Estimating population variability of aphids (Hemiptera: Aphididae): how many years are required?

2016 ◽  
Vol 149 (1) ◽  
pp. 48-55 ◽  
Author(s):  
Robert J. Lamb ◽  
Patricia A. MacKay ◽  
Andrei Alyokhin
Keyword(s):  
Time Series ◽  
Population Dynamics ◽  
Standard Deviation ◽  
Coefficient Of Variation ◽  
Population Variability ◽  
The Other ◽  
Macrosiphum Euphorbiae ◽  
Mean Values ◽  
Robust Estimates ◽  
Aphis Nasturtii

AbstractVariability is an important characteristic of population dynamics, but the length of the time series required to estimate population variability is poorly understood. To this end, population variability of Macrosiphum euphorbiae (Thomas), Myzus persicae (Sulzer), and Aphis nasturtii (Kaltenbach) (Hemiptera: Aphididae) was investigated. Population variability (measured as PV, a proportion between 0 and 1) was estimated for time series of 3–62 years, giving replicate estimates for time series of 3–20 years that were normally distributed. Mean values for PV were more uniform for a time series of 12 years or longer than for shorter ones. The standard deviation of PV declined to a minimum at 12–15 years, as the length of the time series increased. Discrimination of estimates of PV was reliable for 15-year time series and longer, but not necessarily for shorter ones. Although M. euphorbiae had a relatively low PV, the coefficient of variation of that PV (12.5), was higher than for the other two species (3.5, 4.5). For robust estimates of PV, a time series of 15 years is recommended, because it minimises the standard deviation of PV, and discriminates values of PV that differ by 0.06 on a 0–1 scale.

scholarly journals A Comparison of Three Gap Filling Techniques for Eddy Covariance Net Carbon Fluxes in Short Vegetation Ecosystems

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Xiaosong Zhao ◽  
Yao Huang
Keyword(s):  
Time Series ◽  
Standard Deviation ◽  
Diurnal Variation ◽  
Eddy Covariance ◽  
Nonlinear Regression ◽  
Missing Values ◽  
The Other ◽  
Gap Filling ◽  
Benchmark Datasets ◽  
Filling Method

Missing data is an inevitable problem when measuring CO2, water, and energy fluxes between biosphere and atmosphere by eddy covariance systems. To find the optimum gap-filling method for short vegetations, we review three-methods mean diurnal variation (MDV), look-up tables (LUT), and nonlinear regression (NLR) for estimating missing values of net ecosystem CO2exchange (NEE) in eddy covariance time series and evaluate their performance for different artificial gap scenarios based on benchmark datasets from marsh and cropland sites in China. The cumulative errors for three methods have no consistent bias trends, which ranged between −30 and +30 mgCO2 m−2from May to October at three sites. To reduce sum bias in maximum, combined gap-filling methods were selected for short vegetation. The NLR or LUT method was selected after plant rapidly increasing in spring and before the end of plant growing, and MDV method was used to the other stage. The sum relative error (SRE) of optimum method ranged between −2 and +4% for four-gap level at three sites, except for 55% gaps at soybean site, which also obviously reduced standard deviation of error.

Population variability and persistence of three aphid pests of potatoes over 60 years

2011 ◽  
Vol 143 (1) ◽  
pp. 91-101 ◽  
Author(s):  
Robert J. Lamb ◽  
Patricia A. MacKay ◽  
Andrei Alyokhin
Keyword(s):  
Native Species ◽  
Potato Crop ◽  
Natural Populations ◽  
Sampling Interval ◽  
Aphid Species ◽  
Population Variability ◽  
Macrosiphum Euphorbiae ◽  
Aphis Nasturtii ◽  
Species Specific ◽  
Interspecific Comparisons

