scholarly journals The chiasmata systems of Scottish Chysolina latecincta (Demaison, 1896) (Coleoptera, Chrysomelidae)

2021 ◽  
Vol 15 (4) ◽  
pp. 339-343
Author(s):  
Eduard Petitpierre
Keyword(s):  
Genetic Recombination ◽  
Selective Advantage ◽  
Shetland Islands ◽  
The Mean ◽  
Geographic Sources

The meiotic systems of some Scottish individuals of the rare Chrysolina latecincta ssp. intermedia (Franz, 1938) have been analyzed from meiotic cells at diakinesis to study the types of chromosomal bivalents and the number and locations of their chiasmata. The mean number of unichiasmate was about two-thirds and that of bichiasmate bivalents about one-third. Most chiasmata were at distal positions and there were no pairwise statistically significant differences in the mean number of chiasmata and those of unichiasmate and bichiasmate bivalents between the three surveyed geographic sources of these Scottish individuals. However, pairwise significant differences were found in the mean number of proximal + interstitial chiasmata between Loch Etive (Argyllshire) and both Orkney and Shetland Islands individuals. The presumed higher values of genetic recombination due to the proximal + interstitial chiasmata with regard to the prevailing distal ones, might provide a slight selective advantage to the insular individuals against the more extreme climates of both islands compared with the Loch Etive site.

scholarly journals The differential transmissibility of myxoma virus strains of differing virulence grades by the rabbit flea Spilopsyllus cuniculi (Dale)

1975 ◽  
Vol 75 (2) ◽  
pp. 237-247 ◽  
Author(s):  
A. R. Mead-Briggs ◽  
J. A. Vaughan
Keyword(s):  
Host Resistance ◽  
Oryctolagus Cuniculus ◽  
Selective Advantage ◽  
Myxoma Virus ◽  
Laboratory Studies ◽  
Natural Conditions ◽  
Male And Female ◽  
The Mean ◽  
Virus Strains ◽  
Sampling Times

SUMMARYLaboratory studies showed that few rabbit fleas (Spilopsyllus cuniculi (Dale)) transmitted myxomatosis after removal from wild rabbits (Oryctolagus cuniculus (L)) that had been infected for fewer than 10–12 days, irrespective of the virulence of the myxoma virus strain involved. Rabbits infected with fully virulent (Grade I) strains died within 10–15 days and few fleas from these hosts became infective; averaging all the samples taken, 12% of the fleas were infective. Also, few fleas acquired infectivity on individual rabbits which recovered from infection with attenuated strains; the mean was 8% infective. Rabbits which died between 17 and 44 days after infection had higher proportions of infective fleas at all sampling times; the mean was 42% infective. Male and female fleas transmitted virus with equal efficiency.For rabbits infected with any of the attenuated virus strains the mean percentage of infective fleas was inversely related to the survival time of the host. Rabbits infected with moderately attenuated strains (Grades IIIA and IIIB) had, on average, the highest proportion of infective fleas; hence such strains have a selective advantage and have become predominant under natural conditions in Britain. The changes that might occur if there is an increase in host resistance to myxomatosis are discussed.

Survey of Postharvest-Processed Oysters in the United States for Levels of Vibrio vulnificus and Vibrio parahaemolyticus

2009 ◽  
Vol 72 (10) ◽  
pp. 2110-2113 ◽  
Author(s):  
ANGELO DePAOLA ◽  
JESSICA L. JONES ◽  
KATHY E. NOE ◽  
ROBIN H. BYARS ◽  
JOHN C. BOWERS
Keyword(s):  
Vibrio Vulnificus ◽  
Gulf Coast ◽  
Virulence Gene ◽  
Selective Advantage ◽  
The United States ◽  
Most Probable Number ◽  
Probable Number ◽  
Mild Heat ◽  
Thermostable Direct Hemolysin ◽  
The Mean

