Top-down limitation of mesopredators by avian top predators: a call for research on cascading effects at the community and ecosystem scale

AbstractCascading effects of high trophic levels onto lower trophic levels have been documented in many ecosystems. Some studies also show evidence of extended trophic cascades, in which guilds dependent on lower trophic levels, but uninvolved in the trophic cascade themselves, are affected by the trophic cascade due to their dependence on lower trophic levels. Top-down effects of large mammals on plants could lead to a variety of extended trophic cascades on the many guilds dependent on plants, such as pollinators. In this study, floral-visitor and floral abundances and assemblages were quantified within a series of 1-ha manipulations of large-mammalian herbivore density in an African savanna. Top-down effects of large mammals on the composition of flowers available for floral visitors are first shown, using regressions of herbivore activity on metrics of floral and floral-visitor assemblages. An extended trophic cascade is also shown: the floral assemblage further altered the assemblage of floral visitors, according to a variety of approaches, including a structural equation modelling approach (model with an extended trophic cascade was supported over a model without, AICc weight = 0.984). Our study provides support for extended trophic cascades affecting floral visitors, suggesting that trophic cascades can have impacts throughout entire communities.

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Loss of top-down biotic interactions changes the relative benefits for obligate mutualists

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2018.2501 ◽

2019 ◽

Vol 286 (1897) ◽

pp. 20182501 ◽

Cited By ~ 7

Author(s):

Rong Wang ◽

Xiao-Yong Chen ◽

Yan Chen ◽

Gang Wang ◽

Derek W. Dunn ◽

...

Keyword(s):

Biotic Interactions ◽

Trophic Levels ◽

Fig Wasp ◽

Negative Effects ◽

Top Down ◽

Top Predators ◽

Natural Range ◽

Obligate Mutualism ◽

The Stability ◽

Food Web Complexity

The collapse of mutualisms owing to anthropogenic changes is contributing to losses of biodiversity. Top predators can regulate biotic interactions between species at lower trophic levels and may contribute to the stability of such mutualisms, but they are particularly likely to be lost after disturbance of communities. We focused on the mutualism between the fig tree Ficus microcarpa and its host-specific pollinator fig wasp and compared the benefits accrued by the mutualists in natural and translocated areas of distribution. Parasitoids of the pollinator were rare or absent outside the natural range of the mutualists, where the relative benefits the mutualists gained from their interaction were changed significantly away from the plant's natural range owing to reduced seed production rather than increased numbers of pollinator offspring. Furthermore, in the absence of the negative effects of its parasitoids, we detected an oviposition range expansion by the pollinator, with the use of a wider range of ovules that could otherwise have generated seeds. Loss of top-down control has therefore resulted in a change in the balance of reciprocal benefits that underpins this obligate mutualism, emphasizing the value of maintaining food web complexity in the Anthropocene.

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Predator Politics

SAGE Open ◽

10.1177/2158244016679210 ◽

2017 ◽

Vol 7 (1) ◽

pp. 215824401667921

Author(s):

Mary Louisa Cappelli

Keyword(s):

Political Ecology ◽

Cultural Production ◽

Environmental Sustainability ◽

Ecological Diversity ◽

Ecological Stability ◽

Cascading Effects ◽

Edward Abbey ◽

Barbara Kingsolver ◽

Political Processes ◽

Top Predators

Edward Abbey’s Desert Solitaire and Barbara Kingsolver’s Prodigal Summer urges readers to see coyotes as crucial members of the natural community whose predation is essential for the maintenance of biodiversity and ecological stability. Their cultural production provides a human story of ecocritical engagement for understanding the cascading effects of removing top predators from their ecosystems. By envisioning biocentric possibilities within place-based and scientific contexts, Edward Abbey and Barbara Kingsolver share a common theme of political ecology: political processes shape ecological conditions. A close reading of Edward Abbey’s Desert Solitaire and Barbara Kingsolver’s Prodigal Summer provides a literary entryway to connect research, arguments, and discourse across disciplines tasking readers to engage in political discussions of environmental sustainability and to consider viable solutions to preserve the ecological diversity of our predator populations and ecosystems.

