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At least 883 records · Page 49Linked to original sources
PubMed2005

[Population structure of the Baikalian amphipod Gmelinoides fasciatus (Stebbing)].

Using the data on 71 individual sequences of the gene for the mitochondrial cytochrome-c-oxidase subunit one, molecular and phylogenetic characterization of the Baikalian amphipod, Gmelinoides fasciatus (Crustacea, Amphipoda), was performed. Interspecific polymorphism was demonstrated. Four main amphipod populations, Southeastern, Southwestern, Northern, and Central, were distinguished. A low level of genetic diversity typical of Southwestern population was revealed. For its explanation, the bottleneck hypothesis was proposed.

Amphipoda↗
PubMed2004

Effects of culturing on the population structure of a hyperthermophilic virus.

The existence of a culturing bias has long been known when sampling organisms from the environment. This bias underestimates microbial diversity and does not accurately reflect the most ecologically relevant species. Until now no study has examined the effects of culture bias on viral populations. We have employed culture-independent methods to assess the diversity of Sulfolobus spindle-shaped viruses (SSVs) from extremely hyperthermal environments. This diversity is then compared to the viral diversity of cultured samples. We detected a clear culturing bias between environmental samples and cultured isolates. This is the first study identifying a culture bias in a viral population.

Archaeal Viruses↗
PubMed1996

Population structure of the yellow-footed rock-wallaby Petrogale xanthopus (Gray, 1854) inferred from mtDNA sequences and microsatellite loci.

The yellow-footed rock-wallaby Petrogale xanthopus is considered to be potentially vulnerable to extinction. This wallaby inhabits naturally disjunct rocky outcrops which could restrict dispersal between populations, but the extent to which that occurs is unknown. Genetic differences between populations were assessed using mitochondrial DNA (control region) sequencing and analysis of variation at four microsatellite loci among three geographically close sites in south-west Queensland (P. x. celeris) and, for mtDNA only, samples from South Australia (P. x. xanthopus) as well. Populations from South Australia and Queensland had phylogenetically distinct mtDNA, supporting the present classification of these two groups as evolutionarily distinct entities. Within Queensland, populations separated by 70 km of unsuitable habitat differed significantly for mtDNA and at microsatellite loci. Populations separated by 10 km of apparently suitable habitat had statistically homogeneous mtDNA, but a significant difference in allele frequency at one microsatellite locus. Tests for Hardy-Weinberg equilibrium and microgeographical variation at microsatellite loci did not detect any substructuring between two wallaby aggregations within a colony encircling a single rock outcrop. Although the present study was limited by small sample sizes at two of the three Queensland locations examined, the genetic results suggest that dispersal between colonies is limited, consistent with an ecological study of dispersal at one of the sites. Considering both the genetic and ecological data, we suggest that management of yellow-footed rock-wallabies should treat each colony as an independent unit and that conservation of the Queensland and South Australian populations as separate entities is warranted.

Alleles↗
PubMed2006

mtDNA variation in Inuit populations of Greenland and Canada: migration history and population structure.

We examined 395 mtDNA control-region sequences from Greenlandic Inuit and Canadian Kitikmeot Inuit with the aim of shedding light on the migration history that underlies the present geographic patterns of genetic variation at this locus in the Arctic. In line with previous studies, we found that Inuit populations carry only sequences belonging to haplotype clusters A2 and D3. However, a comparison of Arctic populations from Siberia, Canada, and Greenland revealed considerable differences in the frequencies of these haplotypes. Moreover, large sample sizes and regional information about birthplaces of maternal grandmothers permitted the detection of notable differences in the distribution of haplotypes among subpopulations within Greenland. Our results cast doubt on the prevailing hypothesis that contemporary Inuit trace their all of their ancestry to so-called Thule groups that expanded from Alaska about 800-1,000 years ago. In particular, discrepancies in mutational divergence between the Inuit populations and their putative source mtDNA pool in Siberia/Alaska for the two predominant haplotype clusters, A2a and A2b, are more consistent with the possibility that expanding Thule groups encountered and interbred with existing Dorset populations in Canada and Greenland.

Canada↗
PubMedDate not supplied

Population structure and blood genetics of the Pacaás Novos Indians of Brazil.

