The Construction, Description, and Analysis of Age-Specific Life-Tables

Methods for constructing a life-table and budget for a species are described, and the various methods for the analysis of stage-frequency data reviewed. Stage-frequency data comprise counts of the individuals in different development stages in samples taken from a population over a period of time. The analysis of stage-frequency data to estimate the durations of the stages, the numbers entering stages, and survival rates is described. Examples of survivorship curves are presented, and the calculation of population growth rate described. Analysis of life-table data and demographic methods, including key-factor analysis, are described.

A study on first citations of patents through a combination of Bradford’s distribution, Cox regression and life tables method

The current research employs two survival analysis methods: Cox regression and life tables. The first determines the effect of inventor, assignee and country for receiving the first citation by patents. Life tables concern the time-lag between the dates of granting and receiving the first citation by patents. Bradford’s method is also established as a technique for categorization of patents, inventors, assignees and countries as a prerequisite for survival analysis. The research materials consist of 2837 patents in the area of ‘purification, separation, or recovery of hydrocarbon components’ which were classified under the classes 585/800 and 585/868 by the United States Patent and Trademark Office (USPTO). The findings showed that Bradford’s method complies with the distribution of citations of patents, first inventors and assignees. It means that Bradford’s distribution is well suited for determination of key patents, inventors and assignees in an area too. Cox regression revealed that only the inventors’ variable decides for receiving the first citation in terms of frequency, degrees of their inventions and citations. Life table data revealed that one half of the first citations were received in the first 10 years. As a conclusion, survival analysis methods provide the possibility for deciding technology lifetime and for predicting the determinants for the flow of knowledge through citation analysis.

Effects of constant and fluctuating temperatures on development and reproduction of Megoura crassicauda and Aphis craccivora (Hemiptera: Aphididae)

The influence of fluctuating temperatures on the development and fecundity of two aphids, Megoura crassicauda Mordvilko and Aphis craccivora Koch, were determined by collecting life table data at a constant temperature (22 °C) and two fluctuating temperatures (22 ± 3 °C and 22 ± 5 °C). The longevity of M. crassicauda decreased significantly at 22 ± 3 °C and 22 ± 5 °C, while there was no significant difference in the longevity of A. craccivora among the three treatments. The fecundity and intrinsic rate of increase (r) of M. crassicauda decreased significantly at both fluctuating temperatures, while A. craccivora showed the opposite tendency. These results showed that the fluctuating temperatures had negative impacts on the life history traits of M. crassicauda, but were beneficial for A. craccivora. Data obtained under constant temperatures may not reveal accurately enough the biotic responses of pests in the field.

Afit: a bioinformatic tool for measuring aphid fitness and invasiveness

A careful measure of fitness represents a crucial target in crop pest management and becomes fundamental considering extremely prolific insects. In the present paper, we describe a standardized rearing protocol and a bioinformatics tool to calculate aphid fitness indices and invasiveness starting from life table data. We tested the protocol and the bioinformatic tool using six Myzus persicae (Sulzer) asexual lineages in order to investigate if karyotype rearrangements and ecotype could influence their reproductive performances. The tool showed that different karyotypes do not influence adaptive success and put in evidence a marked invasive potential of the M. persicae lineage 64. The presence of a similar fitness rate of 33H and 7GK asexual lineages (both possessing intra-individual karyotype variations) in respect to the asexual lineage 1 (with a standard karyotype) represents an important demonstration of the potentiality of holocentric chromosomes to reduce the effects of chromosome rearrangements.