Contemporaneous Mortality Factors in Population Dynamics

1965 ◽  
Vol 97 (11) ◽  
pp. 1173-1184 ◽  
Author(s):  
R. F. Morris
Keyword(s):  
Population Dynamics ◽  
Statistical Inference ◽  
Direct Observation ◽  
General Equation ◽  
Population Data ◽  
Interaction Coefficient ◽  
Field Population ◽  
Population Trend ◽  
Mortality Factor ◽  
Mortality Factors

AbstractThe effect of any mortality factor on population trend is influenced greatly by other factors that operate contemporaneously within the same age interval, and by the extent to which it interacts with these other factors. A general equation which makes provision for different degrees of interaction is proposed as a simplified first step in the study of interaction, and some theoretical examples are presented to illustrate the importance of the interaction coefficient. Methods for obtaining estimates of the coefficient, both through statistical inference from field population data and through direct observation and experimentation, are discussed.

Major Factors in Survival of the Immature Stages of Pieris rapae (L.)

1966 ◽  
Vol 98 (6) ◽  
pp. 653-662 ◽  
Author(s):  
D. G. Harcourt
Keyword(s):  
Population Dynamics ◽  
Survival Rate ◽  
Pieris Rapae ◽  
Pupal Stage ◽  
Population Data ◽  
Life Tables ◽  
Immature Stages ◽  
Mortality Factors ◽  
Key Factor ◽  
Major Factors

AbstractDetailed studies on the population dynamics of the imported cabbageworm, Pieris rapae (L.), have been carried out at Merivale, Ontario, since 1959. A method for preparing life tables is described and a mean life table is presented for 18 generations of the species on cabbage. Population data for the preadult period show that there are three age intervals during which extensive mortality may occur: (1) between hatching and the second moult, (2) instars three to five, and (3) during the pupal stage. The analysis of successive age-interval survivals in relation to generation survival showed that the latter is largely determined by the survival rate for (2). Examination of the life tables revealed that a granulosis of the larvae caused by a capsule virus is the key factor in generation survival. Major mortality factors include rainfall and parasites.

Population Dynamics of the Larch Sawfly

1964 ◽  
Vol 96 (1-2) ◽  
pp. 160-161 ◽  
Author(s):  
Keyword(s):  
Biological Control ◽  
Population Dynamics ◽  
Life Table ◽  
Quantitative Methods ◽  
Population Data ◽  
Natural Control ◽  
Mortality Factors ◽  
Ecological Relationships ◽  
Pristiphora Erichsonii ◽  
Larch Sawfly

The larch sawfly, Pristiphora erichsonii (Htg.), has been studied in Manitoba for over 50 years, since the first outbreaks led to the introduction of the European parasite, Mesoleius tenthredinis Morley. This parasite was credited with reducing the severity of early outbreaks but when host populations again increased in the early 1940's, it was found that M. tenthredinis was ineffective due to the ability of host larvae to encapsulate parasite eggs. Intensive studies of individual mortality factors were initiated at the Winnipeg Laboratory as staff and facilities were expanded in the late 1940's. Development of the life-table concept of recording population data (Morris and Miller 1954) led to co-ordination of several projects until by 1955 a team of research officers was engaged in comprehensive studies of general ecological relationships, parasitism, vertebrate predation, and the effect of defoliation on host stands. Members of the team currently engaged in population dynamics studies and responsible for this exhibit are: Dr.C. H. Buckner, vertebrate predators; W. G. H. Ives, quantitative methods and natural control; L. D. Nairn, interrelations with host tree; Dr. W. J. Turnock, natural and biological control, bioclimatology. Other Winnipeg officers working on related larch sawfly projects are Dr. R. J. Heron, physiological studies, and J. A. Muldrew, biological control with particular reference to immunity to M. tenthredinis.

An analysis of the population dynamics of the Jamaican sugar-cane pest Saccharosydne saccharivora (Westw.) (Hom., Delphacidae)

1972 ◽  
Vol 62 (1) ◽  
pp. 73-85 ◽  
Author(s):  
J. R Metcalfe
Keyword(s):  
Population Dynamics ◽  
Selective Breeding ◽  
Population Analysis ◽  
Graphical Analysis ◽  
Leaf Nitrogen ◽  
Mortality Factor ◽  
Agricultural Practice ◽  
Mortality Factors ◽  
Density Dependent ◽  
Key Factor

The Varley & Gradwell method of population analysis is applied to data on populations of Saccharosydne saccharivora (Westw.), comprising 51 generations from 21 fields, obtained in Jamaica in 1961–62. Populations were estimated at five points in each generation, namely, maximum potential natality, and numbers of eggs laid, instar 1, peak instars 3–5, and of normal reproducing adults. Taking maximum potential natality as the first point in each life budget, graphical analysis showed that the key factor was mortality between instar 1 and reproducing adults or between peak instars 3–5 and reproducing adults. Reduced fecundity, due to submaximal leaf nitrogen, was density independent or possibly inversely density dependent; one egg parasite, Tetrastichus sp., was inversely density dependent while another, Anagrus flaveolus Waterh., and an undetermined egg mortality factor were density independent; parasitism of nymphs and presumably adults also by Stenocranophilus quadratus Pierce was density dependent, and was Considered to be the only regulating factor. The key factor was density independent, and it is concluded that, of the separate mortality factors contained within it, dispersal of adults is the most important. This itself depends on crop characters which could be altered by selective breeding or agricultural practice.

scholarly journals Two methods of assessing the mortality factors affecting the larvae and pupae of Cameraria ohridella in the leaves of Aesculus hippocastanum in Switzerland and Bulgaria

2007 ◽  
Vol 97 (5) ◽  
pp. 445-453 ◽  
Author(s):  
S. Girardoz ◽  
R. Tomov ◽  
R. Eschen ◽  
D.L.J. Quicke ◽  
M. Kenis
Keyword(s):  
Leaf Senescence ◽  
Sampling Method ◽  
Plant Defence ◽  
Leaf Miner ◽  
Mortality Factor ◽  
Horse Chestnut ◽  
Mortality Factors ◽  
Grab Sampling ◽  
Defence Reaction ◽  
Factors Affecting

AbstractThe horse-chestnut leaf miner, Cameraria ohridella, is an invasive alien species defoliating horse-chestnut, a popular ornamental tree in Europe. This paper presents quantitative data on mortality factors affecting larvae and pupae of the leaf miner in Switzerland and Bulgaria, both in urban and forest environments. Two sampling methods were used and compared: a cohort method, consisting of the surveying of pre-selected mines throughout their development, and a grab sampling method, consisting of single sets of leaves collected and dissected at regular intervals. The total mortality per generation varied between 14 and 99%. Mortality was caused by a variety of factors, including parasitism, host feeding, predation by birds and arthropods, plant defence reaction, leaf senescence, intra-specific competition and inter-specific competition with a fungal disease. Significant interactions were found between mortality factors and sampling methods, countries, environments and generation. No mortality factor was dominant throughout the sites, generations and methods tested. Plant defence reactions constituted the main mortality factor for the first two larval stages, whereas predation by birds and arthropods and parasitism were more important in older larvae and pupae. Mortality caused by leaf senescence was often the dominant mortality factor in the last annual generation. The cohort method detected higher mortality rates than the grab sampling method. In particular, mortality by plant defence reaction and leaf senescence were better assessed using the cohort method, which is, therefore, recommended for life table studies on leaf miners.

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