Two communities of relatively recently contacted Brazilian Indians, the Pacaás Novos, have been studied in relation to several demographic parameters and 28 genetic systems. The age and sex distribution, fertility and mortality patterns were not very distinct in the two populations, but they differed markedly in relation to the mating, migration and genetic data (six of the 19 variable loci showed differences higher than 10%). This was interpreted as being the consequence of a fission event, one of the many that may periodically occur, sometimes followed by fusions, in populations at this cultural level. The Pacaás Novos also show some distinctive features when previous genetic studies of South American Indians are reviewed, eight alleles of the variable 19 (LMS, R2, R0, Se, Hp1, Gm1,2;21, Gc1F and PGM1(1)), presenting differences varying between 12%-34% from the average obtained considering these earlier investigations.

Adolescent↗
PubMed2006

No evidence of population structure across three isolated subpopulations of Russula brevipes in an oak/pine woodland.

Russula brevipes is common ectomycorrhizal (EM) fungus that is associated with several hosts across temperate forest ecosystems. A previous study has demonstrated that substructuring across large geographic distances (1500 km) occurs in the western USA. To examine genetic structure over a more localized scale, basidiocarps of Russula brevipes from three subpopulations, separated by distances of 230-1090 m, were collected over two consecutive years in an oak/pine woodland. Microsatellite loci were used to test for population differentiation both among subpopulations and by year. No significant population differentiation was detected between subpopulations (theta(ST) = 0.01) or between years (theta(ST) = 0.01). Most loci were consistent with a Hardy-Weinburg equilibrium and 82% of the genets between seasons from similar sampling localities constituted new genotypes. These results indicate that R. brevipes constitutes a randomly mating population with no genetic differentiation between locations or across successive fruiting seasons.

Agaricales↗
PubMed2000

Population structure of long-finned pilot whales in the North Atlantic: a correlation with sea surface temperature?

The long-finned pilot whale, Globicephala melas, is a social, pelagic odontocete distributed widely in the cold temperate waters of the North Atlantic. Despite genetic, morphometric, physiological and observational studies, it remains unclear whether any population substructure exists. We have used eight highly polymorphic microsatellite loci to analyse samples from four disparate sampling sites: USA East Coast (Cape Cod), West Greenland, the Faeroe Islands and the UK. Our results indicate that substructure does exist, and is particularly pronounced between West Greenland and other sites. The magnitudes of the various pairwise comparisons do not support a simple isolation-by-distance model. Instead, the patterns of genetic differentiation suggest that population isolation occurs between areas of the ocean which differ in sea surface temperature. Such a mechanism is supported by the observation that temperature is a primary factor determining the relative distributions of two short-finned pilot whale (G. macrorhynchus) populations off the Pacific coast of Japan.

Animals↗
PubMed2001

Population structure and genetic diversity of Botrychium pumicola (Ophioglossaceae) based on inter-simple sequence repeats (ISSR).

Species of Botrychium reproduce by spores that form subterranean gametophytes and a few, like B. pumicola, also reproduce asexually with subterranean sporophytic gemmae. The goal of this study was to examine the genetic diversity of B. pumicola populations and to better understand the role of gemmae. Ninety-nine individuals from three monitored populations were sampled. The technique of inter-simple sequence repeats (ISSR) produced 15 polymorphic loci and identified 71 ISSR genotypes. Sixteen of the ISSR genotypes were shared by more that one individual in a population, representing potential clones. Ten of the 16 shared genotypes were not limited to clusters of plants (groups of plants growing from the same point). The ten potential clones were disjunct (separated by other genotypes) and not in patches as might be expected for an underground propagule. There is a high probability that these shared genotypes arose from independent sexual events suggesting they were not clones. These results suggest that the long-distance dispersal of gemmae is at best a rare event.

Journal Article↗
PubMedDate not supplied

[The influence of population structure on systemic antibiotic consumption. Valladolid, Spain].

