Organic fertilisation enhances generalist predators and suppresses aphid growth in the absence of specialist predators

AbstractMost caecilians are thought to be generalist predators of soil ecosystem engineers (earthworms, termites and ants), but it has been suggested that members of the East African genus Boulengerula are specialist predators. Surprisingly, in the only detailed study of diet of any Boulengerula, the authors speculated that B. taitanus is partly detritivorous, based on the large amount of organic matter found in the alimentary canal. Here we test the conflicting hypotheses that B.taitanus is a termitivore or detritivore, using the stomach and gut contents of 47 specimens collected in the Taita Hills, Kenya. Termites and earthworms contribute most significantly to diet by number and mass, respectively. These constitute the major dietary items, together with dipteran larvae and other soil macrofauna. Contents of the intestine are mostly soil and organic matter originating from prey items. The mass content of the intestines averages 69% of total gut contents, and is significantly greater than identifiable stomach contents. The null hypotheses that B. taitanus is a generalist and a predator are not rejected.

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Specialist Predators, Generalist Predators, and the Microtine Rodent Cycle

Journal of Animal Ecology ◽

10.2307/5465 ◽

1991 ◽

Vol 60 (1) ◽

pp. 353 ◽

Cited By ~ 453

Author(s):

Ilkka Hanski ◽

Lennart Hansson ◽

Heikki Henttonen

Keyword(s):

Generalist Predators ◽

Microtine Rodent ◽

Specialist Predators

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Unstable predator–prey dynamics permits the coexistence of generalist and specialist predators, and the maintenance of partial preferences

Israel Journal of Ecology and Evolution ◽

10.1080/15659801.2013.823749 ◽

2013 ◽

Vol 59 (1) ◽

pp. 27-36 ◽

Cited By ~ 1

Author(s):

Robert D. Holt ◽

Manojit Roy ◽

Michael Barfield

Keyword(s):

Dynamic Instability ◽

Poor Quality ◽

Generalist Predators ◽

Functional Responses ◽

High Quality ◽

Dietary Specialization ◽

Predator Prey ◽

Predator Prey Model ◽

Partial Preference ◽

Specialist Predators

Saturating functional responses are a unifying principle in ecology, influencing processes at organizational levels from dietary specialization in individuals, to population instability, to community-level indirect interactions among alternative prey. These effects are interrelated. We explore a predator–prey model and demonstrate that unstable dynamics promote coexistence of specialist and generalist predators, when the specialist attacks only high-quality prey, and the generalist attacks high- and low-quality prey (that alone cannot maintain the predator). Coexisting specialist and generalist predators are vulnerable to invasion and replacement by predators with fixed partial preferences. The evolutionarily stable partial preference increases with increasing dynamic instability, but typically declines with increasing abundance of the low-quality prey. Coexisting specialist and generalist consumers, or partial preferences, typically reduce the potential for poor-quality prey to indirectly benefit high-quality prey. We suggest that dynamic instability may also contribute to the evolutionary maintenance of seemingly maladaptive oviposition choices by insect parasitoids.

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What Explains Forest Grouse Mortality: Predation Impacts of Raptors, Vole Abundance, or Weather Conditions?

International Journal of Ecology ◽

10.1155/2012/375260 ◽

2012 ◽

Vol 2012 ◽

pp. 1-10 ◽

Cited By ~ 8

Author(s):

Risto Tornberg ◽

Vitali Reif ◽

Erkki Korpimäki

Keyword(s):

Linear Response ◽

Weather Conditions ◽

Generalist Predators ◽

Black Grouse ◽

Main Prey ◽

Density Dependent ◽

Survival Pattern ◽

Kill Rate ◽

Specialist Predators ◽

Predation Rates

We investigated predation rates of black grouse chicks during 1985–2007 in two localities in western Finland in light of three predation hypothesis: The Alternative Prey Hypothesis (APH) stating that vole-eating generalist predators cause a collapse in grouse reproduction after voles’ decline, the Main Prey Hypothesis (MPH), where grouse specialised predators by a lagged response cause an inversely density dependent predation for prey and the Predation Facilitation Hypothesis (PFH), where generalist and specialist predators act in concert. We also studied the effect of weather on grouse reproduction. We found that buzzard predation alone did not support APH, but did so when combined with goshawk predation. Kill rate by goshawks showed a linear response for black grouse chicks but was not density dependent. It, however, explained the losses of chicks but not their autumn density. Combined density of chicks with adults correlated with vole index in the latter study period (since 1994), thus, giving some support for APH. Weather seemed to have no effect on black grouse reproduction. Although buzzards and goshawks took, on average, only 10% of hatched grouse chicks we conclude that the among-year survival pattern of juvenile forest grouse may largely be determined by raptor predation.

