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Invertebrate Predators (invertebrate + predator)

Distribution by Scientific Domains

Life Sciences	100%

Distribution within Life Sciences

Ecology & Organismal Biology	25%

Selected Abstracts

The Influence of Invertebrate Predators on Daphnia Spatial Distribution and Survival in Laboratory Experiments: Support for Daphnia Horizontal Migration in Shallow Lakes

INTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 1 2007
Adrianna Wojtal
Abstract The behavioural response of Daphnia cucullata to the presence of the pelagic invertebrate predator Leptodora kindtii, and the predation rate of littoral dragonfly nymphs on this species were investigated under laboratory conditions. Results of this study revealed a strong hiding response of Daphnia cucullata in the presence of the predatory cladoceran, L. kindtii, which was similar to the response of Daphnia in the presence of juvenile perch. This suggests that pelagic invertebrate predators may cause Daphnia to hide in the littoral zone which could result in increased exposure to predation by littoral invertebrates. A strong influence of dragonfly nymphs on D. cucullata, both in the presence and absence of macrophytes, was found. The average predation rate of Odonata larvae was about 5 prey ind,1 h,1 and did not differ significantly between treatments. Quantification of dragonfly pressure on Daphnia populations will require cross-verification with field experiments since in the natural conditions Daphnia seeks a shelter in the vegetation stands against predation by Leptodora, despite the occurrence of odonates. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Ant versus bird exclusion effects on the arthropod assemblage of an organic citrus grove

ECOLOGICAL ENTOMOLOGY, Issue 3 2010
JOSEP PIÑOL
1. Predation-exclusion experiments have highlighted that top-down control is pervasive in terrestrial communities, but most of these experiments are simplistic in that they only excluded a single group of predators and the effect of removal was evaluated on a few species from the community. The main goal of our study was to experimentally establish the relative effects of ants and birds on the same arthropod assemblage of canopy trees. 2. We conducted 1-year long manipulative experiments in an organic citrus grove intended to quantify the independent effects of bird and ant predators on the abundance of arthropods. Birds were excluded with plastic nets whereas ants were excluded with sticky barriers on the trunks. The sticky barrier also excluded other ground dwelling insects, like the European earwig Forficula auricularia L. 3. Both the exclusion of ants and birds affected the arthropod community of the citrus canopies, but the exclusion of ants was far more important than the exclusion of birds. Indeed, almost all groups of arthropods had higher abundance in ant-excluded than in control trees, whereas only dermapterans were more abundant in bird-excluded than in control trees. A more detailed analysis conducted on spiders also showed that the effect of ant exclusion was limited to a few families rather than being widespread over the entire diverse spectrum of spiders. 4. Our results suggest that the relative importance of vertebrate and invertebrate predators in regulating arthropod populations largely depends on the nature of the predator,prey system. [source]

Impact of avian and arthropod predation on lepidopteran caterpillar densities and plant productivity in an ephemeral agroecosystem

ECOLOGICAL ENTOMOLOGY, Issue 5 2003
Cerruti R. R. Hooks
Abstract., 1.,Most studies evaluating the combined impact of spiders and other predators on herbivore densities in agroecosystems have focused primarily on their trophic connections with invertebrate predators (e.g. carabids, chrysopids); however linkages among spiders and vertebrate predators may also help structure the population dynamics of insect herbivores. A field experiment was conducted to examine the impact of avian and spider predation on lepidopteran caterpillar densities and plant productivity within a Brassica agroecosystem. 2.,Arthropod abundance, leaf-chewing damage, and final plant productivity associated with broccoli, Brassica oleracea L. (var. italica), were recorded for four treatments: (1) bird present but spiders removed; (2) both birds and spiders present; (3) birds excluded, spiders present; and (4) birds and spiders both excluded. 3.,Densities of Artogeia rapae L. (Lepidoptera: Pieridae) and Trichoplusia ni Hübner (Lepidoptera: Noctuidae) large caterpillars and post feeding stages were reduced significantly by bird predation. The abundance of large caterpillars was also reduced on spider-inhabited plants during early plant growth; however the assemblage of birds and spiders did not suppress caterpillar densities more significantly than either predator alone. 4.,Plants protected by birds, spiders, and birds plus spiders sustained less folivory attributable to leaf chewing caterpillars than check plants. Plant productivity was also greater for predator-protected plants than check plants. 5.,Although spiders and parasitoids were responsible for some of the mortality inflicted upon lepidopteran caterpillars, it was concluded that in this study system, birds are the most important natural enemies of folivores. [source]

Do leaf shelters always protect caterpillars from invertebrate predators?

