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Maria Björkman Peter A. Hambäck Richard J. Hopkins Birgitta Rämert 《Agricultural and Forest Entomology》2010,12(2):123-132
- 1 The relative importance of the resource concentration hypothesis and the enemies hypothesis was investigated for the turnip root fly Delia floralis in a cabbage–red clover intercropping system compared with a cabbage monoculture.
- 2 Delia floralis egg densities were measured as well as the activity‐densities of generalist predators in a field experiment during two growing seasons. In the second year, a study of egg predation with artificially placed eggs was conducted, in addition to a predator exclusion experiment, to estimate total predation during the season. Parasitization rates were estimated from samples of pupae.
- 3 Delia floralis oviposition was greater in the monoculture during both years. The predator activity‐densities differed between treatments and study years. The known natural enemies of Delia spp., Bembidion spp. and Aleochara bipustulata showed a strong response to a cultivation system with higher activity‐densities in the monoculture. The response, however, appeared to be caused primarily by habitat preferences and not by D. floralis egg densities.
- 4 The reduction in the number of D. floralis pupae in the intercropping may be explained by a disruption in oviposition behaviour caused by the presence of clover because neither predation, nor parasitization rates differed between cultivation systems.
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Takayuki Ohgushi 《Population Ecology》1988,30(1):57-68
The relationships between egg predation of an herbivorous lady beetle Epilachna niponica (Lewis ) and its predator, the earwig Anechura harmandi (Burr ), were examined in both time and space. In spite of little annual, changes in egg densities, egg mortality due to predation varied considerably. There was no, clear relationship between the earwig density and the proportionate predation over the five years. The seasonal occurrence of earwig nymphs on thistle plants, however, was closely synchronized with that of egg predation. Predator attacks on the beetle occurred in a time-restricted manner. Thus, later cohorts mostly escape from heavy predatory pressure. No spatially density-depent egg predation was detected at the level of either thistle plants or thistle patches. Furthermore, there was no indication of aggregative behaviour of the earwig in response to local egg density. The earwig density was more likely to be associated with particular localities with sandy deposits available for its nest site. 相似文献
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Jan H. Mol 《Oecologia》1996,107(3):395-410
This study investigated the role of predators in preventing competitive exclusion among three closely related armoured catfishes (Callichthys callichthys, Hoplosternum littorale and H. thoracatum) that occur synthopically in multi-predator freshwater swamps of Suriname, South America. The potential impact of predation on armoured catfish was determined by combining laboratory measurements of predation rates on five early developmental stages of the armoured catfish H. thoracatum for 24 aquatic predators with field studies of the density of the predators in the swamps. The contribution of a particular predator to the total predation pressure on its prey was determined to a large extent by the density of the predator in the swamp. Seemingly innocuous predators with low or moderate predation rates in the laboratory may be extremely important in the swamps due to their high abundance. Small-sized omnivorous fishes and aquatic invertebrates were major predators of early developmental stages of armoured catfish. Both qualitative and quantitative ontogenetic changes in the predation pressure on armoured catfish were observed. Major predation on eggs, larvae and juveniles of H. thoracatum resulted from a different set of predators in each developmental stage of the prey. In all developmental stages of H. thoracatum the predation pressure involved several predator species and not a single, dominant predator. The potential predation pressure of the 24 predators taken together and the number of predators that were able to prey on H. thoracatum decreased sharply with increasing age (size) of the prey. Even if egg (nest) predation is prevented by the guarding male, the potential impact of the 24 predators on the populations of armoured catfish is large. Predation may account for the high mortality of H. thoracatum observed in the swamps. The high predation pressure on callichthyid catfishes may help to explain the coexistence of three closely related and morphologically quite similar armoured catfishes in Surinamese swamps. 相似文献
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Felix J. J. A. Bianchi Nancy A. Schellhorn Saul A. Cunningham 《Agricultural and Forest Entomology》2013,15(1):12-23
- 1 Landscape management for enhanced natural pest control requires knowledge of the ecological function of the habitats present in the landscape mosaic. However, little is known about which habitat types in agricultural landscapes function as reproduction habitats for arthropod pests and predators during different times of the year.
