Spatial Variations in Host Density and the Intensity of Parasitism: Some Empirical Examples

Morrison, Gerold; Strong, Donald R.

doi:10.1093/ee/9.2.149

Cited by 84 publications

(55 citation statements)

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“…Indeed, it is quite likely t o find a positive aggregative response leading to an inverse density dependent relationship between per cent parasitism and host density per patch. This range of patterns for the spatial distribution of parasitism has already been noted by Morrison et al (1 980) and Morrison & Strong (1980, 1981. They stress that in analysing relationships between parasitism and host density per patch, it is necessary to account for both the proportion of patches discovered and, within these, the proportions of host parasitized.…”

Section: Introductionsupporting

confidence: 54%

Patterns of parasitism by insect parasitoids in patchy environments

Hassell

1982

Ecological Entomology

110

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1. This paper shows how the different spatial patterns of per cent parasitism in patches of different host density can be explained within a single model framework that takes into account the parasitoid's aggregative response, and the factors limiting the degree of host exploitation within patches. 2. Two contrasting laboratory examples are presented in which the distribution of searching parasitoids and the resulting levels of parasitism in different patches are both known for a range of parasitoid densities. 3. A model is described predicting the number of hosts parasitized per patch, in which the number of parasitoids searching is determined from a simple expression allowing different degrees of aggregation. 4. The model generates patterns of parasitism encompassing the two laboratory examples and a wide range of examples from the field.5. The importance of density dependent spatial distributions of parasitism to population stability is briefly discussed.

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Section: Introductionsupporting

confidence: 54%

Patterns of parasitism by insect parasitoids in patchy environments

Hassell

1982

Ecological Entomology

110

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“…Despite these common beliefs, many studies have failed to detect direct spatial density dependence (e.g., Morrison and Strong 1980, Lessells 1985, Duan et al 1998. Indeed, limits to either the number of host larvae or the time available for searching, because of time taken to "handle" hosts, can result in under-exploitation of high density patches, i.e., inverse density dependence.…”

Section: Discussionmentioning

confidence: 99%

Occurrence of Emerald Ash Borer (Coleoptera: Buprestidae) and Biotic Factors Affecting Its Immature Stages in the Russian Far East

Duan¹,

Yurchenko²,

Fuester³

2012

env. entom.

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Field surveys were conducted from 2008 to 2011 in the Khabarovsk and Vladivostok regions of Russia to investigate the occurrence of emerald ash borer, Agrilus planipennis Fairmaire, and mortality factors affecting its immature stages. We found emerald ash borer infesting both introduced North American green ash (Fraxinus pennsylvanica Marshall) and native oriental ashes (F. mandshurica Rupr. and F. rhynchophylla Hance) in both regions. Emerald ash borer densities (larvae/m(2) of phloem area) were markedly higher on green ash (11.3-76.7 in the Khabarovsk area and 77-245 in the Vladivostok area) than on artificially stressed Manchurian ash (2.2) or Oriental ash (10-59). Mortality of emerald ash borer larvae caused by different biotic factors (woodpecker predation, host plant resistance and/or undetermined diseases, and parasitism) varied with date, site, and ash species. In general, predation of emerald ash borer larvae by woodpeckers was low. While low rates (3-27%) of emerald ash borer larval mortality were caused by undetermined biotic factors on green ash between 2009 and 2011, higher rates (26-95%) of emerald ash borer larval mortality were caused by putative plant resistance in Oriental ash species in both regions. Little (<1%) parasitism of emerald ash borer larvae was observed in Khabarovsk; however, three hymenopteran parasitoids (Spathius sp., Atanycolus nigriventris Vojnovskaja-Krieger, and Tetrastichus planipennisi Yang) were observed attacking third - fourth instars of emerald ash borer in the Vladivostok area, parasitizing 0-8.3% of emerald ash borer larvae infesting Oriental ash trees and 7.3-62.7% of those on green ash trees (primarily by Spathius sp.) in two of the three study sites. Relevance of these findings to the classical biological control of emerald ash borer in newly invaded regions is discussed.

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“…Most research on natural enemies has been limited to interactions between enemies and victims. Many authors believe that enemies tend to aggregate, on some scales at least, in areas of high victim density (reviewed by Hassell [1978Hassell [ , 1982, but see Morrison and Strong [1980]). By itself, a strong enemy aggregation response might be predicted in some situations to counteract concentration of oligophagous herbivores in simple habitats.…”

Section: Importance or Interactions Between Plants And Generalist Enementioning

confidence: 99%

Response by Specialist and Generalist Natural Enemies to Agroecosystem Diversification: A Selective Review

Sheehan¹

1986

Environmental Entomology

179

112

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Spatial Variations in Host Density and the Intensity of Parasitism: Some Empirical Examples

Cited by 84 publications

References 0 publications

Patterns of parasitism by insect parasitoids in patchy environments

Patterns of parasitism by insect parasitoids in patchy environments

Occurrence of Emerald Ash Borer (Coleoptera: Buprestidae) and Biotic Factors Affecting Its Immature Stages in the Russian Far East

Response by Specialist and Generalist Natural Enemies to Agroecosystem Diversification: A Selective Review

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