Degree Of Geographic Differentiation Research Articles

Storage protein variability in natural populations of maté (Ilex paraguariensis) in Brazil

ABSTRACT: Samples of 168 maté trees (Ilex paraguariensis) from four natural populations of different states of Brazil (Rio Grande do Sul, Santa Catarina, Paraná and Mato Grosso do Sul) were analyzed for their variability in storage proteins seed, which were used to estimate the degree of differentiation among and within species, because are relatively stable during evolution. Data on band presence/absence from 80 different polypeptides were used to perform similarity coefficient of Jaccard. A high level of genetic variability was reported within sampled populations (SJ intra=0.374). Lower levels of diversity were observed between populations (SJ inter=0.308). Total genetic diversity of maté was Hsp=0.264 estimated by Shannon measure. Partition of that value disclosed that 95 % of the total diversity is within-population, and only 5% to between-populations. The phenogram based on King’s distances indicates a certain degree of geographic differentiation. This represents the first study on storage protein variability in I. paraguariensis and guides the choice of the specimens to increment germoplasm banks and genetic improvement programs.

Novel Y-chromosome short tandem repeats in Sus scrofa and their variation in European wild boar and domestic pig populations.

Y-chromosome markers are important tools for studying male-specific gene flow within and between populations, hybridization patterns and kinship. However, their use in non-human mammals is often hampered by the lack of Y-specific polymorphic markers. We identified new male-specific short tandem repeats (STRs) in Sus scrofa using the available genome sequence. We selected four polymorphic loci (5-10 alleles per locus), falling in one duplicated and two single-copy regions. A total of 32 haplotypes were found by screening 211 individuals from eight wild boar populations across Europe and five domestic pig populations. European wild boar were characterized by significantly higher levels of haplotype diversity compared to European domestic pigs (HD =0.904±0.011 and HD =0.491±0.077 respectively). Relationships among STR haplotypes were investigated by combining them with single nucleotide polymorphisms at two linked genes (AMELY and UTY) in a network analysis. A differentiation between wild and domestic populations was observed (FST =0.229), with commercial breeds sharing no Y haplotype with the sampled wild boar. Similarly, a certain degree of geographic differentiation was observed across Europe, with a number of local private haplotypes and high diversity in northern populations. The described Y-chromosome markers can be useful to track male inheritance and gene flow in wild and domestic populations, promising to provide insights into evolutionary and population genetics in Sus scrofa.

Genotypic diversity and migration patterns of Phytophthora infestans in the Nordic countries

In this study we investigated the genotypic diversity and the migration patterns of Phytophthora infestans in the Nordic countries. Isolates of P. infestans from outbreaks in 43 fields sampled in 2008 were collected using stratified sampling with country, field, and disease foci as the different strata. Microsatellites were used as markers to determine the genotypic variation in the sampled material. The results show a high genotypic variation of P. infestans in the Nordic countries with most of the genotypes found only once among the collected isolates. The major part of the genotypic variation was observed within the fields, with low differentiation between the fields. The observed low association of alleles among loci is consistent with frequent sexual reproduction of P. infestans in the Nordic countries. Coalescence analyses did not support a single common population for the four countries, thus indicating some degree of geographic differentiation. The analyses of migration patterns showed differing levels of gene flow among the Nordic countries. No correlation between migration rates and geographical distance could be seen. This could be explained by different degrees of genetic similarity between the pathogen populations in the different countries.

Phylogeography of North Atlantic intertidal tardigrades: refugia, cryptic speciation and the history of the Mid-Atlantic Islands

Aim To analyse the phylogeographical history of intertidal tardigrades in the North Atlantic in order to improve our understanding of geographical differentiation in microscopic organisms, and to understand the potential importance of the Mid-Atlantic Islands as stepping stones between the American and European coasts of the Atlantic Ocean. Location Twenty-four localities from the Mid-Atlantic Islands (Greenland, Iceland and the Faroe Islands) and both sides of the North Atlantic Ocean. Methods A mitochondrial marker (cytochrome c oxidase subunit I) was sequenced from individual tardigrades belonging to the genus Echiniscoides. The existence of cryptic species was detected using generalized mixed Yule coalescence analysis; lineage ages were estimated with relaxed clock methods; and the degree of geographical differentiation was analysed with samova analyses, haplotype networks and Mantel tests. Results Echiniscoides hoepneri, previously known only from Greenland, was recovered throughout the Mid-Atlantic Islands. The Faroe Islands population was isolated from Greenland and Iceland, but overall genetic variation was low. The morphospecies Echiniscoides sigismundi had high genetic variation and consisted of at least two cryptic species. A northern and a southern species were both recovered on both sides of the Atlantic, but only the northern species was found on the Mid-Atlantic Islands. The northern species showed signs of long-term isolation between the Western and Eastern Atlantic, despite the potential of the Mid-Atlantic islands to act as stepping-stones. There was no sign of long-term isolation in the southern species. The Mid-Atlantic individuals of the northern species were of Eastern Atlantic origin, but Greenland and Iceland showed signs of long-term isolation. The genetic pattern found in the southern species is not clearly geographical, and can probably be best explained by secondary contact between former isolated populations. Main conclusions North Atlantic intertidal tardigrades from the genus Echiniscoides showed strong geographical differentiation, and the Mid-Atlantic Islands seemed unimportant as stepping stones across the Atlantic. The geographical variation of the northern species of E. sigismundi suggests post-glacial recolonization from several refugia.