ECOLOGICAL ENTOMOLOGY, Issue 6 2002
Meg T. Jones
Abstract 1. All larval instars of Epargyreus clarus, the silver-spotted skipper, construct and inhabit leaf shelters that are presumed to protect them from predator attack. 2. Shelters effectively protected the larvae against foraging Crematogaster opuntiae ants and naive Polistes spp. wasps in laboratory tests, but did not protect them from predators, largely vespid wasps, present in the field. 3. A range of factors, including type of predator, learning ability, and experience level, may determine the effectiveness of leaf shelters as protection from predators. [source]

Cholinesterase activity and behavior in chlorpyrifos-exposed Rana sphenocephala tadpoles

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2006
Pamela D. Widder
Abstract Recent studies have found a correlation between organophosphate (OP) pesticide exposure and declines in amphibian populations. We evaluated the hypothesis that this relationship is driven by behavioral changes in developing larvae. Specifically, we examined how exposure to a common OP pesticide, chlorpyrifos, influenced cholinesterase (ChE) activity, mass, and swim speed in Rana sphenocephala tadpoles. We also determined how the presence of natural pond sediments in exposure chambers influenced response to the pesticide and how mass and survival were affected when tadpoles were exposed to an invertebrate (odonate) predator in addition to the pesticide. Mass and swim speed were measured after 4- and 12-d laboratory exposures to 1, 10, 100, and 200 ,g/L of chlorpyrifos in test chambers that either did or did not contain pond sediments. These same parameters also were examined in mesocosms dosed with 200 ,g/L of chlorpyrifos to evaluate responses under more environmentally realistic conditions. The effect of the invertebrate predators on survival and/or growth of tadpoles was evaluated in the mesocosm study and in separate laboratory experiments. In laboratory tests, no pesticide-induced mortality was observed; however, tadpole ChE activity in the two highest concentrations was significantly lowered, with a longer exposure duration further decreasing activity (maximum inhibition, 43%). Mass also was lower at higher concentrations, but this effect was not enhanced with longer duration of exposure. Reductions in ChE activity of tadpoles exposed in mesocosms were similar to those observed in laboratory experiments for the first 4 d. Tadpole swim speed and survival in the presence of a predator were not affected, with the latter largely resulting from pesticide-induced predator mortality. [source]

Non-lethal effects of invertebrate predators on Daphnia: morphological and life-history consequences of water mite kairomone

FRESHWATER BIOLOGY, Issue 9 2008
MAURICIO J. CARTER
Summary 1. Here, we report morphological and life-historical changes in the cladoceran Daphnia ambigua in response to chemical cues released by the predatory water mite Piona chilensis. Both species are common inhabitants of southern temperate lakes. 2. We found significant differences in adult body size at first, second and third reproduction. Also, individuals exposed to kairomones had longer tail spines at first reproduction, and the resultant offspring had smaller bodies and shorter tail spines. 3. Exposure to mite cues did not exert effects on brood size at first reproduction, but decreased offspring number in subsequent broods. Similarly, only the second and third reproduction events were delayed by kairomone exposure. 4. The intrinsic population growth rate of predator-induced animals was lower than that in controls, but simulations based on a parameterized matrix model showed that the fitness costs could be overcome if the reported phenotypic responses reduced predation rate moderately. The gain in protection from predators needed to cancel out the reduction in fitness associated with predator cues was directly related to juvenile survival and fertility, and inversely related to adult survival. 5. This is the first work reporting phenotypic plasticity in Cladocera in response to kairomones released by water mites, which are conspicuous predators in many austral fresh waters. [source]