AbstractAbundance, persistence, and variability of populations of Macrosiphum euphorbiae (Thomas), Myzus persicae (Sulzer), and Aphis nasturtii Kaltenbach (Hemiptera: Aphididae) in potato plots for intervals of 58 years (n = 1), 29 years (n = 2), 19–20 years (n = 3), and 9–10 years (n = 6) were compared. The abundance of M. euphorbiae showed no trend among decades and varied 2.4-fold, whereas that of M. persicae and A. nasturtii declined and showed 54-fold and 3700-fold variation, respectively. All three aphid species persisted through the first five decades and M. euphorbiae also persisted through the sixth (last) decade, but M. persicae and A. nasturtii failed to persist for 1 and 3 years of the last decade, respectively. Population variability (a proportion between 0 and 1) measured over a 58-year interval was high: 0.585 for M. euphorbiae, 0.771 for M. persicae, and 0.830 for A. nasturtii. During the first three but not the last three decades, population variability increased with sampling interval, owing to dramatic declines in abundance for M. persicae and A. nasturtii and one stable decade for M. euphorbiae, but no evidence of a more-time — more-variation effect was detected. Persistence was not related to population variability, but declined with abundance. Populations did not reach equilibrium, because of declining abundance for M. persicae and A. nasturtii and changes in population variability from decade to decade for M. euphorbiae. Populations of M. persicae and A. nasturtii from this crop monoculture were less stable than previously studied natural populations of a native aphid species. In contrast, the population of M. euphorbiae, a native species, had variability in a potato crop similar to that of the previously studied native species. The high population variability of M. persicae and A. nasturtii may be associated with their status as introduced species. The dynamic and species-specific characteristics of population variability require that interspecific comparisons be considered cautiously.

scholarly journals O efeito da padronização das notas sobre os resultados da avaliação dos cursos de Engenharia Civil

2018 ◽  
Vol 1 (39) ◽  
pp. 54
Author(s):  
Julio Gomes
Keyword(s):  
Standard Deviation ◽  
Theoretical Analysis ◽  
Coefficient Of Variation ◽  
Relative Frequency ◽  
Civil Engineering ◽  
The Other ◽  
Low Correlation ◽  
Standardization Procedure ◽  
Two Alternatives

This study aims to present an analysis of the effect of grade standardization on the results of the assessment of Civil Engineering undergraduate courses. The analyzed data came from the assessment carried out in the year 2014. Initially, it was performed a theoretical analysis of the equations that define the standardization procedure to assess the effect on mean, standard deviation and coefficient of variation of original grades. Following, it is presented a comparison between the statistics of original grades and standard grades to show the effect of different scale amplitudes of the evaluation components. It was also calculated the correlation among the variables used to define the course preliminary concept (CPC). The results showed low correlation between the variables Note and IDD and the other variables that are part of the CPC. Finally, we presented two alternatives to define scale ranges to the evaluation components, and compared the CPC values calculated from those two alternatives to the CPC values calculated from the current standardization procedure. The results showed that the current standardization procedure increased the relative frequency of both 2 and 3 concepts, and decreases the relative frequency of 4 concept compared to the two alternatives suggested.

Abundance and stability of populations of chewing lice (Phthiraptera: Amblycera and Ischnocera) infesting two species of woodpeckers (Aves: Piciformes: Picidae)

2018 ◽  
Vol 150 (2) ◽  
pp. 180-189 ◽  
Author(s):  
Robert J. Lamb ◽  
Terry D. Galloway
Keyword(s):  
Population Dynamics ◽  
Sex Ratio ◽  
Population Variability ◽  
The Other ◽  
Population Stability ◽  
Mean Intensity ◽  
Chewing Lice ◽  
The Mean ◽  
Louse Species ◽  
Colaptes Auratus

AbstractThe annual abundance of chewing lice (Phthiraptera) was recorded from 1996 to 2015 in Manitoba, Canada, on two species of woodpeckers (Piciformes: Picidae). Yellow-bellied sapsuckers (Sphyrapicus varius (Linnaeus)) were infested with Menacanthus pici (Denny) (Amblycera: Menoponidae) and Penenirmus auritus (Scopoli) (Ischnocera: Philopteridae); northern flickers (Colaptes auratus (Linnaeus)) were also infested with M. pici, as well as two other Ischnocera, Penenirmus jungens (Kellogg) and Picicola porisma Dalgleish. The mean annual abundance varied from nine to 51 lice per bird for the four species, with prevalence, mean intensity, sex ratio, and nymphs per female also varying among louse species. Menacanthus pici populations on both hosts were unstable: abundance rose over two decades because of increasing prevalence, whereas the abundance of the other three louse species fluctuated around a mean. Population variability was similar for the lice on both hosts, with the metric, PV, ranging from 0.41 to 0.51 on a 0–1 scale, once the effect of the trend in abundance for M. pici had been removed. Although the population dynamics for species of lice on these two woodpeckers were distinct, inter-specific differences in population stability were less pronounced than observed in the few other species of bird lice studied in this way.