- 2 We studied the arthropod assemblage on six crops and on the seven most abundant native plant species in two landscapes over 1 year in Australia. Densities of immature and adult stages of pests and their predators were assessed using beat sheet sampling.
- 3 The native plants supported a significantly different arthropod assemblage than crops. Native plants had higher predator densities than crops over the course of the year, whereas crops supported higher pest densities than the native plants in two out of four seasonal sampling periods. Crops had higher densities of immature stages of pests than native plants in three of four seasonal sampling periods, implying that crops are more strongly associated with pest reproduction than native plants. Densities of immature predators, excluding spiders, were not different between native plants and crops. Spiders were, however, generally abundant and densities were higher on native plants than on crops but, because some species disperse when immature, there is less certainty in identifying their reproduction habitat.
- 4 Because the predator to pest ratio on native plant species showed little variation, and spatial variation in arthropod assemblages was limited, the predator support function of native vegetation may be a general phenomenon. Incentives that maintain and restore native remnant vegetation can increase the predator to pest ratio at the landscape scale, which could enhance pest suppression in crops.
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The impact of predation on Helicoverpa armigera was studied in four field cage exclusion trials on cotton in Kenya. H. armigera egg cohorts were introduced inside predator‐free and open control cages, and the impact of local predator populations on the cohort was examined. Fourteen days after inoculation, exclusion cages had four times more larvae than controls, indicating a strong impact of predation. Ants and Anthocoridae were the predominant predator groups. Exclusion cages had more damaged fruiting plant parts (squares, flowers and bolls) than the control. In the absence of predators, natural mortality of H. armigera was greater as cotton matured, and is likely to be linked to the host plant condition. 相似文献
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Prey are often consumed by multiple predator species. Predation rates on shared prey species measured in isolation often do
not combine additively due to interference or facilitation among the predator species. Furthermore, the strength of predator
interactions and resulting prey mortality may change with habitat type. We experimentally examined predation on amphipods
in rock and algal habitats by two species of intertidal crabs, Hemigrapsus sanguineus (top predators) and Carcinus maenas (intermediate predators). Algae provided a safer habitat for amphipods when they were exposed to only a single predator species.
When both predator species were present, mortality of amphipods was less than additive in both habitats. However, amphipod
mortality was reduced more in rock than algal habitat because intermediate predators were less protected in rock habitat and
were increasingly targeted by omnivorous top predators. We found that prey mortality in general was reduced by (1) altered
foraging behavior of intermediate predators in the presence of top predators, (2) top predators switching to foraging on intermediate
predators rather than shared prey, and (3) density reduction of intermediate predators. The relative importance of these three
mechanisms was the same in both habitats; however, the magnitude of each was greater in rock habitat. Our study demonstrates
that the strength of specific mechanisms of interference between top and intermediate predators can be quantified but cautions
that these results may be habitat specific.
An erratum to this article can be found at 相似文献
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Yasutomo Higashiura 《Population Ecology》1980,22(1):147-162
- Birds’ predation on gypsy moth egg masses deposited on tree trunks was quantitatively evaluated in a birch forest at Bibai, Hokkaido during the four winter seasons from 1974 to 1978.
- Holling's disc-equation could be successfully applied to describe the relationship between the total egg consumption by birds and the density of egg masses. A rapid method for fitting the disc-equation to observed data was proposed based on the study byShinozaki andKira (1961).
- Appreciable amounts of predation were observed only during the period when the depth of snow cover on the ground exceeded 1 m, while the egg masses deposited on lower parts of tree trunk below 1 m level suffered from only slight predation. It was therefore presumed that deep snow cover made the predator birds to change their feeding place from ground vegetation to tree trunks.
- The duration of the period with snow accumulation deeper than 1 m was introduced into the disc-equation as an additional parameter. The values calculated by the resultant formulation agreed with the observed values in respective years satisfactorily.
- There were circumstantial evidences that the great tit, Parus major, was one of the important predators concerned.
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- Population responses to extrinsic mortality can yield no change in the number of survivors (compensation) or an increase in the number of survivors (overcompensation) when the population is regulated by negative density‐dependence. This intriguing response has been the subject of theoretical studies, but few experiments have explored how the source of extrinsic mortality affects the response.