Habitat selection and diel distribution of the crustacean zooplankton from a shallow Mediterranean lake during the turbid and clear water phases

FRESHWATER BIOLOGY, Issue 3 2007
BRUNO B. CASTRO
Summary 1. The fish fauna of many shallow Mediterranean Lakes is dominated by small-bodied exotic omnivores, with potential implications for fish,zooplankton interactions still largely unknown. Here we studied diel variation in the vertical and horizontal distribution of the crustacean plankton in Lake Vela, a shallow polymictic and eutrophic lake. Diel sampling was carried out on three consecutive days along a horizontal transect, including an open-water station and a macrophyte (Nymphaea alba) bed. Since transparency is a key determinant of the predation risk posed by fish, the zooplankton sampling campaigns were conducted in both the turbid (autumn) and clear water (spring) phases. 2. In the turbid phase, most taxa were homogeneously distributed along the vertical and horizontal axes in the three consecutive days. The only exception was for copepod nauplii, which showed vertical heterogeneity, possibly as a response to invertebrate predators. 3. In the clear water phase, most zooplankton taxa displayed habitat selection. Vertically, the general response consisted of a daily vertical migration (DVM), despite the limited depth (1.6 m). Horizontally, zooplankters showed an overall preference for the pelagic zone, independent of the time of the day. Such evidence is contrary to the postulated role of macrophytes as an anti-predator refuge for the zooplankton. 4. These vertical (DVM) and horizontal (macrophyte-avoidance) patterns were particularly conspicuous for large Daphnia, suggesting that predation risk from size-selective predators (fish) was the main factor behind the spatial heterogeneity of zooplankton in the spring. Thus, the difference in the zooplankton spatial distribution pattern and habitat selection among seasons (turbid and clear water phases) seems to be mediated the predation risk from fish, which is directly related to water transparency. 5. The zooplankton in Lake Vela have anti-predator behaviour that minimises predation from fish. We hypothesise that, due to the distinct fish community of shallow Mediterranean lakes, aquatic macrophytes may not provide adequate refuge to zooplankters, as seen in northern temperate lakes. [source]

The Influence of Invertebrate Predators on Daphnia Spatial Distribution and Survival in Laboratory Experiments: Support for Daphnia Horizontal Migration in Shallow Lakes

Prey dispersal rate affects prey species composition and trait diversity in response to multiple predators in metacommunities

JOURNAL OF ANIMAL ECOLOGY, Issue 5 2010
Jennifer G. Howeth
Summary 1.,Recent studies indicate that large-scale spatial processes can alter local community structuring mechanisms to determine local and regional assemblages of predators and their prey. In metacommunities, this may occur when the functional diversity represented in the regional predator species pool interacts with the rate of prey dispersal among local communities to affect prey species diversity and trait composition at multiple scales. 2.,Here, we test for effects of prey dispersal rate and spatially and temporally heterogeneous predation from functionally dissimilar predators on prey structure in pond mesocosm metacommunities. An experimental metacommunity consisted of three pond mesocosm communities supporting two differentially size-selective invertebrate predators and their zooplankton prey. In each metacommunity, two communities maintained constant predation and supported either Gyrinus sp. (Coleoptera) or Notonecta ungulata (Hemiptera) predators generating a spatial prey refuge while the third community supported alternating predation from Gyrinus sp. and N. ungulata generating a temporal prey refuge. Mesocosm metacommunities were connected at either low (0·7% day,1) or high (10% day,1) planktonic prey dispersal. The diversity, composition and body size of zooplankton prey were measured at local and regional (metacommunity) scales. 3.,Metacommunities experiencing the low prey dispersal rate supported the greatest regional prey species diversity (H') and evenness (J'). Neither dispersal rate nor predation regime affected local prey diversity or evenness. The spatial prey refuge at low dispersal maintained the largest difference in species composition and body size diversity between communities under Gyrinus and Notonecta predation, suggesting that species sorting was operating at the low dispersal rate. There was no effect of dispersal rate on species diversity or body size distribution in the temporal prey refuge. 4.,The frequency distribution, but not the range, of prey body sizes within communities depended upon prey dispersal rate and predator identity. Taken together, these results demonstrate that prey dispersal rate can moderate the strength of predation to influence prey species diversity and the local frequency distribution of prey traits in metacommunities supporting ecologically different predators. [source]

