as well as unweighted pair group method with arithmetic mean cluster analyses and Monmonier’s algorithm.To avoid known biases,we standardized the numbers of populations,individuals and markers using multiple random reductions.We modelled LDD with a high alpine wind data set using the terminal velocity and height of seed release as key parameters.Additionally,we assessed a number of important life-history traits and factors that potentially influence genetic diversity partitioning(e.g.breeding system,longevity and population size).Important findings For all three species,we found a significant isolation-by-distance relationship but only a moderately high differentiation among populations(Ust:22.7,14.8 and 16.8%,for E.fleischeri,G.reptans and C.thyrsoides,respectively).Within-population diversity(He:0.19–0.21,Pp:62–75%)was not reduced in comparison to known results from lowland species and even small populations with<50 reproductive individuals contained high levels of genetic diversity.We further found no indication that a high long-distance seed dispersal potential enhances genetic connectivity among populations.Gene flow seems to have a strong stochastic component causing large dissimilarity between population pairs irrespective of the spatial distance.Our results suggest that other life-history traits,especially the breeding system,may play an important role in genetic diversity partitioning.We conclude that spatial isolation in the alpine environment has a strong influence on population relatedness but that a number of factors can considerably influence the strength of this relationship.

Investigation of the co-existing interference between TD-MBMS and TD-SCDMA/TD-HSDPA

TD-MBMS is the abbreviation of time division-synchronous code division multiple access （TD-SCDMA） multimedia broadcast and multicast service （MBMS）,which was introduced in the release 6 of universal mobile telecommunications system （UMTS） in order to deliver multimedia data more efficiently. Since TD-MBMS may work on the same time slot （TS） of the same frequency with TD-SCDMA and time division-high speed downlink packet access （TD-HSDPA） as described in the unified timeslot networking （UTN） strategy,the work of co-existing interference analysis is an important research filed. This article firstly analyzes theoretically the co-existing interference between TD-MBMS and TD-SCDMA/TD-HSDPA. Then,system level simulation is used to quantify the co-existing interference under different scenarios considering the transmit power of TD-MBMS and TD-HSDPA and the load factor of TD-SCDMA network. Simulation results show that TD-SCDMA/TD-HSDPA has little impact on the TD-MBMS while the interference from TD-MBMS to TD-SCDMA/TD-HSDPA is more serious and the corresponding isolation distance is then suggested. The results are useful for radio network planning and optimization of TD-SCDMA.

Restricted dispersal determines fine-scale spatial genetic structure of Mongolian gerbils

Restricted gene flow may cause positive spatial genetic autocorrelation of animal populations at fine spatial scales. The Mongolian gerbil Meriones unguiculatus is a territorial, social rodent. Territoriality may create social fences to restrict dispersal or gene flow of Mongolian gerbils to a short distance. Restricted dispersal may differentiate fine-scale spatial genetic structure of populations with increasing distances （i.e., isolation by distance [IBD]）. Competition for mates and inbreeding avoidance may result in equal dispersal propensity and subsequently similar spatial genetic autocorrelation between males and females of monogamous gerbils. We genotyped 327 gerbils, live captured from 26 burrow systems on a 9-ha plot in northcentral Inner Mongolia, China, using seven microsateliite loci. Spatial genetic autocorrelation was positive within 80 m and became negative from 80 m to 200 m, suggesting restricted gene flow. Inter-group genetic and geographic distances were related positively, supporting the IBD model. Live trapping data demonstrated equal dispersal propensities of male and female gerbils. Restricted dispersal and social organization may determine fine-scale spatial population genetic structure of social rodents.

Taxonomic status of Chinese blue sheep(Pseudois nayaur):new evidence of a distinct subspecies

The blue sheep is an endemic species to the Qinghai-Tibet Plateau and surrounding regions.It has been regarded as having 2 subspecies:Pseudois nayaur nayaur and P.n.szechuanensis.However,such a classification remains controversial.Herein,we analyze 10 microsatellite loci and part of the mitochondrial control region for clarification in such taxonomic debates.We use samples from 168 individuals from 6 geographic populations covering almost all the distribution areas of the species in China to carry out comparisons.Phylogenetic trees derived from both the microsatellite and mitochondrial markers combined with the discriminant analysis of principal components(DAPC)and the STRUCTURE analysis reveal that the individuals in the Helan Mountains are well grouped with a distinct evolutionary lineage and are significantly different from the other populations of P.n.szechuanensis according to Fst values,implying that this isolated population should be categorized as a valid subspecies;namely,Pseudois nayaur alashanicus.The isolation-by-distance(IBD)analysis shows a significant positive relationship between genetic and geographical distances among the populations.

A statistical procedure to assess the significance level of barriers to gene flow

Although several methods are available to study the extent of isolation by distance （IBD） among natural populations, comparatively few exist to detect the presence of sharp genetic breaks in genetic distance datasets. In recent years, Monmonier＇s maximum-difference algorithm has been increasingly used by population geneticists. However, this method does not provide means to measure the statistical significance of such barriers, nor to determine their relative contribution to population differentiation with respect to IBD. Here, we propose an approach to assess the significance of genetic boundaries. The method is based on the calculation of a multiple regression from distance matrices, where binary matrices represent putative genetic barriers to test, in addition to geographic and genetic distances. Simulation results suggest that this method reliably detects the presence of genetic barriers, even in situations where IBD is also significant. We also illustrate the methodology by analyzing previously published datasets. Conclusions about the importance of genetic barriers can be misleading if one does not take into consideration their relative contribution to the overall genetic structure of species.