HOST LARVAL MORTALITY IN AN EXPERIMENTAL HOST–PARASITE POPULATION

1964 ◽  
Vol 42 (5) ◽  
pp. 745-765 ◽  
Author(s):  
T. Burnett
Keyword(s):  
Larval Mortality ◽  
Trialeurodes Vaporariorum ◽  
Parasite Population ◽  
Rapid Decline ◽  
Encarsia Formosa ◽  
Host Protection ◽  
Host Mortality ◽  
Host Parasite ◽  
Parasite Populations ◽  
Two Populations

Two populations of Trialeurodes vaporariorum (Westw.) and its chalcid parasite Encarsia formosa Gahan were reared on tomato plants in the greenhouse at 72–76 °F for 26 weeks. Although the abundance of both species fluctuated with peaks of increasing amplitude, the population that was initially larger remained so throughout the period of sampling because the parasite inflicted similar rates of mortality in both cases. The fluctuations of the two separate populations were synchronized throughout the period of propagation. Host mortality, which resulted either from almost immediate killing of host scales following attack by adult parasites or from death of host larvae following parasitization and development of parasite progeny, was determined by parasite density, host size, and possibly by a number of other factors such as the age structure of host larval populations, age of adult parasites, and succulence of leaves on which the host larvae developed. The interaction of host and parasite produced cycles in the age structures of host and parasite populations that, in turn, influenced the interaction of the two species. The death of host larvae following attack by adult parasites was a form of host protection, as it ensured the rapid decline in the abundance of the parasite population and was, therefore, the primary factor in the maintenance of the host–parasite system.

ASPECTS OF THE INTERACTION BETWEEN A CHALCID PARASITE AND ITS ALEURODID HOST

1967 ◽  
Vol 45 (4) ◽  
pp. 539-578 ◽  
Author(s):  
T. Burnett
Keyword(s):  
Larval Mortality ◽  
Trialeurodes Vaporariorum ◽  
Host Population ◽  
Population Variation ◽  
Encarsia Formosa ◽  
Greenhouse Whitefly ◽  
Parasite Abundance ◽  
Tomato Plants ◽  
Host Mortality ◽  
Dominant Process

Three populations of the greenhouse whitefly, Trialeurodes vaporariorum, and its chalcid parasite Encarsia formosa were propagated each year for three consecutive years on tomato plants in the greenhouse. The abundance of the host and parasite species fluctuated either with peaks of increasing amplitude, with peaks of decreasing amplitude, or with irregular peaks. The dominant process in the interaction was the occurrence of two qualitatively different types of host larval mortality: (a) parasitization, and (b) almost immediate killing after attack by adult parasites. Fluctuations in host and parasite abundance resulted from the almost immediate killing of small host larvae and the death of the short-lived adult parasites. The parasite population tended to destroy similar percentages of host populations of different densities but host mortality was also related to the age structure of the host population. Variation in host reproduction, caused by differences in rearing temperature and by seasonal variation in the physical environment, influenced host and parasite densities.

An Effect of Parasite Attack on Host Mortality, as Exemplified by Encarsia formosa and Trialeurodes vaporariorum

1962 ◽  
Vol 94 (7) ◽  
pp. 673-679 ◽  
Author(s):  
T. Burnett
Keyword(s):  
Field Tests ◽  
Trialeurodes Vaporariorum ◽  
Host Feeding ◽  
Encarsia Formosa ◽  
Mature Adult ◽  
Bracon Hebetor ◽  
Black Scale ◽  
Host Mortality ◽  
Host Parasite ◽  
Juvenilizing Effect

It is not unusual for parasite attack on insect hosts to have different consequences for individuals of the same species. An indication of the variation in types of alternative effects is given by a consideration of three host-parasite relationships. First, although most hosts in a population are susceptible to parasitization, some are immune to attack: about one in 3,000 larvae of the Mediterranean flour moth, Anagasta kühniella (Zeller), was found by Payne (1934) to be immune to attack by Bracon hebetor Say. Second, tile morphology of hosts may be modified differentially by parasitism: unhatched eggs of Aphdius platensis Brethes exert a juvenilizing effect on nymphs of Aphis craccivora Koch whereas parasite larvae sometimes cause the appearance of adult characters (Johnson, 1959). Third, some hosts are successfully parasitized whereas others are killed long before parasite progeny can mature: adult females of Metaphycus helvolus (Com.) kill the black scale, Saissetin oleae (Bern.), by parasitization, by mutilation with the ovipositor, and by host-feeding at wounds made by the ovipositor. Field tests showed that up to 97 per cent of a black-scale infestation may be killed by the parasite over a period of several months.