From June through October 2004, the U.S. Food and Drug Administration collected oysters (61 samples) that had been subjected to postharvest processing (PHP) methods, including mild heat treatment, freezing, and high hydrostatic pressure, from processors and retail markets in various states to determine Vibrio vulnificus and V. parahaemolyticus levels. Presence in a 25-g sample and most probable number (MPN) using standard enrichment and selective isolation procedures were utilized. Suspect colonies were isolated and identified using DNA probe colony hybridization. Neither species of vibrio was detected in 25-g portions of most samples regardless of the PHP. The lowest frequency of isolation of either pathogen (<10%) was observed with the mild heat process. Few (12 to 13%) frozen samples collected at the processor but not at retail contained >30 MPN/g of either pathogen. The mean levels of either organism in PHP oysters observed in the present study were 5 to 6 log less than in unprocessed raw Gulf Coast oysters. Of the 70 V. vulnificus isolates examined, only 5 possessed the putative virulence marker, type B 16S rRNA. Neither the thermostable direct hemolysin (tdh) nor the tdh-related hemolysin (trh) virulence gene was detected in any of the 40 V. parahaemolyticus isolates examined in the present study. These data suggest that if there is any selective advantage to pathogenic strains of V. vulnificus and V. parahaemolyticus, these differences are minimal. These results indicate that all PHP treatments greatly reduce exposure of V. vulnificus and V. parahaemolyticus to raw-oyster consumers. Consequently, these PHP oysters pose a much lower risk of illness to consumers due to these pathogens.

New data on the occurrence of Acanthocephala in some fish in Admiralty Bay (South Shetland Islands)

2013 ◽  
Vol 58 (4) ◽  
Author(s):  
Krzysztof Zdzitowiecki ◽  
Zdzisław Laskowski
Keyword(s):  
South Shetland Islands ◽  
Admiralty Bay ◽  
Shetland Islands ◽  
Notothenia Coriiceps ◽  
Reverse Situation ◽  
The Mean ◽  
Trematomus Bernacchii ◽  
Notothenia Rossii

AbstractNew data on the infection with Acanthocephala of 33 fish caught in Admiralty Bay in November 2007 to January 2008 are given. These fish belong to 5 species: Notothenia rossii (22 immature specimens), Lindbergichthys nudifrons (n = 7), Trematomus bernacchii (n = 1), T. newnesi (n = 1) and Harpagifer antarcticus (n = 2). Three species of Echinorhynchida: Aspersentis megarhynchus, Metacanthocephalus dalmori and M. johnstoni and four species of Polymorphida: Corynosoma arctocephali, C. bullosum, C. hamanni and C. pseudohamanni, were found. Prevalence of N. rossii and L. nudifrons was 100%. The mean abundance of infection of N. rossii (125.09) was larger than that of Notothenia coriiceps (82.93). Data of infection of N. rossii in 2007 was almost identical with that in 1979 (mean abundance 118.66). The most abundant in this host were A. megarhynchus, M. johnstoni, C. hamanni and C. pseudohamanni (mean abundances 36.36, 29.77, 13.86 and 44.73, respectively). In total Echinorhynchida were more abundant than Polymorphida in 2007/08 (66.18 versus 58.91). Reverse situation was in 1979 (mean abundance 47.36 for Echinorhynchida and 71.3 for Polymorphida. Only 7 L. nudifrons were examined in 2007/08 and Echinorhynchida were more numerous in this host (mean abundance 26.71) than Polymorphida (10.29). Single specimens of other fish were infected with a few Acanthocephala belonging to species recorded in the same hosts with those found in 1978/79.

scholarly journals Haplotype block dynamics in hybrid populations

2016 ◽  
Author(s):  
Thijs Janzen ◽  
Arne W. Nolte ◽  
Arne Traulsen
Keyword(s):  
Relative Frequency ◽  
Haplotype Block ◽  
Genetic Recombination ◽  
Universal Function ◽  
Analytical Treatment ◽  
Ancestral Species ◽  
Haplotype Blocks ◽  
Hybrid Genome ◽  
The Mean ◽  
Over Time

ABSTRACTWhen species originate through hybridization, the genomes of the ancestral species are blended together. Over time genomic blocks that originate from either one of the ancestral species accumulate in the hybrid genome through genetic recombination. Modeling the accumulation of ancestry blocks can elucidate processes and patterns of genomic admixture. However, previous models have ignored ancestry block dynamics for chromosomes that consist of a discrete, finite number of chromosomal elements. Here we present an analytical treatment of the dynamics of the mean number of blocks over time, for continuous and discrete chromosomes, in finite and infinite populations. We describe the mean number of haplotype blocks as a universal function dependent on population size, the number of genomic elements per chromosome, the number of recombination events, and the initial relative frequency of the ancestral species.

scholarly journals Prediction of rates of inbreeding in selected populations

1990 ◽  
Vol 55 (1) ◽  
pp. 41-54 ◽  
Author(s):  
Naomi R. Wray ◽  
Robin Thompson
Keyword(s):  
Selective Advantage ◽  
Mass Selection ◽  
Effective Population ◽  
The Matrix ◽  
Mean And Variance ◽  
Unselected Population ◽  
The Mean ◽  
Number Of Individuals ◽  
The Relationship