The role of trout in stream food webs: integrating evidence from field surveys and experiments

JOURNAL OF ANIMAL ECOLOGY, Issue 2 2006
KRISTIAN MEISSNER
Summary 1We evaluated the effects of brown trout on boreal stream food webs using field surveys and enclosure/exclosure experiments. Experimental results were related to prey preference of uncaged trout in the same stream, as well as to a survey of macroinvertebrate densities in streams with vs. without trout. Finally, we assessed the generality of our findings by examining salmonid predation on three groups of macroinvertebrate prey (chironomid midges, epibenthic grazers, invertebrate predators) in a meta-analysis. 2In a preliminary experiment, invertebrate predators showed a strong negative response to trout, whereas chironomids benefited from trout presence. In the main experiment, trout impact increased with prey size. Trout had the strongest effect on invertebrate predators and cased caddis larvae, whereas Baetis mayfly and chironomid larvae were unaffected. Trout impact on the largest prey seemed mainly consumptive, because prey emigration rates were low and independent of fish presence. Despite strong effects on macroinvertebrates, trout did not induce a trophic cascade on periphyton. Uncaged trout showed a strong preference for the largest prey items (predatory invertebrates and aerial prey), whereas Baetis mayflies and chironomids were avoided by trout. 3Densities of invertebrate predators were significantly higher in troutless streams. Baetis mayflies also were less abundant in trout streams, whereas densities of chironomids were positively, although non-significantly, related to trout presence. Meta-analysis showed a strong negative impact of trout on invertebrate predators, a negative but variable impact on mobile grazers (mainly mayfly larvae) and a slightly positive impact on chironomid larvae. 4Being size-selective predators, salmonid fishes have a strong impact on the largest prey types available, and this effect spans several domains of scale. Discrepancies between our experimental findings and those from the field survey and meta-analysis show, however, that for most lotic prey, small-scale experiments do not reflect fish impact reliably at stream-wide scales. 5Our findings suggest that small-scale experiments will be useful only if the experimental results are evaluated carefully against natural history information about the experimental system and interacting species across a wide array of spatial scales. [source]

Impact of predators on artificially augmented populations of Lymantria dispar L. pupae (Lep., Lymantriidae)

JOURNAL OF APPLIED ENTOMOLOGY, Issue 2-3 2002
T. Gschwantner
The impact of predators on artificially augmented populations of Lymantria dispar pupae (Lep., Lymantriidae) and the species composition of the predator community were investigated in two oak stands in eastern Austria. The population density of L. dispar has been at innocuous levels for several years at both sites. From mid-June to mid-July, we created artificial prey populations by mounting gypsy moth pupae with beeswax on burlap bands placed at the base, 25, 50 and 100 cm height on 25 trees at each site. A total of 6600 pupae were exposed at each site. A total of 92% of exposed pupae were destroyed by predators, at site I (with dense understorey vegetation) whereas 67% were destroyed on site II (with sparse understorey vegetation). Initially, pupal mortality was highest at the base of trees, but differences in mortality among the four locations where pupae were exposed decreased during the course of the study period. Spatial differences in predation were ascertained, suggesting that the aggregation of small mammals, for example, is related to patches of dense shrub vegetation. Pupal mortality was primarily caused by mice (46.3% at site I and 36.4% at site II). Many exposed pupae simply disappeared (40.4% at site I and 22.8% at site II). Calosoma spp. and other invertebrate predators caused very little mortality among L. dispar pupae (5.5% at site I and 7.8% at site II). Trap catches on separate study plots at both sites revealed that Apodemus flavicollis (Rodentia, Muridae) was the most important predator species present, whereas Apodemus sylvaticus (Rodentia, Muridae) and Clethrionomys glareolus (Rodentia, Arvicolidae) were captured in low numbers. [source]