Diversity of five novel Y-STR loci and their application in studies of north Chinese populations

Y-chromosomal short tandem repeats (Y-STRs) show sufficient variability among individuals in a population and high degree of geographical differentiation, so their polymorphic character makes them especially suited for population genetic studies. In this study, five novel Y-STR loci were analysed in 174 samples from five minority populations residing in north China (Daur, Kazak, Xibe, Uighur and Kirgiz) to determine the diversity of these loci in north China and to evaluate their usefulness in population study. Ninety-seven haplotypes were constructed, with 30 in Daur, 24 in Kazak, 28 in Uighur, 27 in Xibe and 16 in Kirgiz. Sixty-six (68.04%) of them were unique. The R(ST) showed that there was no significant difference in Daur and Xibe (R(ST) = 0.02231, P > 0.05), while among the Kazak, Uighur and Kirgiz, who reside in northwest China, there were significant differences. These results showed that these five Y-STR loci were polymorphic in the five populations. The results of AMOVA showed that majority of the differences were found within populations. By RST, the relationships of the five populations were accordance with the historical records: Xibe migrated to Xinjiang during the Qing dynasty, and Kazak, Uighur and Kirgiz have different ancestors.

Genetic diversity of Chinese Spring Soybean Germplasm Revealed by SSR Markers

AbstractTo use, maintain and increase crop germplasm collections efficiently, it is important to assess the diversity of these collections. In this study, 1383 accessions of Chinese spring sowing soybean (Glycine max) were used for SSR analysis. In total, 1111 alleles were detected among these collections with an average number of alleles (NA) of 18.52 per locus. The genetic diversity index (PIC value) varied from 0.456 to 0.928 with an average of 0.815. Intensive breeding of cultivars have led to a decrease of genetic diversity. Random‐repeated sampling within landraces of different geographical regions suggested that the ranking of both average NA and PIC values among different geographical regions were North spring soybean (Nsp) > South spring soybean (Ssp) > Northeast spring soybean (NEsp), but because of the uneven distribution of SSR variation patterns, the differences between them did not reach a significant level. There was a relationship between genetic distances and geographical distances among soybean populations from different regions, indicating a certain degree of geographical differentiation among Chinese soybean germplasm collections.

Allozymic polymorphism and genetic differentiation among populations of Calomys musculinus and Calomys laucha (Rodentia: Muridae) from eastern Argentina

Summary The genetic variability and divergence among natural populations of Calomys musculinus and C. laucha from eastern Argentina were examined by protein electrophoresis of 24 loci. High levels of genetic variability were found in both species when compared to other rodents and mammals. Mean expected heterozygosity (He) ranged from 0.112 to 0.156, proportion of polymorphic loci (P 95% ) from 37.5% to 50% and mean number of alleles per locus (A) of 1.6-1.7 for C. musculinus . H e from 0.097 to 0.126, P 95% from 34.8 to 39.1 and A from 1.7 to 1.9 were the values for C. laucha . Populations of this last species revealed a higher degree of geographical differentiation (Θ = 0.017, P C. musculinus (Θ = 0.002, P > 0.05). These results are in agreement with the known social structure and habitat of both species. C. musculinus is an opportunistic species, with a loose social structure and a predominance of transient over resident animals, indicating a high ambulatory activity. C. laucha , on the contrary, inhabits almost exclusively cultivated fields, and evidence of social stratification has been reported for this species.

