Genetic variation and population differentiation in species of Simocephalus (Cladocera, Daphniidae)

1986 ◽  
Vol 64 (10) ◽  
pp. 2246-2256 ◽  
Author(s):  
B. J. Hann ◽  
P. D. N. Hebert
Keyword(s):  
Genetic Variation ◽  
North America ◽  
Littoral Zone ◽  
Spatial Differentiation ◽  
Species Level ◽  
Evolutionary Divergence ◽  
Founder Effects ◽  
Allelic Substitution ◽  
The Mean ◽  
Low Levels

Microgeographic analysis of enzyme genetic variation in populations in the littoral zone cladoceran Simocephalus in southwestern Ontario has disclosed very low levels of intrapopulation variability. The mean percentage of polymorphic loci per population was 10.5%, and individual heterozygosity averaged less than 5% over all populations. Population structure typifies that of randomly mating, outbred sexual species. Most populations were polyclonal, with a few common widespread clones and several rarer ones, often found in only one pond. There were no significant temporal patterns in genotypic frequencies, but spatial differentiation of populations suggested that both selection and founder effects have played roles in the evolutionary divergence of these cyclic parthenogens. Despite extremely low intrapopulation and moderate intraspecific variation, there was extensive differentiation between species. As a consequence of virtually complete allelic substitution at several loci and great similarity or identity of alleles at others, diagnostic loci were detected in three of the four species. Of the four distinct clusters of populations, differentiated at the species level, three represented species previously recognized in North America (S. cf. vetulus, S. cf. serrulatus, S. cf. exspinosus), and the fourth group was identified as S. cf. congener, related to a taxon occurring in Europe, but not reported from North America. The great amount of divergence between populations of S. cf. exspinosus suggests that a complex of at least two sibling species exists within this taxon.

scholarly journals Genetic studies revealed differences between European and North American populations of Calypogeia azurea

2016 ◽  
Vol 42 (1) ◽  
pp. 19-26 ◽  
Author(s):  
Katarzyna Buczkowska ◽  
Alina Bączkiewicz ◽  
Patrycja Gonera
Keyword(s):  
Genetic Variation ◽  
North America ◽  
Genetic Distance ◽  
Gene Diversity ◽  
Oil Bodies ◽  
Genetic Studies ◽  
Isozyme Loci ◽  
The Mean ◽  
Different Parts ◽  
Nei's Genetic Distance

Abstract Calypogeia azurea, a widespread, subboreal-montane liverwort species, is one of a few representatives of the Calypogeia genus that are characterized by the occurrence of blue oil bodies. The aim of the study was to investigate the genetic variation and population structure of C. azurea originating from different parts of its distribution range (Europe and North America). Plants of C. azurea were compared with C. peruviana, another Calypogeia species with blue oil bodies. In general, 339 gametophytes from 15 populations of C. azurea were examined. Total gene diversity (HT) estimated on the basis of nine isozyme loci of C. azurea at the species level was 0.201. The mean Nei’s genetic distance between European populations was equal to 0.083, whereas the mean genetic distance between populations originating from Europe and North America was 0.413. The analysis of molecular variance (AMOVA) showed that 69% of C. azurea genetic variation was distributed among regions (Europe and North America), 15% - among populations within regions, and 16% - within populations. Our study revealed that C. azurea showed genetic diversity within its geographic distribution. All examined samples classified as C. azurea differed in respect of isozyme patterns from C. peruviana.

scholarly journals Genetic evaluation of seeds of highly endangered Pinus uliginosa Neumann from Węgliniec reserve for ex-situ conservation program

2011 ◽  
Vol 74 (3) ◽  
pp. 237-242 ◽  
Author(s):  
Andrzej Lewandowski ◽  
Jarosław Burczyk ◽  
Witold Wachowiak ◽  
Adam Boratyński ◽  
Wiesław Prus-Głowacki
Keyword(s):  
Genetic Variation ◽  
Genetic Erosion ◽  
Minimum Variance ◽  
Ex Situ ◽  
The Mean ◽  
Low Levels ◽  
Species Specific ◽  
High Level ◽  
Individual Trees ◽  
Pinus Uliginosa