Seasonal dynamics of three coexisting aphid species: implications for estimating population variability

2013 ◽  
Vol 145 (3) ◽  
pp. 283-291 ◽  
Author(s):  
Robert J. Lamb ◽  
Patricia A. MacKay ◽  
Andrei Alyokhin
Keyword(s):  
Life History ◽  
Early Stage ◽  
Aphid Species ◽  
Population Variability ◽  
Macrosiphum Euphorbiae ◽  
Seasonal Abundance ◽  
Seasonal Patterns ◽  
Annual Peak ◽  
Aphis Nasturtii ◽  
Peak Abundance

AbstractSeasonal patterns of abundance and population variability were determined for Macrosiphum euphorbiae (Thomas), Myzus persicae (Sulzer), and Aphis nasturtii (Kaltenbach) (Hemiptera: Aphididae) in potato plots from weekly samples for 28 years. All species showed a single annual peak, but arrived and reached peak abundance at different times. Population variability (PV, a proportion between 0 and 1) for the week of peak abundance was close to that of other sample weeks and mean seasonal abundance. Based on mid-season abundance, PV of 0.76 for M. persicae differed significantly from 0.80 for A. nasturtii, as well as from 0.59 for M. euphorbiae. A weekly time scale for abundance, initiated at an early stage of plant growth, produced slightly different estimates of PV early and late in the season than a scale centred on peak abundance for each species. PV at the time of invasion differed from estimates for the rest of the summer. The annual abundance used to estimate PV was best determined in the context of aphid life history. Nevertheless, PV provided a robust and precise metric for comparing population variability among the three species, regardless of their seasonal patterns of abundance.

scholarly journals Uncertainties Analysis of Collapse Susceptibility Prediction Based on Remote Sensing and GIS: Influences of Different Data-Based Models and Connections between Collapses and Environmental Factors

2020 ◽  
Vol 12 (24) ◽  
pp. 4134
Author(s):  
Wenbin Li ◽  
Xuanmei Fan ◽  
Faming Huang ◽  
Wei Chen ◽  
Haoyuan Hong ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Environmental Factors ◽  
Mean Value ◽  
Information Value ◽  
The Other ◽  
Weight Of Evidence ◽  
Coupled Models ◽  
Mean Values ◽  
Large Standard Deviation ◽  
Average Rank

To study the uncertainties of a collapse susceptibility prediction (CSP) under the coupled conditions of different data-based models and different connection methods between collapses and environmental factors, An’yuan County in China with 108 collapses is used as the study case, and 11 environmental factors are acquired by data analysis of Landsat TM 8 and high-resolution aerial images, using a hydrological and topographical spatial analysis of Digital Elevation Modeling in ArcGIS 10.2 software. Accordingly, 20 coupled conditions are proposed for CSP with five different connection methods (Probability Statistics (PSs), Frequency Ratio (FR), Information Value (IV), Index of Entropy (IOE) and Weight of Evidence (WOE)) and four data-based models (Analytic Hierarchy Process (AHP), Multiple Linear Regression (MLR), C5.0 Decision Tree (C5.0 DT) and Random Forest (RF)). Finally, the CSP uncertainties are assessed using the area under receiver operation curve (AUC), mean value, standard deviation and significance test, respectively. Results show that: (1) the WOE-based models have the highest AUC accuracy, lowest mean values and average rank, and a relatively large standard deviation; the mean values and average rank of all the FR-, IV- and IOE-based models are relatively large with low standard deviations; meanwhile, the AUC accuracies of FR-, IV- and IOE-based models are consistent but higher than those of the PS-based model. Hence, the WOE exhibits a greater spatial correlation performance than the other four methods. (2) Among all the data-based models, the RF model has the highest AUC accuracy, lowest mean value and mean rank, and a relatively large standard deviation. The CSP performance of the RF model is followed by the C5.0 DT, MLR and AHP models, respectively. (3) Under the coupled conditions, the WOE-RF model has the highest AUC accuracy, a relatively low mean value and average rank, and a high standard deviation. The PS-AHP model is opposite to the WOE-RF model. (4) In addition, the coupled models show slightly better CSP performances than those of the single data-based models not considering connect methods. The CSP performance of the other models falls somewhere in between. It is concluded that the WOE-RF is the most appropriate coupled condition for CSP than the other models.