Post-dispersal predation of Taraxacum officinale (dandelion) seed

JOURNAL OF ECOLOGY, Issue 2 2005
ALOIS HONEK
Summary 1The importance of predation in determining the fate of post-dispersal dandelion (Taraxacum officinale) seed was investigated. Flowering, seed dispersal, seedling establishment, seed predation and seed predator abundance were recorded in 2002 and 2003, at two sites. Number of flowers were counted in 1-m2 plots, wind-borne seeds were collected in water traps, invertebrate seed predation was estimated from the rate of removal of dandelion seeds exposed on the ground and invertebrate activity density was determined by using pitfall traps. The censuses were made at 2- to 3-day intervals. 2Seed dispersal occurred 10 days after flowering. Although some seeds were blown away, 3.7,24.2 × 103 seeds m,2 fell to the ground. Four weeks after the peak in seed dispersal 0.7,3.1% of these seeds germinated. Three weeks later only 11,13% of the dispersed seed remained on the ground and most of these were damaged, the remainder presumably having been removed by predators. 3Predation of exposed seeds was low before seed dispersal but increased after its onset, in parallel with increases in the number of seeds present on the ground and in the activity density of adults of a seed-consuming carabid, Amara montivaga. 4In cafeteria experiments in which the seeds of 28 perennial and annual herbs were provided A. montivaga consumed the most dandelion seeds, followed by nine other Amara species. In no-choice experiments, under field conditions, A. montivaga consumed six seeds day,1. 5Post-dispersal predation, mainly due to aggregation of a single ground beetle species, was more important than that which occurred prior to dispersal. Although predators destroyed c. 97% of the seeds, the effect on dandelion population biology is likely to be small. 6Post-dispersal seed predation may nevertheless be important in other species, as aggregates of large invertebrate predators can consume large quantities of seed. [source]

Intraclutch egg-size variation in acanthosomatid bugs: adaptive allocation of maternal investment?

OIKOS, Issue 2 2001
Shin-ichi Kudo
If there are differences in predation risk among the offspring within a clutch, parents may allocate less resources to the offspring facing higher risk. I examined parental investment in terms of egg size within clutches in five species of stink bugs (Heteroptera, Acanthosomatidae). In subsocial Elasmucha and Sastragala species, the female guards her eggs and first-instar nymphs against invertebrate predators by covering her clutch with her body. Large differences in survival from predation between offspring at the centre and offspring at the periphery of the clutch have been reported in such subsocial insects. I found that Elasmucha and Sastragala females laid significantly smaller eggs in the peripheral (and thus more vulnerable) part of the clutch. Phenotypic trade-offs between egg size and clutch size were detected in these subsocial species. Egg size was positively correlated with hatched first-instar nymph size: smaller nymphs hatched from smaller peripheral eggs. In asocial Elasmostethus humeralis, however, no significant difference in size was detected between the eggs at the centre of and those at the periphery of the clutch. Thus, in subsocial acanthosomatid bugs, females seem to allocate their resources according to the different predation risks faced by the offspring within the clutch. [source]

