Life Table Data Research Articles

Life table responses of zooplankton ( Moina micrura Kurz and Daphnia carinata King) to manure application in a culture system

Neonates or adults of Moina micrura and Daphnia carinata were individually dispensed into culture tubes suspended in each of three replicate tanks representing treatments differing in days (2, 4, 6, 9 and 11 days) after manure (cattle manure, poultry droppings, and mustard oil cake, 1:1:1) application. The cladocerans in the culture tubes were examined daily to collect life table data. Primary productivity values and water quality parameters were determined. Time to first reproduction ( A) was delayed during the early part of manure application. Mean longevity ( W), total offspring production ( S), reproductive life span, net reproductive rate ( R o), average generation time ( T c), intrinsic rate of natural increase ( r) and finite rate ( e r) of the test cladocerans were reduced 2 days after application compared with 11 days after application. Differences in offspring production of test cladocerans in five different treatments were directly conrrelated with gross or net primary productivity values but inversely correlated with increasing levels of ammonia-N.

Tobacco control and health expectancy in Australia

Correspondence to : Dr Holman. Abstract Objective To model the effects of suc cessful tobacco control on health expect ancy in a developed country. Design A comparison was made of ex pected numbers of years spent in different conditions of health and institutional care between actual and a hypothetical using Australian life table and cross sectional health survey data. Subjects Adult Australians aged 18 years and older. Main outcome measure Health expect ancies at age 18 years were expressed as the remaining years of life spent in fair to excellent health or in poor health, or occupying a bed in a short-stay hospital or in a long-stay health establishment. Results In non-smoking Australia, pro jected length of life in fair to excellent health increased by 3.67 years (males) and 1.40 years (females). Time spent in the community in poor health fell by 0.66 years (males) and 0.30 years (females). Expected duration of bed occupancy in creased in non-smoking Australia by about 0.01-0.02 years for short-stay hos pitalisation and by 0.08-0.09 years for long-term health establishments. Conclusion Elimination of exposure to tobacco smoke in Australia is expected to increase life expectancy with no unto ward consequences for the prevalence of ill-health.

The epidemiology of traumatic death. A population-based analysis.

Despite the proliferation of trauma systems, there are no population-based data describing the epidemiology of traumatic death. To provide these data, we reviewed all trauma deaths occurring in San Diego (California) County during 1 year. There were 625 traumatic deaths during the study (27.3 deaths per 100,000 population per year). Motor vehicle trauma was the most common cause of injury leading to death (N = 344 [55.2%]; 15.0 annual deaths per 100,000 population). Central nervous system injuries were the most common cause of death (48.5%, or 13.2 deaths per 100,000 population per year). Sepsis was responsible for only 2.5% of the overall mortality. Based on life-table data, traumatic death resulted in an annual loss of 1091 years of life per 100,000 and an annual loss of 492 years of productivity per 100,000. Injury continues to account for an enormous loss of life despite improvements in survival wrought by trauma systems.

The natural history of congenital myotonic dystrophy: mortality and long term clinical aspects.

Although the genetic basis of the congenital form of myotonic dystrophy has recently been clarified, data as to outcome in terms of life expectancy and morbidity are scanty. Life table data based on a cohort of 115 patients with a confirmed diagnosis of congenital myotonic dystrophy are presented. The data suggest a 25% chance of death before 18 months of age and a 50% chance of survival into the mid-30s. The profile of disease and complications among survivors is also charted.

Life tables and intrinsic rate of natural increase ofPediobius furvus [Hym.: Eulophidae] onChilo partellus [Lep.: Pyralidae

In the present studies, life table data and intrinsic rate of natural increase (rm) of the eulophid pupal parasitoid,P. furvus (Gahan) were obtained fromChilo partellus (Swinhoe) at a constant temperature of 26.7±0.6°C, 52.3±2.7% RH in the laboratory. Development of immature stages took 19.1±0.3 days; adult females lived for 7.9±3.3 (range, 2–13) days and produced a mean of 91.9±22.4 progeny per female, with a sex ratio of 1:2.9 (♂:♀). The intrinsic rate of natural increase (rm) was 0.2558/female/day; the net reproductive rate (R0), 237.25; the capacity for increase (rc) of 0.252; and the finite rate of increase (λ) of 1.29/female/day; thus, each female contributed 231.42 individuals to the population in a mean generation time of 21.38 days.

Comments on ‘Some results on the Gompertz and Heligman and Pollard laws of mortality’

AbstractThe consequences of graduating truncated English Life Table data by either the Gompertz or truncated Heligman and Pollard ‘laws of mortality’, recently advocated by Thatcher (1990), are examined in greater detail.