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Trophic structure of macroinvertebrates in tropical pasture streams

Acta Limnologica Brasiliensia ◽

10.1590/s2179-975x0316 ◽

2016 ◽

Vol 28 (0) ◽

Cited By ~ 1

Author(s):

Bruna Neves da Silveira-Manzotti ◽

Angelo Rodrigo Manzotti ◽

Mônica Ceneviva-Bastos ◽

Lilian Casatti

Keyword(s):

Organic Matter ◽

Content Analysis ◽

Particulate Organic Matter ◽

Food Resource ◽

Tropical Streams ◽

Generalist Predators ◽

Trophic Groups ◽

Gut Content Analysis ◽

Gut Content ◽

Specialist Predators

Abstract: Aim The aim of this study was to describe the diet of stream macroinvertebrates and to determine their trophic groups. Methods Invertebrates were sampled with D nets in three pasture streams. They were identified to genus level and submitted to gut content analysis, except for fluid feeders such as hemipterans, to which diet data was obtained from the literature. Trophic groups were determined based on a similarity analysis using the Bray-Curtis similarity coefficient. Results Five trophic groups were defined: fine-detritivores (feed mostly on fine particulate organic matter - FPOM), coarse-detritivores/herbivores (feed mostly on coarse particulate organic matter - CPOM - and plant material), omnivores, specialist-predators (prey upon aquatic insects only), and generalist-predators. Ephemeroptera, Diptera (except Tanypodinae), Coleoptera, and Trichoptera (except Smicridea) were detritivores. The caddis Macronema (Trichoptera) fed exclusively on plant detritus and Tanypodinae and Smicridea were classified as omnivores. The odonate families Calopterygidae and Gomphidae were classified as specialist-predators, while Macrobrachium (Decapoda), Belostoma, and Limnocoris (Hemiptera) were generalist-predators. Conclusions The great quantity and frequency of occurrence of FPOM consumed by most taxa highlight the importance of this food resource for macroinvertebrate communities from tropical streams. Furthermore, observed variations on trophic group assignment for some taxa indicate the generalist and opportunistic nature of these aquatic invertebrates. Such findings reinforce the importance of conducting gut content analysis on macroinvertebrates to understand their role in the structure and functioning of tropical streams.

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THE POPULATION OF WHITE-BELLIED PLANTHOPPERS AND THEIR NATURAL ENEMIES: THE NEW PEST OF CORN IN LAMPUNG

JURNAL HAMA DAN PENYAKIT TUMBUHAN TROPIKA ◽

10.23960/j.hptt.11865-74 ◽

2018 ◽

Vol 18 (1) ◽

pp. 65

Author(s):

I Gede Swibawa ◽

Franciscus Xaverius Susilo ◽

Agus Muhammad Hariri ◽

Solikhin .

Keyword(s):

Population Density ◽

Natural Enemies ◽

Adult Stage ◽

Block Design ◽

Survey Method ◽

Generalist Predators ◽

Limited Information ◽

Exotic Pests ◽

Specialist Predators ◽

New Pest

The Population of White-Bellied Planthoppers and their Natural Enemies: the New Pest of Corn in Lampung. The white-bellied planthoppers (Stenocranus pasificus), hereinafter referred to as WBP, as new exotic pests in Lampung have the poten-tial to reduce corn production and threaten national food sovereignty. Therefore, population of the pest needs to be managed to prevent the outbreaks. However, there is still limited information on the bio-ecology of WBP. Thus, this research was conducted to: 1) study the population growth pattern of WBP on various corn cultivars and 2) document the natural enemies of WBP. This research was carried out from May to December 2017with a survey method on several corn fields in South Lampung and planting trial on an experimental field of Faculty of Agriculture, Universitas Lampung planted with 3 corn cultivars, i.e. Madura, P-27 and NK which were arranged in randomized complete block design with three replications. The results of the research showed: 1) there were two peaks of population density observed during plant growth. The peak of adult stage of macroptera population density occurred at 17 and 53 days after planting (dap), the highest number of leaves with oviposition mass was observed at 24 and 65 dap, while the peak of population density of nymph stage and adult stage of brachiptera occurred at 31 and 75 dap; 2) Natural enemies of WBP included 9 orders, classified as specialist predators of mirid bugs (Cyrtorhynus) and rove beetles (Paederus), and generalist predators of spiders (Araneae) and lady beetles (Coccinellidae). The population of specialist predators was fluctuated depending on WBP population, while the population of generalist predators was varied.