BACKGROUND: The high degree to which systemic antibiotics are consumed in our country makes a study of those factors determining the spread thereof necessary. Different parameters are involved in the unequal spread of their consumption, including: a) the epidemiology of the infectious processes b) the population-dependent factors and c) factors depending upon the prescribing physicians. This study is aimed at analyzing those determining factors depending upon the population (type of population and age). METHODS: A longitudinal retrospective study based on systemic antibiotic consumption data provided by the company International Marketing Services (IMS) for the January 1, 1996-December 31, 2000 period. The consumption indicator used was the number of daily doses defined per 1000 inhabitants/day (DID). Six geographical areas in the province of Valladolid were placed under study, three of which were urban and the other three mainly rural. RESULTS: The overall consumption by area was as follows: Medina del Campo (25.9DID), the capital city of Valladolid (23.4DID), Laguna de Duero (22.6DID), Northern Area (22.4DID), Southern Area (21.4DID) and, lastly, the Central Area (20.2DID). The specific consumption by areas revealed a greater consumption of amoxicillin in the three urban areas, amoxicillin-clavulanic acid and the major macrolides in Medina del Campo, quinolone antibiotics in the Northern Area and tetracyclines and sulfonamides in the capital city of Valladolid. CONCLUSIONS: Major overall consumption-related differences were found to exist among areas, the maximums being found in the urban areas. These differences were more marked on when studying the geographic spread of the consumption of the main active ingredients.

Adolescent↗
PubMed2000

Effects of population structures and selection strategies on the purging of inbreeding depression due to deleterious mutations.

Stochastic simulations were run to compare the effects of nine breeding schemes, using full-sib mating, on the rate of purging of inbreeding depression due to mutations with equal deleterious effect on viability at unlinked loci in an outbred population. A number of full-sib mating lines were initiated from a large outbred population and maintained for 20 generations (if not extinct). Selection against deleterious mutations was allowed to occur within lines only, between lines or equal within and between lines, and surviving lines were either not crossed or crossed following every one or three generations of full-sib mating. The effectiveness of purging was indicated by the decreased number of lethal equivalents and the increased fitness of the purged population formed from crossing surviving lines after 20 generations under a given breeding scheme. The results show that the effectiveness of purging, the survival of the inbred lines and the inbreeding level attained are generally highest with between-line selection and lowest with within-line selection. Compared with no crossing, line crossing could lower the risk of extinction and the inbreeding coefficient of the purged population substantially with little loss of the effectiveness of purging. Compromising between the effectiveness of purging, and the risk of extinction and inbreeding coefficient, the breeding scheme with equal within- and between-line selection and crossing alternatively with full-sib mating is generally the most desirable scheme for purging deleterious mutations. Unless most deleterious mutations have relatively large effects on fitness in species with reproductive ability high enough to cope with the depressed fitness and thus increased risk of extinction with inbreeding, it is not justified to apply a breeding programme aimed at purging inbreeding depression by inbreeding and selection to a population of conservation concern.

Alleles↗
PubMed2006

Phylogeography and population structure of thornback rays (Raja clavata L., Rajidae).

The phylogeography of thornback rays (Raja clavata) was assessed from European waters, using five nuclear microsatellite loci and mitochondrial cytochome b sequences. Strong regional differentiation was found between the Mediterranean basin, the Azores and the European continental shelf. Allelic and haplotype diversities were high in Portuguese populations, consistent with the existence of a refugium along the Iberian Peninsula. Unexpectedly, high diversity was also found in the English Channel/North Sea area. The lowest genetic diversity was found in the Black Sea. Populations sampled from the Mediterranean, Adriatic and Black Seas were characterized by a single mitochondrial haplotype. This haplotype was also the most ancestral and widespread outside of the Mediterranean basin except for the Azores. Populations from the Azores were dominated by a second ancestral haplotype which was shared with British populations. Results from multidimensional scaling, amova and nested clade analysis indicate that British waters are a secondary contact zone recolonized from at least two refugia--one around the Iberian Peninsula and one possibly in the Azores. Links to a potential refugium known as the Hurd Deep, between Cornwall and Brittany, are discussed. Finally, a historical demographic analysis indicates that thornback ray populations started to expand between 580,000 and 362,000 years ago, which suggests that the Last Glacial Maximum (20,000 years ago) had mainly affected the distribution of populations rather than population size.

Animals↗