Instar-Specific Morphometrics and Linear Discriminant Models for Age-Grading Field Populations of Acyrthosiphon kondoi (Homoptera: Aphididae)

Reliable criteria for age-grading field-collected Acyrthosiphon kondoi Shinji are of critical importance for proper development and interpretations of time-specific life table data. Classification criteria in the form of linear discriminant models were developed for laboratory populations of A. kondoi using measurements of several body structures. These models were further validated using field-collected aphids from 11 locations across Oklahoma over a period of 2 yr. Despite greater variability and generally larger size of aphids in field populations, linear discriminant models provided highly accurate (>99%) criteria for identifying all instars. Misclassification was observed only in the first instar, where 0.9% of nymphs were classified as second instars. To attain this degree of accuracy in classifying individuals from field populations, lengths of cornicles, first flagellar segments, and fore tibiae are required.

Natural Enemies of the Legume Pod Borer, Maruca Testulalis Geyer (Lepidoptera: Pyralidae) in Small Scale Farming Systems of Western Kenya

Studies at ICIPE’s Mbita Point Field Station (site 1) and a farmer’s field in Lambwe Valley (site 2) in Western Kenya, revealed the presence of at least seven parasitoids, two predators, one nematode and several microorganic pathogens attacking Maruca testulalis on cowpea crop. Some parasitoids and pathogens were also recovered from M. testulalis cadavers collected on wild host plants of the pest. A pupal endoparasitoid, Antrocephalus sp. was the most predominant, while the pathogens Nosema sp. and Bacillus sp. caused the highest natural mortality on M. testulalis in this region. Parasitoids and pathogens contributed 40.65 and 35.6% to the total generation mortality (K) at sites 1 and 2 respectively. Observed parasitism only contributed 3.25% at site 1 and 3.8% at site 2 of the generation mortality. Mortality due to disappearance which included predation accounted for 59.35 and 64.8% of K at the respective sites. Life table data and survival curves for the pest revealed high generation mortality (ca. 98%), most of which occurred in the early life stages of the pest. The results suggest a high potential for utilizing biocontrol agents in IPM of the pest.

Biology of Trichobaris bridwelli (Coleoptera: Curculionidae), a Possible Agent for the Biological Control of Datura stramonium (Solanaceae)

The weevil Trichobaris bridwelli Barber is a natural enemy of jimsonweed ( Datura stramonium L.) in the southern United States. The temporal distribution of all life stages showed that T. bridwelli is bivoltine in central Texas and overwinters principally in the adult stage inside the seed capsules of jimsonweed. Females oviposited in the leaves, flowers, and capsules. Subsequent development occurred both in the stems and capsules of its host plant. All life stages of T. bridwelli were attacked by hymenopterous parasitoids; Anaphes sp. and Microctonus sp. are new host records. In the laboratory, adult females lived an average of 16.1 wk and deposited an average of 324 eggs. Development in the laboratory required 37.8 d: egg 5.9 d, larval stage 20.2 d, prepupal period about 3 d, and pupal stage 8.7 d. The intrinsic rate of increase ( T m) of T. bridwelli was calculated from laboratory life table data to be 0.41 at 24°C. T. bridwelli was evaluated for its potential effectiveness as a biological control agent of jimsonweed and possibly chinese thornapple, Datura ferox L. Although T. bridwelli did not complete development on a critical test plant (tobacco) under laboratory conditions, extensive host specificity testing should be conducted to determine the limits of its host range.

Tsetse fly (Diptera: Glossinidae) population dynamics and the estimation of mortality rates from life-table data

AbstractThe estimation of tsetse fly mortality rates from life-table data is central to opulation dynamics studies and to the development of tsetse fly control programmes. For a population at equilibrium with a stable age distribution, the age-specific mortalities may be estimated directly from the number of individuals in each age class, but a correction must be applied when the population is growing or declining. Furthermore, if the mortality rates are changing with time, inaccuracies will be introduced into estimates of the mortality rates derived from the age structure of the population since the population will take time to reach a new stable age distribution. In this paper we use the Euler-Lotka equation, which relates the age-specific mortality and fecundity to the overall growth rate of the population, to study the loss rate of the tsetse flyGlossina pallidipes(Austen) as a function of pupal mortality, adult mortality and mortalities applied to each age class seperately. We then present a simulation model in order to quantity and to set limits on the precision of estimates of mortalities when the mortalities are themselves changing.