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Fungal plant endosymbionts alter life history and reproductive success of aphid predators

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2005.3442 ◽

2006 ◽

Vol 273 (1591) ◽

pp. 1301-1306 ◽

Cited By ~ 54

Author(s):

Claudio de Sassi ◽

Christine B Müller ◽

Jochen Krauss

Keyword(s):

Rhopalosiphum Padi ◽

Coccinella Septempunctata ◽

Fungal Endophyte ◽

Cereal Aphids ◽

Negative Effects ◽

Cascading Effects ◽

Top Predators ◽

Significant Damage ◽

Aphid Predators ◽

Toxic Alkaloids

Endosymbionts occur in most plant species and may affect interactions among herbivores and their predators through the production of toxic alkaloids. Here, we ask whether effects of mycotoxins produced by the symbiosis of the fungal endophyte Neotyphodium lolii and the grass Lolium perenne are transmitted to the aphidophagous ladybird Coccinella septempunctata when feeding on cereal aphids Rhopalosiphum padi on infected plants. The larval development of coccinellids was extended, while their survival was reduced when feeding exclusively on aphids from infected plants. Ladybirds developing on aphids from infected plants showed reduced fecundity and impaired reproductive performance. Body size and symmetries of ladybird adults were not affected by the endophytes. Consistently strong, negative effects of endophytes on the lifetime performance of ladybirds indicates that mycotoxins are transmitted along food chains, causing significant damage for top predators. Such cascading effects will influence the population dynamics of aphid predators in the long term and could feedback to the primary plant producers.

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Interpreting variation in fish-based food web indicators: the importance of “bottom-up limitation” and “top-down control” processes

ICES Journal of Marine Science ◽

10.1093/icesjms/fst137 ◽

2013 ◽

Vol 71 (2) ◽

pp. 406-416 ◽

Cited By ~ 6

Author(s):

T. O. M. Reilly ◽

H. M. Fraser ◽

R. J. Fryer ◽

J. Clarke ◽

S. P. R. Greenstreet

Keyword(s):

Food Web ◽

Food Webs ◽

Trophic Levels ◽

Top Down ◽

Bottom Up ◽

Control Processes ◽

Top Predators ◽

Environmental Status ◽

Fish Predators ◽

Firth Of Forth

Abstract Reilly, T. O. M., Fraser, H. M., Fryer, R. J., Clarke, J., and Greenstreet, S. P. R. 2014. Interpreting variation in fish-based food web indicators: the importance of “bottom-up limitation” and “top-down control” processes. – ICES Journal of Marine Science, 71: 406–416. Proposed indicators for the Marine Strategy Framework Directive (MSFD) food webs Descriptor focus on structural elements of food webs, and in particular on the abundance and productivity of top predators. However, the inferences that can be drawn from such indicators depend on whether or not the predators are “bottom-up limited” by the availability of their prey. Many seabird populations appear to be “bottom-up limited” so that variation in their reproductive success and/or abundance reflects changes in lower trophic levels. Here we find that gadoid fish predators off the Firth of Forth, southeast Scotland, do not appear to be “bottom-up limited” by the biomass of their main prey, 0-group sandeels; gadoid biomass and feeding performance was independent of sandeel biomass. Variability in food web indicators based on these gadoid predators seems to impart little insight into underlying processes occurring at lower trophic levels in the local food web. The implications of this in terms of how the currently proposed MSFD food web indicators should be used and interpreted are considered, and the ramifications in terms of setting targets representing good environmental status for both fish and seabird communities are discussed.

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Herbivore release through cascading risk effects

Biology Letters ◽

10.1098/rsbl.2009.0436 ◽

2009 ◽

Vol 5 (6) ◽

pp. 773-776 ◽

Cited By ~ 27

Author(s):

Martin H. Schmidt-Entling ◽

Eva Siegenthaler

Keyword(s):