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Prey removal in cotton crops next to woodland reveals periodic diurnal and nocturnal invertebrate predation gradients from the crop edge by birds and bats

Scientific Reports ◽

10.1038/s41598-021-84633-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Heidi L. Kolkert ◽

Rhiannon Smith ◽

Romina Rader ◽

Nick Reid

Keyword(s):

Pest Control ◽

Open Space ◽

Optimal Foraging Theory ◽

Time Of Day ◽

Camera Traps ◽

Generalist Predators ◽

Crop Cover ◽

Foraging Preferences ◽

Experimental Feeding ◽

Natural Pest Control

AbstractFactors influencing the efficacy of insectivorous vertebrates in providing natural pest control services inside crops at increasing distances from the crop edge are poorly understood. We investigated the identity of vertebrate predators (birds and bats) and removal of sentinel prey (mealworms and beetles) from experimental feeding trays in cotton crops using prey removal trials, camera traps and observations. More prey was removed during the day than at night, but prey removal was variable at the crop edge and dependent on the month (reflecting crop growth and cover) and time of day. Overall, the predation of mealworms and beetles was 1-times and 13-times greater during the day than night, respectively, with predation on mealworms 3–5 times greater during the day than night at the crop edge compared to 95 m inside the crop. Camera traps identified many insectivorous birds and bats over crops near the feeding trays, but there was no evidence of bats or small passerines removing experimental prey. A predation gradient from the crop edge was evident, but only in some months. This corresponded to the foraging preferences of open-space generalist predators (magpies) in low crop cover versus the shrubby habitat preferred by small passerines, likely facilitating foraging away from the crop edge later in the season. Our results are in line with Optimal Foraging Theory and suggest that predators trade-off foraging behaviour with predation risk at different distances from the crop edge and levels of crop cover. Understanding the optimal farm configuration to support insectivorous bird and bat populations can assist farmers to make informed decisions regarding in-crop natural pest control and maximise the predation services provided by farm biodiversity.

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Biological Control of Pest Non-Marine Molluscs: A Pacific Perspective on Risks to Non-Target Organisms

Insects ◽

10.3390/insects12070583 ◽

2021 ◽

Vol 12 (7) ◽

pp. 583

Author(s):

Carl C. Christensen ◽

Robert H. Cowie ◽

Norine W. Yeung ◽

Kenneth A. Hayes

Keyword(s):

Biological Control ◽

Environmental Impacts ◽

Pacific Islands ◽

Generalist Predators ◽

Snail Species ◽

Marine Mollusk ◽

The Pacific ◽

History Of ◽

Ecosystem Level ◽

Scientific Framework

Classic biological control of pest non-marine mollusks has a long history of disastrous outcomes, and despite claims to the contrary, few advances have been made to ensure that contemporary biocontrol efforts targeting mollusks are safe and effective. For more than half a century, malacologists have warned of the dangers in applying practices developed in the field of insect biological control, where biocontrol agents are often highly host-specific, to the use of generalist predators and parasites against non-marine mollusk pests. Unfortunately, many of the lessons that should have been learned from these failed biocontrol programs have not been rigorously applied to contemporary efforts. Here, we briefly review the failures of past non-marine mollusk biocontrol efforts in the Pacific islands and their adverse environmental impacts that continue to reverberate across ecosystems. We highlight the fact that none of these past programs has ever been demonstrated to be effective against targeted species, and at least two (the snails Euglandina spp. and the flatworm Platydemus manokwari) are implicated in the extinction of hundreds of snail species endemic to Pacific islands. We also highlight other recent efforts, including the proposed use of sarcophagid flies and nematodes in the genus Phasmarhabditis, that clearly illustrate the false claims that past bad practices are not being repeated. We are not making the claim that biocontrol programs can never be safe and effective. Instead, we hope that in highlighting the need for robust controls, clear and measurable definitions of success, and a broader understanding of ecosystem level interactions within a rigorous scientific framework are all necessary before claims of success can be made by biocontrol advocates. Without such amendments to contemporary biocontrol programs, it will be impossible to avoid repeating the failures of non-marine mollusk biocontrol programs to date.