- This study tests abilities of three functionally diverse predators, alone and combined, to induce (over)compensation of a prey population. Larval Aedes aegypti (Diptera: Culicidae) were exposed to predation by Mesocyclops longisetus (Crustacea: Copepoda), Anopheles barberi (Diptera: Culicidae), Corethrella appendiculata (Diptera: Corethrellidae), all three in a substitutive design, or no predation.
- Predator treatment had no significant effect on the total number of adult survivors, nor on numbers of surviving males or females. The female development rate and a composite index of performance (r′) were greater with predation relative to no‐predator control. No differences were detected between diverse and single‐species predator treatments.
- Sensitivity analyses indicated predation effects on the number of female adults produced, despite not being affected significantly, was the largest contributing factor to significant treatment effects on the demographic index r′. While predation did not significantly increase the production of adults, it did release survivors from density‐dependent effects sufficiently to increase population performance. This study provides an empirical test of mechanisms by which predation may yield positive mortality effects on victim populations, a phenomenon predicted to occur across many taxa and food webs.
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J.R. Hagler 《The Annals of applied biology》2006,149(2):153-165
A simplified but highly effective approach for the post‐mortem evaluation of predation on several targeted members of an arthropod assemblage that does not require the development of pest‐specific enzyme‐linked immunosorbent assay (ELISA) (e.g. pest‐specific monoclonal antibodies) or PCR assays (DNA primers) is described. Laboratory feeding studies were conducted to determine if predation events could be detected from predators that consumed prey marked with foreign protein. I determined that large and small rabbit immunoglobulin G (IgG)‐marked prey can be detected by a rabbit‐IgG‐specific ELISA in the guts of chewing and piercing–sucking type predators. I then conducted multifaceted inclusion and exclusion field cage studies to qualify the degree of interguild and intraguild predation occurring among a complex arthropod assemblage during four separate light phase treatments. The field cages contained an arthropod assemblage consisting of 11 or 12 species of predaceous arthropods and three pest species. The three pests introduced into the cages included third instar Trichoplusia ni marked with rabbit IgG, third instar Lygus hesperus marked with chicken IgG and Pectinophora gossypiella sentinel egg masses. The inclusion cages allowed foraging fire ants, Solenopis xyloni, to freely enter the cages while the exclusion cages contained barriers that prevented ant entry. The results obtained using the conventional inclusion/exclusion field cage methodology revealed that there was substantial interguild and intraguild predation occurring on the majority of the arthropods in the assemblage, particularly in those cages that included ants. I then precisely identified which predators in the assemblage were feeding on the three targeted pests by conducting three post‐mortem gut content analyses on each individual predator (1503 individuals) in the assemblage. Specifically, P. gossypiella egg predation events were detected using an established P. gossypiella‐egg‐specific ELISA, and third instar T. ni and L. hesperus predation events were detected using rabbit‐IgG‐specific and chicken‐IgG‐specific ELISAs, respectively. Generally, the gut ELISAs revealed that Collops vittatus, Spanagonicus albofasciatus and Geocoris punctipes readily preyed on P. gossypiella eggs; Nabis alternatus, Zelus renardii and spiders (primarily Misumenops celer) readily preyed on marked L. hesperus nymphs, and spiders, S. albofasciatus and N. alternatus readily preyed on T. ni larvae. Furthermore, the cage methods and the post‐mortem predator gut ELISAs revealed very few distinctive patterns of predation with regard to the light cycle the assemblage was exposed to. 相似文献
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Mutual interference between predatory anthocorids 总被引：1，自引：0，他引：1
H. F. EVANS 《Ecological Entomology》1976,1(4):283-286
- 1 The way in which the predator Anthocoris confusus reacts to the presence of other individuals of the same species is described.
- 2 Mutual interference between adult A.confusus leads to a density-dependent decrease in egg production, due mainly to an increased tendency to migrate from areas of high predator density.
- 3 Even when ten first instar predators were present in a 2 cm diameter cage they did not interfere with each other unless the amount of food available was inadequate for survival.
- 4 Mutual interference between A.confusus adults promotes stability in populations of the predator and will lead to even exploitation of an unevenly distributed food source.