Stable Age Distribution

2016 ◽  
Author(s):  
Monica Nordberg ◽  
Douglas M. Templeton ◽  
Ole Andersen ◽  
John H. Duffus
Keyword(s):  
Age Distribution ◽  
Stable Age Distribution

scholarly journals STUDI LALAT PENGOROK DAUN LIRIOMYZA SPP. PADA PERTANAMAN BAWANG DAUN, DAN PARASITOID OPIUS CHROMATOMYIAE BELOKOBYLSKIJ & WHARTON (HYMENOPTERA: BRACONIDAE)

2009 ◽  
Vol 9 (1) ◽  
pp. 22-31
Author(s):  
Rusli Rustam ◽  
Aunu Rauf ◽  
Nina Maryana ◽  
Pudjianto Pudjianto ◽  
Dadang Dadang
Keyword(s):  
Age Distribution ◽  
Host Density ◽  
Field Studies ◽  
Reproductive Value ◽  
Laboratory Studies ◽  
Demographic Parameter ◽  
Liriomyza Huidobrensis ◽  
Stable Age Distribution ◽  
Net Reproduction ◽  
Density Results

Studies on Leafminer Liriomyza spp. in Green Onion Fields, and Parasitoid Opius chromatomyiae Belokobylskij & Wharton (Hymenoptera: Braconidae).  Field studies were conducted to determine population abundance of leafminers and their parasitoids in green onion fields in Puncak, West Java. In addition to that, laboratory studies were carried out to determine demographic parameter of Opius chromatomyiae as well as response of parasitoid to increasing host density. Results revealed that green onions were infested by two species of leafminers, Liriomyza huidobrensis and Liriomyza chinensis.  Leafminer flies emerged from Erwor leaves (54.5) were significantly higher than those of RP leaves (18.65) (P = 0.0005). However, number of  leafminer flies caught on sticky traps was not statistically different (P = 0.297).  Two species of parasitoid, Hemiptarsenus varicornis and O. chromatomyiae, were associated with leafminers in green onion fields. Higher number of parasitoids emerged from Erwor leaves (13.68) as compared to RP (6.90) (P =0.0007 ). However, level of parasitization were 24.36% on Erwor and 28.45% on RP, and was not significantly different (P = 0.387). Laboratory studies indicated that net reproduction (Ro) of O. chromatomyiae was 28.55, generation time (T) 15.96 days, intrinsic growth rate 0.21, and total of reproductive value 223.64.  The stable age distribution of parasitoid were 37.93% eggs, 24.92% larvae, 20.36% pupae and 16.78% adults.  The parasitoid showed functional response type II to increasing host density, with a = 0.08 and Th = 2.58.

scholarly journals The long-term effects of the Amoco Cadiz oil spill

1982 ◽  
Vol 297 (1087) ◽  
pp. 323-333 ◽  
Keyword(s):  
Salt Marshes ◽  
Age Distribution ◽  
Life Cycles ◽  
Long Term Effects ◽  
Delayed Effects ◽  
Sea Birds ◽  
Stable Age Distribution ◽  
Rot Disease ◽  
One Year

The supertanker Amoco Cadiz wrecked on the coast of northern Brittany in April 1978. The resulting spill of 223000 t of crude oil polluted some 360 km of rocky or sandy shores, salt marshes and estuaries. An immediate mortality impact was observed. Populations of bivalves, periwinkles, limpets, peracarid crustaceans, heart urchins and sea birds were the most severely affected. Populations of polychaete worms, large crustaceans and coastal fishes were less affected. Three to six generations (5—10 years for bivalves but up to 60 years for birds) may be necessary before populations retrieve their stable age distribution. Delayed effects on mortality, growth and recruitment were still observed up to 3 years after the spill. Estuarine flat fishes and mullets had reduced growth, fecundity and recruitment; they were affected by fin rot disease. Populations of clams and nematodes in the meiofauna declined one year after the spill. Weathered oil is still present in low-energy areas. Species with short life cycles tend to replace long-lived species. A fauna of cirratulid and capitellid polychaete worms now prevails in sandy to m uddy areas. For several clam populations, recruitment remains unstable. Three years after the spill it is still premature to decide how long it will take before populations and ecosystems reach their former or new equilibria.

Chapter 1: Theoretical Foundations

1973 ◽  
Vol 27 ◽  
pp. 6-10 ◽  
Author(s):  
Kenneth M. Weiss
Keyword(s):  
Age Distribution ◽  
Human Populations ◽  
Stable Form ◽  
Stable Age Distribution ◽  
Theoretical Population ◽  
Stable Population Theory ◽  
Number Of Individuals ◽  
Theoretical Foundations ◽  
Stable Populations

The approach to population structure followed in this work is that of stable population theory as developed by A. J. Lotka and others. An early exposition of this theory is found in Lotka (1956); more recently it has been summarized by Coale (1972), Keyfitz (1968), and Shryock and Siegel(1971).The theory of stable populations requires that a population is infinite in size, has no net immigration or outmigration, and has fixed rates of fertility and mortality at each age. These assumptions are often approximated closely enough by real populations for the theory to be useful. Given the stated conditions, a population is described by its age distribution, or the number of individuals at each age. Since the theoretical population is infinite, the age distribution is defined in terms of relative numbers or percentages rather than finite numbers of individuals at each age.The age structure is determined by the rates of mortality and fertility. It has been proved by Lotka that, no matter what the initial age distribution, a population under these assumptions approaches a certain age distribution which is determined by those rates. The result is the so-called stable age distribution since it will no longer change if mortality and fertility remain fixed. In fact, a temporary perturbation in these rates will only temporarily disturb the age distribution, which will quickly return to the stable form. Human populations approach the stable age distribution in well under 100 yr after the rates become fixed.