SummaryA method is presented for the prediction of rate of inbreeding for populations with discrete generations. The matrix of Wright's numerator relationships is partitioned into ‘contribution’ matrices which describe the contribution of the Mendelian sampling of genes of ancestors in a given generation to the relationship between individuals in later generations. These contributions stabilize with time and the value to which they stabilize is shown to be related to the asymptotic rate of inbreeding and therefore also the effective population size, where N is the number of individuals per generation and μr and are the mean and variance of long-term relationships or long-term contributions. These stabilized values are then predicted using a recursive equation via the concept of selective advantage for populations with hierarchical mating structures undergoing mass selection. Account is taken of the change in genetic parameters as a consequence of selection and also the increasing ‘competitiveness’ of contemporaries as selection proceeds. Examples are given and predicted rates of inbreeding are compared to those calculated in simulations. For populations of 20 males and 20, 40, 100 or 200 females the rate of inbreeding was found to increase by as much as 75% over the rate of inbreeding in an unselected population depending on mating ratio, selection intensity and heritability of the selected trait. The prediction presented here estimated the rate of inbreeding usually within 5% of that calculated from simulation.

MARKER-DEPENDENT RECOMBINATION IN T4 BACTERIOPHAGE. II. THE EVALUATION OF MISMATCH REPAIRABILITIES IN CROSSES WITHIN INDICATOR DISTANCES

Genetics ◽  
1982 ◽  
Vol 102 (4) ◽  
pp. 627-637
Author(s):  
V P Shcherbakov ◽  
L A Plugina ◽  
E A Kudryashova ◽  
O I Efremova ◽  
S T Sizova ◽  
...  
Keyword(s):  
Mismatch Repair ◽  
Genetic Recombination ◽  
Double Exchange ◽  
Quantitative Agreement ◽  
Base Sequence ◽  
Repair Mechanism ◽  
T4 Bacteriophage ◽  
T4 Phage ◽  
The Mean ◽  
Three Factor

ABSTRACT The contribution of mismatch repair to genetic recombination in T4 phage has been evaluated by three independent approaches: (1) testing for non-additivity of recombinant frequencies; (2) measurements of double exchange frequencies in three-factor crosses: (3) comparisons of recombination abilities of mutations occupying the same site. Quantitative agreement among the results of these approaches suggests that within distances much less than the mean length of hybrid regions, mismatch repair accounts perfectly for high negative interference as measured in three-factor crosses and as manifested by non-additivity in two-factor crosses. The mismatch repair mechanism readily recognizes only particular mismatches, the repair frequency being dependent on the base sequence in both strands of the mismatched region.

scholarly journals Intraclutch Egg-Size Variation in Magellanic Penguins

The Condor ◽  
2005 ◽  
Vol 107 (4) ◽  
pp. 921-926
Author(s):  
Nicole E. Rafferty ◽  
P. Dee Boersma ◽  
Ginger A. Rebstock
Keyword(s):  
Egg Size ◽  
Size Variation ◽  
Selective Advantage ◽  
Chick Survival ◽  
Female Age ◽  
Spheniscus Magellanicus ◽  
Fledging Success ◽  
Magellanic Penguins ◽  
The Mean ◽  
Oceanographic Conditions

Abstract We investigated patterns and consequences of intraclutch egg-size variation in Magellanic Penguins (Spheniscus magellanicus). First-laid eggs were significantly larger than second-laid eggs, although the mean difference represented only 2% of an average egg's volume. The degree of intraclutch egg-size variation was similar among years and females of different ages. Intraclutch egg-size variation did not affect intraclutch differences in chick hatching weights or fledging success. We found no selective advantage for laying eggs of different sizes. Because both eggs have an equal probability of being lost, chance favors equal provisioning of eggs. Egg volume explained 35% of the variation in hatching weight but did not determine fledging success. Laying order, year, and female age were better predictors of fledging success than egg size. Factors such as laying and hatching order, parental quality, oceanographic conditions, fights, and predation are more important in determining chick survival than are differences in egg size.

scholarly journals Warfarin resistance: a balanced polymorphism in the Norway rat

1977 ◽  
Vol 30 (3) ◽  
pp. 257-263 ◽  
Author(s):  
J. H. Greaves ◽  
R. Redfern ◽  
P. B. Ayres ◽  
J. E. Gill
Keyword(s):  
Ecological Factors ◽  
Selective Advantage ◽  
Relative Fitness ◽  
High Susceptibility ◽  
Norway Rat ◽  
Anticoagulant Rodenticides ◽  
Balanced Polymorphism ◽  
Monogenic Resistance ◽  
The Mean ◽  
Warfarin Resistance

