Density-Dependent Suppression of Experimentally Created Gypsy Moth, Lymantria dispar (Lepidoptera: Lymantriidae), Populations by Natural Enemies

Gould, Juli R.; Elkinton, Joseph S.; Wallner, William E.

doi:10.2307/5169

Cited by 111 publications

(74 citation statements)

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“…For example, we cannot rule out the possibility that the t Ϫ 1 delayed density-dependent factor that inf luenced T. viridana populations (Figs. 4B and 5B) ref lected a rapid response in space by some natural enemy (32). It is only in combination with experimental studies that have demonstrated the importance of competition that we can be reasonably sure that resource limitation was responsible for the patterns that emerged.…”

Section: Resultsmentioning

confidence: 94%

Estimating the relative roles of top-down and bottom-up forces on insect herbivore populations: A classic study revisited

Hunter

Varley

Gradwell

1997

Proc. Natl. Acad. Sci. U.S.A.

160

123

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Although most ecologists agree that both top-down and bottom-up forces (predation and resource limitation, respectively) act in concert to inf luence populations of herbivores, it has proven difficult to estimate the relative contributions of such forces in terrestrial systems. Using a combination of time-series analysis of population counts recorded over 16 years and experimental data, we present the first estimates of the relative roles of top-down and bottom-up forces on the population dynamics of two terrestrial insect herbivores on the English oak (Quercus robur). Data suggest that temporal variation in winter moth, Operophtera brumata, density is dominated by time-lagged effects of pupal predators. By comparison, spatial variation in O. brumata density is dominated by host-plant quality. Overall, top-down forces explain 34.2% of population variance, bottom-up forces explain 17.2% of population variance, and 48.6% remains unexplained. In contrast, populations of the green oak tortrix, Tortrix viridana, appear dominated by bottom-up forces. Resource limitation, expressed as intraspecific competition among larvae for oak leaves, explains 29.4% of population variance. Host quality effects explain an additional 5.7% of population variance. We detected no major top-down effects on T. viridana populations. An unknown factor causing a linear decline in T. viridana populations over the 16-year study period accounts for most of the remaining unexplained variance. We discuss the observed differences between the insect species and the utility of time-series analysis as a tool in assessing the relative importance of top-down and bottom-up forces on herbivore populations.

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Section: Resultsmentioning

confidence: 94%

Estimating the relative roles of top-down and bottom-up forces on insect herbivore populations: A classic study revisited

Hunter

Varley

Gradwell

1997

Proc. Natl. Acad. Sci. U.S.A.

160

123

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“…Final gypsy moth densities were considerably higher in 1988 than in 1987 in seven of the eight field plots based on fall egg mass counts (Table 2). Plot designations are the same as those used by Gould et al (1990). In 1988, the most substantial drop in gypsy moth density occurred between late instars, pupal and adult stages (Fig.…”

Section: Resultsmentioning

confidence: 99%

Population Regulation of Gypsy Moth (Lepidoptera: Lymantriidae) by Parasitoids: Does Spatial Density Dependence Lead to Temporal Density Dependence?

Ferguson

Elkinton

Gould

et al. 1994

Environmental Entomology

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In 1987, four gypsy moth, Lymantria dispar, (L.) densities were established in eight I-ha plots in western Massachusetts, ranging from 50,000 to 1.4 M neonates per hectare. Two tachinid parasitoid species, Compsilura concinnata (Meigen) and Parasetigena silvestris (Robineau-Desvoidy), exhibited spatial density-dependent parasistism and C. concinnata was the major source of gypsy moth mortality. This study investigated whether spatial density-dependent mortality in 1987 translated into temporal densitydependent mortality of experimental gypsy moth populations created the following year (1988). C. concinnata was responsible for the largest percentage of gypsy moth mortality again in 1988, however, overall mortality caused by C. concinnata in 1988 was considerably less than in 1987. Gypsy moth mortality caused by P. silvestris was greater in 1988. The killing power of either parasitoid in 1988 were not linearly related to the estimated density of the parasitoids produced in the previous year. We saw no evidence for a between-generation numerical response (l-ha scale) of either the generalist parasitoid, C. concinnata, or the specialist parasitoid, P. silvestris, between 1987 and 1988.

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“…Historically, before the fungus arrived in the USA, the virus caused epizootics ending host outbreaks [57] and the community of introduced parasitoids caused higher mortality than we found [46,47]. The fungal pathogen now outcompetes parasitoids within gypsy moth caterpillars at a range of host densities.…”

Section: Resultsmentioning

confidence: 42%

“…R. Soc. B 283: 20160154 contrast, studies conducted before E. maimaiga was established reported higher levels of both parasitoids and virus [46,47], including high co-infection of LdMNPV with tachinid flies during a viral epizootic [48].…”

Section: Discussion (A) Co-infection Of Gypsy Moth Larvae By Multiplementioning

confidence: 99%

Fatal diseases and parasitoids: from competition to facilitation in a shared host

Hajek

Nouhuys

2016

Proc. R. Soc. B.

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Diverse parasite taxa share hosts both at the population level and within individual hosts, and their interactions, ranging from competitive exclusion to facilitation, can drive community structure and dynamics. Emergent pathogens have the potential to greatly alter community interactions. We found that an emergent fungal entomopathogen dominated pre-existing lethal parasites in populations of the forest defoliating gypsy moth, Lymantria dispar. The parasite community was composed of the fungus and four parasitoid species that only develop successfully after they kill the host, and a virus that produces viable propagules before the host has died. A low-density site was sampled over 17 years and compared with 66 sites across a range of host densities, including outbreaks. The emergent fungal pathogen and competing parasitoids rarely co-infected host individuals because each taxa must kill its host. The virus was not present at low host densities, but successfully co-infected with all other parasite species. In fact, there was facilitation between the virus and one parasitoid species hosting a polydnavirus. This newly formed parasite community, altered by an emergent pathogen, is shaped both by parasite response to host density and relative abilities of parasites to co-inhabit the same host individuals.

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Density-Dependent Suppression of Experimentally Created Gypsy Moth, Lymantria dispar (Lepidoptera: Lymantriidae), Populations by Natural Enemies

Cited by 111 publications

References 0 publications

Estimating the relative roles of top-down and bottom-up forces on insect herbivore populations: A classic study revisited

Estimating the relative roles of top-down and bottom-up forces on insect herbivore populations: A classic study revisited

Population Regulation of Gypsy Moth (Lepidoptera: Lymantriidae) by Parasitoids: Does Spatial Density Dependence Lead to Temporal Density Dependence?

Fatal diseases and parasitoids: from competition to facilitation in a shared host

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