SIMULATED MANAGEMENT OF AN HISTORICAL SPRUCE BUDWORM POPULATION USING INUNDATIVE PARASITE RELEASE

AbstractSummary life table data of historical spruce budworm, Choristoneura fumiferana (Clemens), populations from the Green River Project in New Brunswick, Canada (1947–1958), provided information for developing a management strategy using annual inundative releases of the egg parasite Trichogramma minutum Riley. Three threshold levels (39, 169, and 201 budworm egg masses per 10 m2 foliage) were assigned to the spruce budworm population and a simulation model employed to manage it at or below each level. Based on field data, the lowest threshold represented a light level of defoliation while the other two thresholds represented moderate defoliation levels. With the exception of 3 years at the low level, annual inundative releases of T. minutum successfully suppressed the spruce budworm population below the three thresholds in the model. Annual releases of T. minutum were also simulated during the inclining, plateau, and declining phases of one outbreak cycle of the spruce budworm. At the same rate (12 × 106 female T. minutum per hectare), inundative releases during the inclining phase were more effective than during either the plateau or declining phases. The results suggest that some low and moderate populations of spruce budworm can be effectively managed using annual inundative releases of an egg parasite, particularly toward the end of the inclining phase of an outbreak, but when populations reach severe levels, additional mortality agents probably will have to be considered in an integrated approach.

Fate of patients undergoing transluminal angioplasty for lower-limb ischemia.

A prospective study of 370 patients who underwent 500 percutaneous transluminal angioplasties (PTAs) for lower-limb ischemia over a 7-year period was performed. A 97% follow-up rate was achieved. The first PTA was successful in 188 patients (51%). Of the failures, 31% were failed attempts at dilation and 73% occurred within 1 month of intervention. Of the patients with failed PTA, 39% underwent bypass surgery and 24% underwent amputation. The 30-day mortality rate was 3%, with 1% of the deaths attributed to PTA. The survival rate at 5 years for the successes was double that for the failures (P less than .0005). The best results were in femoropopliteal stenoses with two or three patent calf vessels (cumulative patency rate, 78% at 3 years) and the worst in femoropopliteal occlusions with one or no patent calf vessels (cumulative patency rate, 25% at 3 years). Log rank tests on the life-table data were used to show factors favoring a good outcome. It is concluded that PTA is the treatment of first choice in suitable patients and, although the failure of intervention in critical ischemia has a significant risk, it is a valuable addition to the therapeutic options in patients with little chance of surgical treatment.

Competing risk analysis of life table data: Application to lifetime risk computation

In this pedagogic note we propose to assess the safety of treatment in a clinical trial, or the effect of risk exposure in a chronic animal study, in terms of two lifetime risks. These risks are computable from fife table type data and take into account the effects of competing risks. We first describe their computational procedures in detail to demonstrate the need for their implementation in a computer program. We then illustrate their practical application through use of the data obtained from an actual clinical study.

The effect of spatial pattern on community dynamics; a comparison of simulated and field data

The effect of the spatial limits of dispersal and competition on plant community dynamics was studied using Monte-Carlo simulation. The model generates community point patterns, using life-table data, dispersion parameters and radii of competitive effects. These data have been estimated in a field situation, for the 11 most abundant weed species growing on the refuse soil dumps of a strip coal mine. In a simulation experiment, the patterns produced by two versions of the model were compared. The first was based on the field situation as much as possible; the other used the same input parameters except for dispersal, which was randomized in this case. We found considerable differences regarding the temporal changes of species abundances, the realized competitive abilities and the spatial patterns generated by the two versions. An important conclusion of this comparison is that the realized competitive effect (both intra-and interspecific) of a species is dependent not only on constant competition parameters, but on the abundance relations and on the spatial patterns of the competing populations as well. It is concluded that the spatial limits of dispersal and competition may result in the increased persistence of weak competitors, moderate the realized competitive effects of strong species, and shape the spatial coalition structure of the community.

Mathematical hazard models of mortality: an alternative to model life tables.

A five-parameter competing hazard model of the age pattern of mortality is described, and methods of fitting it to survivorship, death rate, and age structure data are developed and presented. The methods are then applied to published life table and census data to construct life tables for a Late Woodland population, a Christian period Nubian population, and the Yanomama. The advantage of this approach over the use of model life tables is that the hazard model facilitates life-table construction without imposing a particular age pattern of mortality on the data. This development makes it possible to use anthropological data to extend the study of human variation in mortality patterns to small populations.