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Development and Interrogation of a Transcriptomic Resource for the Giant Triton Snail (Charonia tritonis)

Marine Biotechnology ◽

10.1007/s10126-021-10042-7 ◽

2021 ◽

Author(s):

AH Klein ◽

CA Motti ◽

AK Hillberg ◽

T Ventura ◽

P Thomas-Hall ◽

...

Keyword(s):

Developmental Stages ◽

Cell Signalling ◽

Natural Populations ◽

Olfactory Receptors ◽

Gill Tissue ◽

Abundant Species ◽

Population Outbreaks ◽

Coral Reef Ecosystems ◽

Specialist Predators ◽

G Protein Coupled

AbstractGastropod molluscs are among the most abundant species that inhabit coral reef ecosystems. Many are specialist predators, along with the giant triton snail Charonia tritonis (Linnaeus, 1758) whose diet consists of Acanthaster planci (crown-of-thorns starfish), a corallivore known to consume enormous quantities of reef-building coral. C. tritonis are considered vulnerable due to overexploitation, and a decline in their populations is believed to have contributed to recurring A. planci population outbreaks. Aquaculture is considered one approach that could help restore natural populations of C. tritonis and mitigate coral loss; however, numerous questions remain unanswered regarding their life cycle, including the molecular factors that regulate their reproduction and development. In this study, we have established a reference C. tritonis transcriptome derived from developmental stages (embryo and veliger) and adult tissues. This was used to identify genes associated with cell signalling, such as neuropeptides and G protein-coupled receptors (GPCRs), involved in endocrine and olfactory signalling. A comparison of developmental stages showed that several neuropeptide precursors are exclusively expressed in post-hatch veligers and functional analysis found that FFamide stimulated a significant (20.3%) increase in larval heart rate. GPCRs unique to veligers, and a diversity of rhodopsin-like GPCRs located within adult cephalic tentacles, all represent candidate olfactory receptors. In addition, the cytochrome P450 superfamily, which participates in the biosynthesis and degradation of steroid hormones and lipids, was also found to be expanded with at least 91 genes annotated, mostly in gill tissue. These findings further progress our understanding of C. tritonis with possible application in developing aquaculture methods.

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Evaluating the Impact of Two Generalist Predators on the Leafhopper Erasmoneura vulnerata Population Density

Insects ◽

10.3390/insects12040321 ◽

2021 ◽

Vol 12 (4) ◽

pp. 321

Author(s):

Stefan Cristian Prazaru ◽

Giulia Zanettin ◽

Alberto Pozzebon ◽

Paola Tirello ◽

Francesco Toffoletto ◽

...

Keyword(s):

Field Experiments ◽

Field Studies ◽

Generalist Predators ◽

Predator Species ◽

Potted Plants ◽

Naturally Occurring ◽

Orius Majusculus ◽

Limited Effectiveness ◽

Pest Outbreaks ◽

The Impact

Outbreaks of the Nearctic leafhopper Erasmoneura vulnerata represent a threat to vinegrowers in Southern Europe, in particular in North-eastern Italy. The pest outbreaks are frequent in organic vineyards because insecticides labeled for organic viticulture show limited effectiveness towards leafhoppers. On the other hand, the naturally occurring predators and parasitoids of E. vulnerata in vineyards are often not able to keep leafhopper densities at acceptable levels for vine-growers. In this study, we evaluated the potential of two generalist, commercially available predators, Chrysoperla carnea and Orius majusculus, in suppressing E. vulnerata. Laboratory and semi-field experiments were carried out to evaluate both species’ predation capacity on E. vulnerata nymphs. The experiments were conducted on grapevine leaves inside Petri dishes (laboratory) and on potted and caged grapevines (semi-field); in both experiments, the leaves or potted plants were infested with E. vulnerata nymphs prior to predator releases. Both predator species exhibited a remarkable voracity and significantly reduced leafhopper densities in laboratory and semi-field experiments. Therefore, field studies were carried out over two growing seasons in two vineyards. We released 4 O. majusculus adults and 30 C. carnea larvae per m2 of canopy. Predator releases in vineyards reduced leafhopper densities by about 30% compared to the control plots. Results obtained in this study showed that the two predators have a potential to suppress the pest density, but more research is required to define appropriate predator–prey release ratios and release timing. Studies on intraguild interactions and competition with naturally occurring predators are also suggested.

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