Colorimetric Determination of Urea in Feeds

1963 ◽  
Vol 46 (2) ◽  
pp. 303-306
Author(s):  
T J Potts
Keyword(s):  
Standard Deviation ◽  
Coefficient Of Variation ◽  
Collaborative Study ◽  
Colorimetric Determination ◽  
Mean Values ◽  
Precision And Accuracy ◽  
Official Procedure

Abstract A collaborative study was undertaken this year on the DMAB method for the colorimetric determination of urea in dry corn samples, which was compared with method 22.023-22.024. The DMAB method uses p-dimethylami-nobenzaldehyde as the color producer for spectrophotometry measurement. Mean values showed excellent recovery by both the official procedure and the DMAB procedure. Over-all standard deviation and coefficient of variation for all three dry corn samples containing urea indicated greater precision and accuracy by the DMAB procedure; collaborators expressed preference for this method. Further work is recommended to finalize the determination of urea in feeds.

scholarly journals A statistical study of variability in catch obtained by short repeated trawls taken over an inshore ground

1951 ◽  
Vol 29 (3) ◽  
pp. 649-660 ◽  
Author(s):  
H. Barnes ◽  
T. B. Bagenal
Keyword(s):  
Standard Deviation ◽  
Working Conditions ◽  
Coefficient Of Variation ◽  
Statistical Study ◽  
Sampling Period ◽  
Single Species ◽  
The Other ◽  
Population Changes ◽  
Flat Fish ◽  
The Mean

The variability in catch of a series of hauls with a V.D. trawl taken under, as far as possible, controlled working conditions has been determined.For analysis the species were divided into ‘round’ fish and ‘flat’ fish together with Nephrops; for both groups the coefficient of variation varied from 40 to 85 %. Taking 75 % as a representative value, the 2σ fiducial limits are 30–300 % for a single species from a single haul of half an hour duration.It has been found that the standard deviation is roughly proportional to the mean, and that the variance is greater than the mean and increases with the mean. This suggests aggregation of the population.The species are considered over the whole sampling period (4 weeks). Except for haddocks and dogfish the ‘round’ fish constituted a constant population. Changes were found in the other groups and their origin is discussed.

Producers' Response to Changes in Prices and Marketing Policies: A Case Study of Sugarcane and Paddy in Eastern U.P. by S. C. Gupta and A. Majid. New York: Asia Publishing House, 1965.

1968 ◽  
Vol 8 (2) ◽  
pp. 308-309
Author(s):  
Mohammad Irshad Khan
Keyword(s):  
New York ◽  
Time Series ◽  
Time Series Data ◽  
Publishing House ◽  
Economic Incentives ◽  
The Other ◽  
Series Data ◽  
Poor Countries ◽  
Northern India

It is alleged that the agricultural output in poor countries responds very little to movements in prices and costs because of subsistence-oriented produc¬tion and self-produced inputs. The work of Gupta and Majid is concerned with the empirical verification of the responsiveness of farmers to prices and marketing policies in a backward region. The authors' analysis of the respon¬siveness of farmers to economic incentives is based on two sets of data (concern¬ing sugarcane, cash crop, and paddy, subsistence crop) collected from the district of Deoria in Eastern U.P. (Utter Pradesh) a chronically foodgrain deficit region in northern India. In one set, they have aggregate time-series data at district level and, in the other, they have obtained data from a survey of five villages selected from 170 villages around Padrauna town in Deoria.

scholarly journals Technical note: Inherent benchmark or not? Comparing Nash–Sutcliffe and Kling–Gupta efficiency scores

2019 ◽  
Vol 23 (10) ◽  
pp. 4323-4331 ◽  
Author(s):  
Wouter J. M. Knoben ◽  
Jim E. Freer ◽  
Ross A. Woods
Keyword(s):  
Time Series ◽  
Coefficient Of Variation ◽  
Ad Hoc ◽  
Model Performance ◽  
Technical Note ◽  
Mean Flow ◽  
Model Adequacy ◽  
Robust Model ◽  
The Mean ◽  
Adequacy Assessment

Abstract. A traditional metric used in hydrology to summarize model performance is the Nash–Sutcliffe efficiency (NSE). Increasingly an alternative metric, the Kling–Gupta efficiency (KGE), is used instead. When NSE is used, NSE = 0 corresponds to using the mean flow as a benchmark predictor. The same reasoning is applied in various studies that use KGE as a metric: negative KGE values are viewed as bad model performance, and only positive values are seen as good model performance. Here we show that using the mean flow as a predictor does not result in KGE = 0, but instead KGE =1-√2≈-0.41. Thus, KGE values greater than −0.41 indicate that a model improves upon the mean flow benchmark – even if the model's KGE value is negative. NSE and KGE values cannot be directly compared, because their relationship is non-unique and depends in part on the coefficient of variation of the observed time series. Therefore, modellers who use the KGE metric should not let their understanding of NSE values guide them in interpreting KGE values and instead develop new understanding based on the constitutive parts of the KGE metric and the explicit use of benchmark values to compare KGE scores against. More generally, a strong case can be made for moving away from ad hoc use of aggregated efficiency metrics and towards a framework based on purpose-dependent evaluation metrics and benchmarks that allows for more robust model adequacy assessment.

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