Peat-bog pine <em>Pinus uliginosa</em> Neumann has become extinct or rare in many parts of Europe. We have investigated the levels of genetic variation and inbreeding in seeds collected from a highly endangered reserve of this species in Poland, using allozymes as genetic markers. Generally, a high level of genetic variation was observed. The mean expected heterozygosity was 0.376, while average (Na) and effective (Ne) numbers of alleles per locus were 2.45 and 1.67, respectively. Nevertheless, we have detected relatively low levels of outcrossing, and potential biparental inbreeding. The population-wide multilocus outcrossing rate was estimated to be 0.706 (±0.091), while the minimum variance mean of single-locus estimates was distinctly lower (ts=0.611). The estimates of outcrossing calculated for individual trees ranged widely from 0.051 to 1.017, indicating the complexity of outcrossing patterns. The investigated population of <em>P. uliginasa</em> from Węgliniec is small and surrounded by extensive forest stands of <em>P. sylvestris</em>. Our three-year records of phenological observations demonstrated that flowering periods for <em>P. uliginosa</em> and <em>P. sylvestris</em> overlap, allowing for cross-pollination. The possibility of <em>P. uliginosa</em> pollination by <em>P. sylvestris</em> creates a potential danger of genetic erosion of the <em>P. uliginosa</em> gene pool. Nonetheless, based on a species specific cpDNA marker we have found that among 533 seedlings of <em>P. uliginosa</em> there were only six seedlings carrying cpDNA marker specific for <em>P. sylvestris</em>, indicating that such hybridization seems to be rare.

scholarly journals RE-INTERPRETATION OF GENETIC VARIATION IN SIMOCEPHALUS (CLADOCERA, DAPHNIIDAE)

Genetics ◽  
1982 ◽  
Vol 102 (1) ◽  
pp. 101-107
Author(s):  
B J Hann ◽  
P D N Hebert
Keyword(s):  
Genetic Variation ◽  
Sharp Contrast ◽  
Genetic Identity ◽  
Enzyme Loci ◽  
Allelic Substitution ◽  
Low Levels

ABSTRACT Populations of several co-existing species of Simocephalus were examined electrophoretically at 11 enzyme loci. The prevailing pattern was one of extensive allelic substitution between species and low levels of polymorphism (0-10%) within species. Genetic identity values between species were very low (10-50%). These results concur with those for other cyclic parthenogens, but are in sharp contrast to previous interpretation of data derived from populations of Simocephalus from the same sites.

Population Genetics ofCaenorhabditis elegans: The Paradox of Low Polymorphism in a Widespread Species

Genetics ◽  
2003 ◽  
Vol 163 (1) ◽  
pp. 147-157 ◽  
Author(s):  
Arjun Sivasundar ◽  
Jody Hey
Keyword(s):  
Genetic Variation ◽  
Microsatellite Loci ◽  
Population Expansion ◽  
Widespread Species ◽  
C Elegans ◽  
Model Research ◽  
The World ◽  
Natural Isolates ◽  
History Of ◽  
Low Levels

AbstractCaenorhabditis elegans has become one of the most widely used model research organisms, yet we have little information on evolutionary processes and recent evolutionary history of this widespread species. We examined patterns of variation at 20 microsatellite loci in a sample of 23 natural isolates of C. elegans from various parts of the world. One-half of the loci were monomorphic among all strains, and overall genetic variation at microsatellite loci was low, relative to most other species. Some population structure was detected, but there was no association between the genetic and geographic distances among different natural isolates. Thus, despite the nearly worldwide occurrence of C. elegans, little evidence was found for local adaptation in strains derived from different parts of the world. The low levels of genetic variation within and among populations suggest that recent colonization and population expansion might have occurred. However, the patterns of variation are not consistent with population expansion. A possible explanation for the observed patterns is the action of background selection to reduce polymorphism, coupled with ongoing gene flow among populations worldwide.

scholarly journals Characterization of Deleterious Mutations in Outcrossing Populations

Genetics ◽  
1998 ◽  
Vol 150 (2) ◽  
pp. 945-956 ◽  
Author(s):  
Hong-Wen Deng
Keyword(s):  
Genetic Variation ◽  
Genetic Variance ◽  
Estimation Bias ◽  
Deleterious Mutations ◽  
Environmental Variance ◽  
Higher Power ◽  
Sib Mating ◽  
The Mean ◽  
Simulation Results