Clay-Turbid Interactions May Not Cascade,A Reminder for Lake Managers

RESTORATION ECOLOGY, Issue 2 2005
Jukka Horppila
Abstract Food web management is a frequently used lake restoration method, which aims to reduce phytoplankton biomass by strengthening herbivorous zooplankton through reduction of planktivorous fish. However, in clay-turbid lakes several factors may reduce the effectivity of food web management. Increasing turbidity reduces the effectivity of fish predation and weakens the link between zooplankton and phytoplankton. Therefore, the effects of fish stock manipulations may not cascade to lower trophic levels as expected. Additionally, in clay-turbid conditions invertebrate predators may coexist in high densities with planktivorous fish and negate the effects of fish reductions. For instance, in the stratifying regions of the clay-turbid Lake Hiidenvesi, Chaoborus flavicans is the main regulator of cladocerans and occupies the water column throughout the day, although planktivorous Osmerus eperlanus is very abundant. The coexistence of chaoborids and fish is facilitated by a metalimnetic turbidity peak, which prevents efficient predation by fish. In the shallow parts of the lake, chaoborids are absent despite high water turbidity. We suggest that, generally, the importance of invertebrate predators in relation to vertebrate predators may change along turbidity and depth gradients. The importance of fish predation is highest in shallow waters with low turbidity. When water depth increases, the importance of fish in the top-down regulation of zooplankton declines, whereas that of chaoborids increases, the change along the depth gradient being moderate in clear-water lakes and steep in highly turbid lakes. Thus, especially deep clay-turbid lakes may be problematic for implementing food web management as a restoration tool. [source]

Effects of off-bottom shellfish aquaculture on winter habitat use by molluscivorous sea ducks

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 1 2009
ydelis
Abstract 1.Shellfish farming is an expanding segment of marine aquaculture, but environmental effects of this industry are only beginning to be considered. 2.The interaction between off-bottom, suspended oyster farming and wintering sea ducks in coastal British Columbia was studied. Specifically, the habitat use of surf scoters (Melanitta perspicillata) and Barrow's goldeneyes (Bucephala islandica), the most abundant sea duck species in the study area, was evaluated in relation to natural environmental attributes and shellfish aquaculture. 3.The extent of shellfish farming was the best-supported habitat variable explaining variation in surf scoter densities, and the only habitat attribute from the considered set that was a strong predictor of Barrow's goldeneye densities. In both cases, the findings indicated strong positive relationships between densities of sea ducks and shellfish aquaculture operations. These relationships are presumably the result of large numbers of wild mussels (Mytilus trossulus) that settle and grow on aquaculture structures and are preferred prey of these sea ducks. 4.Previous work has shown that aquaculture structures provide good conditions for recruiting and growing mussels, including refuge from invertebrate predators, which in turn provides higher densities of higher quality prey for sea ducks than available in intertidal areas. This offers a rare example in which introduction of an industry leads to positive effects on wildlife populations, which is particularly important given persistent declines in numbers of many sea ducks. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Experiments on the mechanism of tree and shrub establishment in temperate grassy woodlands: Seedling emergence

AUSTRAL ECOLOGY, Issue 4 2001
Peter J. Clarke
Abstract Field experiments were designed to examine tree and shrub seedling emergence in temperate grassy woodlands on the New England Tablelands. The effects of study sites, intensity of previous grazing, removal of ground cover by fire or clearing, burial of seeds and ant seed theft on seedling emergence were tested in two field experiments. Six tree and seven shrub species were used in the experiments and their cumulative emergence was compared with laboratory germination studies. All species used in field experiments had lower cumulative emergence than those in laboratory germination studies despite prolonged periods of above average rainfall before and after seeds were sown. Eucalypt species emerged faster in the field than the shrub species and generally attained higher cumulative emergence than the shrubs. Spatial effects of sites and patches within sites, and of previous grazing history did not strongly influence patterns of seedling emergence in most species. Ground and litter cover generally did not enhance or suppress the emergence of seedlings, although the removal of cover in recently grazed areas enhanced the emergence of some species. Burning enhanced the emergence of some tree and shrub species where plots had more fuel and intense fires, but this effect was not strong. Compared with other treatments, seedbed manipulations produced the strongest effects. In the absence of both invertebrate and vertebrate predators, seedling emergence was lower for surface-sown seed, compared with seed sown on scarified soil surfaces. Higher seedling emergence of buried seeds in the presence of invertebrate predators probably resulted from the combined effects of predator escape and enhanced moisture status of the germination environment. Some promotion of emergence was achieved for all species in most sown treatments probably as a result of a prolonged above average rainfall. In contrast, the natural recruitment of trees and shrubs was negligible in experimental plots, highlighting the importance of seed supply and dispersal as ultimate determinants of recruitment. [source]