A mathematical model of survival in relation to age and sex of cancer patients

The mathematical model assumes that following treatment there are two groups of patients, with P proportion in the “cured” group and (1-P) proportion in the “non-cured” group. Each group has a constant force of survival for each time interval, and that proportion is S1 for the “cured” group and S2 for the “non-cured” group. (Proceedings of the Fifth International Conference on Mathematical Modelling, 1985.) Cancer is predominantly a disease of the aged. It may be assumed that the long term results of treatment will vary with the age of the patients. This study addresses survival in relation to age and sex of the cancer patients, by the stage of the disease. Life-table data has been provided by the Biometry Branch of the National Cancer Institute. The ages of diagnosis are broken down by age groups: under 45, 45 to 54, 55 to 64, 65 to 74 and 75 and over. A computer program has been developed to estimate the three parameters P, S1 and S2. The data analysis reveals that, in general, the proportion of “cured” and survival rate of the “non-cured” group decreases from local, to regional and to distant stages of the disease. However, there are a few exceptions for the oldest age-groups of patients.

Life table tests of evolutionary theories of senescence

The phenomenon of senescence requires both evolutionary and proximate explanations. The most widely accepted evolutionary explanation for senescence is that it never gets exposed to natural selection because environmental hazards kill all individuals before the age at which senescence causes decreased fitness. If this explanation is sufficient, wild populations should not demonstrate senescence, and their mortality rates should therefore remain constant during adult life, except when environmental causes of mortality have recently decreased. The alternative explanation for the persistence of the genes that cause senescence is that they have been selected for because they have pleiotropic effects that are beneficial early in life when the force of selection is strongest. Where this is the case, mortality rates should increase with age in wild populations. A method is described for using life table data to calculate an estimate of the intensity of selection acting on senescence in wild populations. This method is applied to a variety of life tables. The results suggest that pleiotropic genes may be important causes of senescence in some populations, but not in others. This has implications for research on the proximate mechanisms of senescence.

Dynamics of a Nonoutbreak Population of the Douglas-Fir Tussock Moth (Lepidoptera: Lymantriidae) in Southern Oregon

A low-density population of the Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough), was studied for 13 yr in a mixed-conifer forest in south central Oregon. The densities of tussock moth and associated mortalities in each life stage were estimated over seven consecutive generations by sampling larvae and artificially stocking egg masses and pupae. A single census of early larvae was made annually for an additional 6 yr. Mortalities were summarized in life tables, converted to k -values, and analyzed to detect key factors, compensatory interactions, and density dependence. The largest losses in each generation were from the disappearance of larvae and the parasitization of eggs. A large, unexplained error was also present in most generations. None of the estimated mortality factors qualified alone as a key factor; however, the combined parasitization of eggs, larvae, and pupae was more closely related to changes in generation mortality than was predation of these stages. Parasitization was also delayed density-dependent, but predation was independent of density over the 7 yr that life-table data were collected. The major mortality factors interacted in a compensatory way, so that their combined effects for the full 13 yr of the study were delayed density-dependent and regulatory. This parasite/predator-prey system with a time lag apparently explains the low-density oscillation of tussock moth abundance.

Productivity as a Population Performance Index in Life-Cycle Toxicity Tests

Toxicity at the population level is often measured by the intrinsic rate of population increase (rm). In this paper, the biomass turnover ratio (P/B) of a population is introduced as another measure of population performance under toxic stress. An expression is derived by which the intrinsic P/B ratio may be calculated from life-table data. Unlike rm, P/B depends also on the individual growth curve. The theory is exemplified by experimental data on the effect of cadmium on Orohesella cincta (Collembola) from forest soil. The results are compared with seasonal fluctuations of productivity in an unstressed field population. Toxic effects of cadmium appear at a much lower exposure level than would be deduced from the P/B ratio. Some mechanism of compensation seems to be present in that the high natural mortality (by predation) obscures the sublethal effects on growth. This may explain why Collembola can inhabit forest soils which are contaminated to levels far above the no effect level for individual growth.

Spatial heterogeneity, population "regulation" and local extinction in simulated host-parasitoid interactions.

Simulation models have recently been used to suggest that spatial heterogeneity, acting on small spatial scales within local populations, may allow parasitoids and other natural enemies to "regulate" host or prey populations in ways that would not be detected by conventional (k-factor) analyses of life table data. However, additional study of these models suggests that local extinction may be a frequent event in the simulated interactions. The "spreading of risk" concept appears more applicable to the simulated populations than a classical view emphasizing tight regulation around stable equilibrium points. The spreading of risk viewpoint also appears to shed additional light on questions raised in the recent debate between Dempster (1983); Hassel (1985); Dempster and Pollard (1986), concerning the modeling of spatial heterogeneity and "regulation" in temperate-zone insect populations.