Genetic variation in the Old World screw-worm fly,Chrysomya bezziana(Diptera: Calliphoridae)

AbstractThe Old World screw-worm fly,Chrysomya bezzianaVilleneuve, occurs in Africa, the Middle East, Malaysia, Indonesia and Papua New Guinea, but it is not found in Australia. Introduction into Australia from any of these source areas would threaten the viability of much of the grazing industry in the northern part of the continent. Proposed control by the sterile insect release method (SIRM) would be compromised by the existence of sibling species withinC. bezziana.This study examines the degree of genetic differentiation throughout the extensive range of the fly to assess if the degree of geographic differentiation indicates the existence of sibling species and, allows identification of the source of any introduced flies. Electrophoretic analysis of 23 loci from samples collected in southern Africa, the Middle East, Malaysia, Indonesia, and Papua New Guinea revealed 11 polymorphic loci. Overall, populations show remarkably little divergence given the geographic distribution of sample sites. None of the populations sampled were fixed for alternative electromorphs. There is no evidence from this study for the presence of sibling species withinC. bezziana.

Adaptive significance of amylase polymorphism in Drosophila I. The geographical pattern of allozyme polymorphism at the amylase locus in Drosophila subobscura

Allelic variation at the Amy locus was studied in eight natural populations from the central and northern range of D. subobscura, and the geographical pattern of Amy polymorphism over the range of this species was described. Even though regional and local differences in gene frequencies were found, in general the same alleles occur at high, intermediate and low frequencies, in nearly all populations. There are no significant differences in allele frequencies, but there is significant difference in the degree of heterozygosity among groups of populations from the northern, central and southern range. An analysis of population subdivision indicates that heterogeneity within populations is higher than between populations. Genetic distance values indicate that there is a variable degree of geographical differentiation between local populations. Variability within and between continental and insular populations is also discussed.

TEMPORAL STABILITY OF LACTATE DEHYDROGENASE-A CLINES OF THE HIGH COCKSCOMB, ANOPLARCHUS PURPURESCENS.

In marine species with planktonic larval stages, strong geographic differentiation among resident adult populations is noteworthy in that identification of the forces and mechanisms which create such local differentiation allows an assessment of the relative importance of natural selection in promoting genetic divergence. Williams et al. (1973), and later Koehn and Williams (1978), focused on this problem in their analysis of genetic differentiation in the American eel, Anguilla rostrata. Their study centered on the interaction between age-dependent differentiation (elvers vs. resident adults) and spatial differentiation of groups along a latitudinal transect. They found different patterns of differentiation which depended upon the specific genetic marker under analysis. At the Mdh locus, allele frequencies were homogeneous among age-groups and among localities, suggesting recruitment of elvers from a common zygotic pool with no subsequent divergence between groups of colonists in situ. In contrast, at the Sdh locus, they observed a significant spatial component of variation across latitude, but one which was equally pronounced in both age groups. This result suggested (in light of the life history of the American eel) that divergence occurred prior to larval recruitment and was not further accentuated in situ. Finally, at the Phi-II locus, they observed that allele frequencies of newly recruited larvae were uniform across the transect (once again suggesting a common zygotic pool), but that geographic differentiation of adults was significant. This latter pattern would be consistent with a predominant role of local selective factors in promoting genetic divergence and it suggested selection intensities of about 10% per generation. Although the power of their analysis lies largely in the peculiar migrational history of the American eel, there is no reason to believe that the differences in genetic composition between life stages observed by Williams et al. (1973) and Koehn and Williams (1978) are in any way unique to Anguilla. As they point out, it is reasonable to expect that age-specific selection would operate in other species with planktonic larvae, but similar analyses have been rarely conducted. Actually, the degree of geographic differentiation in the American eel is rather slight; for example, systematic variation in Phi-II allele frequencies is on the order of 5% per degree of latitude (Koehn and Williams, 1978). In other marine fishes with planktonic larvae, more pronounced examples of geographic variation are known. In Anoplarchus purpurescens, an intertidal blennioid fish of the northwestern Pacific Ocean, relatively sharp differences in allele frequency over short distances have been reported (Johnson, 1971, 1977; Sassaman and Yoshiyama, 1979; Yoshiyama and Sassaman, unpubl.). Here we explore temporal (age-group) aspects of allele-frequency variation along two pronounced gradients of gene-frequency change in Anoplarchus. Our analysis follows the same logical format of Williams et al. (1973) and Koehn and Williams (1978). In addition we examine yearto-year stability of these gene-frequency clines by reference to previously published information (Johnson, 1971; Sassaman and Yoshiyama, 1979) for the same sampling sites. Since the presumption of extensive