Abstract Deng and Lynch recently proposed estimating the rate and effects of deleterious genomic mutations from changes in the mean and genetic variance of fitness upon selfing/outcrossing in outcrossing/highly selfing populations. The utility of our original estimation approach is limited in outcrossing populations, since selfing may not always be feasible. Here we extend the approach to any form of inbreeding in outcrossing populations. By simulations, the statistical properties of the estimation under a common form of inbreeding (sib mating) are investigated under a range of biologically plausible situations. The efficiencies of different degrees of inbreeding and two different experimental designs of estimation are also investigated. We found that estimation using the total genetic variation in the inbred generation is generally more efficient than employing the genetic variation among the mean of inbred families, and that higher degree of inbreeding employed in experiments yields higher power for estimation. The simulation results of the magnitude and direction of estimation bias under variable or epistatic mutation effects may provide a basis for accurate inferences of deleterious mutations. Simulations accounting for environmental variance of fitness suggest that, under full-sib mating, our extension can achieve reasonably well an estimation with sample sizes of only ∼2000-3000.

Pattern of plasma progesterone, oestradiol-17β, luteinizing hormone and androgen in non-pregnant buffalo (Bubalus bubalis)

1982 ◽  
Vol 100 (2) ◽  
pp. 279-284 ◽  
Author(s):  
R. C. Arora ◽  
R. S. Pandey
Keyword(s):  
Luteinizing Hormone ◽  
Peak Level ◽  
Systemic Circulation ◽  
Bubalus Bubalis ◽  
High Concentration ◽  
Plasma Progesterone ◽  
Blood Samples ◽  
Androgen Level ◽  
The Mean ◽  
Low Levels

Abstract. Domestic buffaloes were used to characterize the pattern of progesterone, oestradiol-17β, LH and androgen in the systemic circulation following infertile insemination. Concentrations of hormones were measured by RIA in blood samples collected daily or at alternate days following insemination. The concentration of progesterone was lowest on the day of insemination, and increased significantly to a peak level of 4.00 ± 0.60 ng/ml by day 13 post insemination. After day 17, it declined significantly (P < 0.01) to reach low levels by day 21. The concentration of oestradiol-17β was high at the time of insemination and declined significantly (P < 0.01) by day 2 after insemination. It was maintained around the basal level till day 18 with minor peaks in between this period. It again rose significantly (P < 0.01) at subsequent oestrus. The mean level of LH was highest at the time of insemination, and declined significantly (P < 0.01) by day 1 post insemination. It did not vary appreciably till the animal returned to oestrus. The oestrous value of LH and progesterone were negatively correlated (r = −0.77). The androgen level was observed to be high at insemination in 3 out of 5 animals, but the overall pattern of this steroid was inconsistent during the period studied. A high concentration of androgen was recorded in all the animals from day 2–5 before the onset of oestrus.

PREDATION BY INSECTS AND SPIDERS INHABITING COLONIAL WEBS OF HYPHANTRIA CUNEA

1972 ◽  
Vol 104 (8) ◽  
pp. 1197-1207 ◽  
Author(s):  
R. F. Morris
Keyword(s):  
Population Dynamics ◽  
Nova Scotia ◽  
North America ◽  
Population Density ◽  
New Brunswick ◽  
Numerical Response ◽  
Initial Number ◽  
Hyphantria Cunea ◽  
The North ◽  
The Mean

AbstractThe number of predators inhabiting nests of Hyphantria cunea Drury was recorded annually for 13 years in four areas in New Brunswick and two areas on the coast of Nova Scotia. The most common groups were the pentatomids and spiders, which sometimes reproduced within the nests, but the mean number per nest was low in relation to the number of H. cunea larvae in the colonies. The rate of predation on fifth-instar larvae was low. Small or timid predators appeared to prey largely on moribund larvae or small saprophagans during the principal defoliating instars of H. cunea.No relationship could be detected between the number of larvae reaching the fifth instar and the number of predators in the colony; nor could any functional or numerical response of the predators to either the initial number of larvae per colony or the population density of colonies be found. It is concluded that the influence of the nest-inhabiting predators is small and relatively stable, and may be treated as a constant in the development of models to explain the population dynamics of H. cunea.H. cunea is a pest in parts of Europe and Asia, where it has been accidentally introduced from North America. The introduction to other continents of the North American predator, Podisus maculiventiis (Say), is discussed briefly.

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