SUMMARYThe frequency of monogenic resistance to anticoagulant rodenticides in Rattus norvegicus in an area straddling the England–Wales border was monitored from 1967 until 1975. Rats were trapped on farms and tested in the laboratory by administering a dose of warfarin lethal to susceptibles. The mean incidence of resistance was 44% and did not change significantly, despite the extensive use of anticoagulants by farmers during the 9-year period. In 1975 more refined techniques showed that the frequencies of susceptible (SS) and resistant (RR) homozygotes were significantly below the Hardy–Weinberg expectations and simple estimates of the relative fitness ratios for the RR, RS and SS phenotypes were 0·37, 1·0 and 0·68 respectively. In two relatively isolated valleys, where selection with anticoagulants was minimal, the frequency of resistance decreased significantly from 57% to 39% during 1973–5. The results are consistent with the hypothesis that a balanced polymorphism is being maintained. Selection against susceptible homozygotes by the use of anticoagulant rodenticides, and against the resistant homozygote due to its high susceptibility to a primary deficiency of vitamin K gives the heterozygotes a selective advantage. A number of ecological factors that influence the incidence of the resistance are discussed briefly.

scholarly journals THE EVOLUTION OF SELF-REGULATED TRANSPOSITION OF TRANSPOSABLE ELEMENTS

Genetics ◽  
1986 ◽  
Vol 112 (2) ◽  
pp. 359-383
Author(s):  
B Charlesworth ◽  
C H Langley
Keyword(s):  
Transposable Elements ◽  
High Frequency ◽  
Germ Line ◽  
Genetic Recombination ◽  
Somatic Cells ◽  
Selective Advantage ◽  
Selective Force ◽  
Cis Acting ◽  
Bacterial Plasmids ◽  
Regulatory Effects

ABSTRACT This paper examines the conditions under which self-regulated rates of transposition can evolve in populations of transposable elements infecting sexually reproducing hosts. Models of the evolution of both cis-acting regulation (transposition immunity) and trans-acting regulation (transposition repression) are analyzed. The potential selective advantage to regulation is assumed to be derived from the deleterious effects of mutations associated with the insertion of newly replicated elements. It is shown that both types of regulation can easily evolve in hosts with low rates of genetic recombination per generation, such as bacteria or bacterial plasmids. Conditions are much more restrictive in organisms with relatively free recombination. In haploids, the main selective force promoting regulation is the induction of lethal or sterile mutations by transposition; in diploids, a sufficiently high frequency of dominant lethal or sterile mutations associated with transpositions is required. Data from Drosophila and maize suggest that this requirement can sometimes be met. Coupling of regulatory effects across different families of elements would also aid the evolution of regulation. The selective advantages of restricting transposition to the germ line and of excising elements from somatic cells are discussed.

scholarly journals Glaciological studies on the King George Island ice cap, South Shetland Islands, Antarctica

1998 ◽  
Vol 27 ◽  
pp. 105-109 ◽  
Author(s):  
Wen Jiahong ◽  
Kang Jiancheng ◽  
Han Jiankang ◽  
Xie Zichu ◽  
Liu Leibao ◽  
...  
Keyword(s):  
Accumulation Rate ◽  
Stable State ◽  
Equilibrium Line ◽  
South Shetland Islands ◽  
Mean Annual Temperature ◽  
King George Island ◽  
Equilibrium Line Altitude ◽  
Shetland Islands ◽  
Ice Cap ◽  
The Mean

The King George Island ice cap, South Shetland Islands, Antarctica, was studied between 1985 and 1992. At the steady-state equilibrium-line altitude of the ice cap, the mean annual temperature is -3.6°C, the mean summer (December-February) temperature is 0°C and annual precipitation is 800 mm w.e. Precipitation increases rapidly with elevation, and annual accumulation rate at the Main Dome summit reaches 2480 mm a−1. Between 1985 and 1991 the equilibrium-line elevation averaged 140-150 m a.s.l. The ice cap has been in an overall stable state for the past 20 years, going from a weak negative to a small positive mass imbalance as increased precipitation outweighs the effects of rising temperatures. Temperatures at the bottom of the active layer over most of the accumulation area are close to 0°C, with colder temperatures down to -1.9°C in the ablation zone. Soluble impurities in the ice cap are mainly from marine sources, while undissolved mineral material amounts to only 15-54% of the total microparticle content.

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