Exponential growth of a branching process usually implies stable age distribution

1979 ◽  
Vol 16 (03) ◽  
pp. 651-656
Author(s):  
Bo Berndtsson ◽  
Peter Jagers
Keyword(s):  
Population Size ◽  
Exponential Function ◽  
Exponential Growth ◽  
Branching Process ◽  
Age Distribution ◽  
Length Distribution ◽  
Random Variables ◽  
Stable Age Distribution

Start a Bellman–Harris branching process from one or several ancestors, whose ages are identically distributed random variables. Assume that the life-length distribution decays more quickly than exponentially and that the distribution of ages at start does not give too much mass to high ages (in a sense to be made precise). Then, if the expected population size is an exponential function of time, the ages must follow the stable age distribution of the process.

The growth and composition of branching populations

1984 ◽  
Vol 16 (2) ◽  
pp. 221-259 ◽  
Author(s):  
Peter Jagers ◽  
Olle Nerman
Keyword(s):  
Exponential Growth ◽  
Probability Space ◽  
Point Processes ◽  
Age Distribution ◽  
Single Type ◽  
Survey Paper ◽  
Stable Age Distribution ◽  
Definition Of ◽  
Counting Yield ◽  
Strict Definition

A single-type general branching population develops by individuals reproducing according to i.i.d. point processes on R+, interpreted as the individuals' ages. Such a population can be measured or counted in many different ways: those born, those alive or in some sub-phase of life, for example. Special choices of reproduction point process and counting yield the classical Galton–Watson or Bellman–Harris process. This reasonably self-contained survey paper discusses the exponential growth of such populations, in the supercritical case, and the asymptotic stability of composition according to very general ways of counting. The outcome is a strict definition of a stable population in exponential growth, as a probability space, a margin of which is the well-known stable age distribution.

Exponential growth of a branching process usually implies stable age distribution

1979 ◽  
Vol 16 (3) ◽  
pp. 651-656 ◽  
Author(s):  
Bo Berndtsson ◽  
Peter Jagers
Keyword(s):  
Population Size ◽  
Exponential Function ◽  
Exponential Growth ◽  
Branching Process ◽  
Age Distribution ◽  
Length Distribution ◽  
Random Variables ◽  
Stable Age Distribution

Start a Bellman–Harris branching process from one or several ancestors, whose ages are identically distributed random variables. Assume that the life-length distribution decays more quickly than exponentially and that the distribution of ages at start does not give too much mass to high ages (in a sense to be made precise). Then, if the expected population size is an exponential function of time, the ages must follow the stable age distribution of the process.

The effect of temperature, humidity and quantity of food on the development and diapause of Trogoderma parabile Beal.

1961 ◽  
Vol 51 (4) ◽  
pp. 685-696 ◽  
Author(s):  
H. D. Burges
Keyword(s):  
Egg Production ◽  
Age Distribution ◽  
Effect Of Temperature ◽  
Female Adult ◽  
Large Size ◽  
Limited Success ◽  
Rate Of Increase ◽  
Stable Age Distribution ◽  
Adult Lives ◽  
Active Adults

The rate of development and the egg-production of the Dermestid beetle, Trogoderma parabile Beal, at 30°C. and 60 to 70 per cent. R.H. and the effect upon larval development of the volume of food, the temperature and the relative humidity have been determined.In 15 to 450 cc. of wheatfeed at 30°C. and 60 to 70 per cent. E.H., active adults are formed from eggs in a mean of 39 days (egg 6, larva 26, pupa 5 and pre-emergence 2). Males develop slightly more rapidly than females. On average, a female adult lives 8 days and 53 of her offspring reach maturity. The weekly rate of increase of a population of stable age distribution (A) is × l·7.At temperatures between 17·5 and 37·5°C. (and at 70 per cent. R.H.) and at humidities between near 0 and 90 per cent. R.H. (and 30°C.) larvae can grow to a large size; but in 0·7 to 25 cc. of food some of these large larvae enter a facultative diapause, as a result of restricted space. Disturbance of the food increases the proportion of diapause larvae. The diapause larvae feed and moult intermittently. At 30°C. and 60–70 per cent. R.H., a period of seven weeks after hatching has been adopted arbitrarily to distinguish diapause and non-diapause larvae. Only a limited success was obtained in breaking the diapause, which is less readily broken than that of T. granarium Everts.

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