AN INSECT HOST–PARASITE POPULATION

1960 ◽  
Vol 38 (1) ◽  
pp. 57-75 ◽  
Author(s):  
Thomas Burnett
Keyword(s):  
General Trend ◽  
Trialeurodes Vaporariorum ◽  
Parasite Population ◽  
Insect Host ◽  
Growth Forms ◽  
Encarsia Formosa ◽  
Tomato Plants ◽  
Sources Of Variation ◽  
Host Parasite

Eight populations of Trialeurodes vaporariorum and Encarsia formosa were propagated on tomato plants in the greenhouse for about eight months. Although there was some variation in the growth-forms of host and parasite among the experiments, the general trend in each experiment was one of fluctuations of slightly, but distinctly, increasing amplitude. As extraneous sources of variation had only a slight influence on the growth-forms, the fluctuations resulted from host–parasite interaction. The T. vaporariorum – E. formosa system, is well suited for an investigation of the principles of host–parasite interaction.

scholarly journals Diversity patterns in parasite populations capable for persistence and reinfection with a view towards thehuman cytomegalovirus

2019 ◽  
Author(s):  
Cornelia Pokalyuk ◽  
Irene Görzer
Keyword(s):  
Balancing Selection ◽  
Parasite Population ◽  
Substantial Fraction ◽  
Diversity Patterns ◽  
Coding Regions ◽  
Evolutionary Advantage ◽  
Parasite Reproduction ◽  
Host Parasite ◽  
Parasite Populations ◽  
High Diversity

AbstractMany parasites like thecytomegalovirus, HIVandEscherichia coliare capable to persist in and reinfect its host. The evolutionary advantage (if so) of these complicated mechanisms have not been quantitatively analyzed so far. Here we take a first step by investigating a host-parasite model for which these mechanisms are driving the evolution of the parasite population. We consider two variants of the model. In one variant parasite reproduction is directed by balancing selection, in the other variant parasite reproduction is neutral. In the former scenario reinfection and persistence have been shown to sustain the maintenance of diversity in the parasite population in certain parameter regimes (Pokalyuk and Wakolbinger, 2018). Here we analyse the diversity patterns in the latter, neutral scenario. We evaluate the biological relevance of both model variants with respect to thehuman cytomegalovirus(HCMV), an ancient herpesvirus that is carried by a substantial fraction of mankind and manages to maintain a high diversity in its coding regions.

Processes influencing the distribution of parasite numbers within host populations with special emphasis on parasite-induced host mortalities

Parasitology ◽  
1982 ◽  
Vol 85 (2) ◽  
pp. 373-398 ◽  
Author(s):  
R. M. Anderson ◽  
D. M. Gordon
Keyword(s):  
Probability Models ◽  
Natural Habitats ◽  
Parasite Abundance ◽  
Convex Curves ◽  
Different Types ◽  
Demographic Processes ◽  
Host Mortality ◽  
Over Dispersion ◽  
Host Parasite ◽  
Parasite Populations

SUMMARYThe paper examines the factors which generate various patterns of dispersion in the distribution of parasites within their host populations. Particular emphasis is placed on the role played by chance elements in the growth and decay of parasite populations and on the influence of different types of demographic processes. It is argued that observed distributions are dynamic, rather than static, entities generated by opposing forces, some acting to create over-dispersion and others acting to generate under-dispersion. Monte Carlo simulation experiments, based on probability models of the growth and decay of host and parasite populations, are used to study the dynamics of parasite dispersion. Attention is specifically focused on the role played by parasite-induced host mortality. It is shown that, for certain types of host–parasite associations, convex curves of mean parasite abundance in relation to age (age-intensity curves), concomitant with a decline in the degree of dispersion in the older age classes of hosts, may be evidence of the induction of host mortality by parasite infection. Empirical evidence is examined in light of this prediction. In general, however, simulation studies highlight the technical difficulties inherent in establishing clear evidence of parasite-induced host mortality from ecological studies of hosts and parasites in their natural habitats.

EFFECTS OF INITIAL DENSITIES AND PERIODS OF INFESTATION ON THE GROWTH-FORMS OF A HOST AND PARASITE POPULATION

1960 ◽  
Vol 38 (6) ◽  
pp. 1063-1077 ◽  
Author(s):  
T. Burnett
Keyword(s):  
Trialeurodes Vaporariorum ◽  
Parasite Population ◽  
Growth Forms ◽  
Encarsia Formosa

Initial densities and periods of infestation of adults of Trialeurodes vaporariorum and its chalcid parasite Encarsia formosa influence subsequent fluctuations in numbers of adults of both host and parasite.

scholarly journals Host “cleansing zone” at secondary contact: a new pattern in host-parasite population genetics

2020 ◽  
Author(s):  
Jana Martinů ◽  
Jan Štefka ◽  
Anbu Poosakkannu ◽  
Václav Hypša
Keyword(s):  
Population Genetics ◽  
Generation Time ◽  
Population Genetic ◽  
Parasite Population ◽  
Secondary Contact ◽  
Mitochondrial Genomes ◽  
Isolated Populations ◽  
Host Parasite ◽  
Parasite Populations ◽  
Complete Mitochondrial Genomes

AbstractWe introduce a new pattern of population genetic structure in a host-parasite system that can arise after secondary contact (SC) of previously isolated populations. Due to different generation time and therefore different tempo of molecular evolution the host and parasite populations reach different degrees of genetic differentiation during their separation (e.g. in refugia). Consequently, during the SC the host populations are able to re-establish a single panmictic population across the whole recolonized area, while the parasite populations stop their dispersal at the SC zone and create a narrow hybrid zone (HZ). From the host’s perspective, the parasite’s HZ functions on a microevolutionary scale as a “host-cleansing filter”: while passing from area A to area B, the hosts are rid of the area A parasites and acquire the area B parasites. We demonstrate this novel pattern on a model composed of Apodemus mice and Polyplax lice by comparing maternally inherited markers (complete mitochondrial genomes, and complete genomes of vertically transmitted symbiont Legionella polyplacis) with SNPs derived from the louse genomic data. We discuss circumstances which may lead to this pattern and possible reasons why it has been overlooked in the studies on host-parasite population genetics.

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