Field Experiment ◽

Predation Risk ◽

Top Down ◽

Wolf Spiders ◽

Risk Effects ◽

Mediated Effects ◽

Top Predators ◽

Inverse Pattern

Predators influence prey through consumption, and through trait-mediated effects such as emigration in response to predation risk (risk effects). We studied top-down effects of (sub-) adult wolf spiders (Lycosidae) on arthropods in a meadow. We compared risk effects with the overall top-down effect (including consumption) by gluing the chelicers of wolf spiders to prevent them from killing the prey. In a field experiment, we created three treatments that included either: (i) intact (‘predation’) wolf spiders; (ii) wolf spiders with glued chelicers (‘risk spiders’); or (iii) no (sub-) adult wolf spiders. Young wolf spiders were reduced by their (sub-) adult congeners. Densities of sheetweb spiders (Linyphiidae), a known intraguild prey of wolf spiders, were equally reduced by the presence of risk and predation wolf spiders. Plant- and leafhoppers (Auchenorrhyncha) showed the inverse pattern of higher densities in the presence of both risk and predation wolf spiders. We conclude that (sub-) adult wolf spiders acted as top predators, which reduced densities of intermediate predators and thereby enhanced herbivores. Complementary to earlier studies that found trait-mediated herbivore suppression, our results demonstrate that herbivores can be enhanced through cascading risk effects by top predators.

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Business as usual leads to underperformance in coastal restoration

10.1093/oso/9780198808978.003.0027 ◽

2017 ◽

Author(s):

Brian R. Silliman ◽

Brent B. Hughes ◽

Y. Stacy Zhang ◽

Qiang He

Keyword(s):

Species Interactions ◽

Coastal Wetland ◽

Top Down ◽

Positive Interaction ◽

Marsh Restoration ◽

Coastal Restoration ◽

Top Predators ◽

The Face ◽

Conservation Projects ◽

Business As Usual

This chapter shows that coastal wetland projects are underperforming because of confirmation bias. Despite two decades of work showing that top-down control can be essential to marsh restoration, the potential role of top predators is typically ignored by those responsible for restoring or maintaining marshes. Similarly ignored are experiments that indicate positive interaction between marsh plants and can enhance the pace and success of restoration. By planting marsh plants at higher densities, marsh restoration success can double, and seagrass restoration can succeed in the face of increasing drought and eutrophication effects. Continued failure to integrate top-down control and facilitative species interactions into coastal restoration designs will result in widespread underperformance of wetland conservation projects and unrealized generation of important ecosystem services.

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Cascading effects of larval Crucian carp introduction on phytoplankton and microbial communities in a paddy field: top-down and bottom-up controls

Ecological Research ◽

10.1007/s11284-011-0820-9 ◽

2011 ◽

Vol 26 (3) ◽

pp. 615-626 ◽

Cited By ~ 8

Author(s):

Yoko Nishimura ◽

Taisuke Ohtsuka ◽

Kohei Yoshiyama ◽

Daisuke Nakai ◽

Fujiyoshi Shibahara ◽

...

Keyword(s):

Microbial Communities ◽

Paddy Field ◽

Crucian Carp ◽

Top Down ◽

Bottom Up ◽

Cascading Effects

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Interaction between top-down and bottom-up control in marine food webs

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1621037114 ◽

2017 ◽

Vol 114 (8) ◽

pp. 1952-1957 ◽

Cited By ~ 69

Author(s):

Christopher Philip Lynam ◽

Marcos Llope ◽

Christian Möllmann ◽

Pierre Helaouët ◽

Georgia Anne Bayliss-Brown ◽

...

Keyword(s):

Food Webs ◽

North Sea ◽

Time Series Data ◽

Trophic Levels ◽

Series Data ◽

Resource Exploitation ◽

Top Down ◽

Bottom Up ◽

Cascading Effects ◽

Complex Patterns

Climate change and resource exploitation have been shown to modify the importance of bottom-up and top-down forces in ecosystems. However, the resulting pattern of trophic control in complex food webs is an emergent property of the system and thus unintuitive. We develop a statistical nondeterministic model, capable of modeling complex patterns of trophic control for the heavily impacted North Sea ecosystem. The model is driven solely by fishing mortality and climatic variables and based on time-series data covering >40 y for six plankton and eight fish groups along with one bird group (>20 y). Simulations show the outstanding importance of top-down exploitation pressure for the dynamics of fish populations. Whereas fishing effects on predators indirectly altered plankton abundance, bottom-up climatic processes dominate plankton dynamics. Importantly, we show planktivorous fish to have a central role in the North Sea food web initiating complex cascading effects across and between trophic levels. Our linked model integrates bottom-up and top-down effects and is able to simulate complex long-term changes in ecosystem components under a combination of stressor scenarios. Our results suggest that in marine ecosystems, pathways for bottom-up and top-down forces are not necessarily mutually exclusive and together can lead to the emergence of complex patterns of control.

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Biogeographical region and host trophic level determine carnivore endoparasite richness in the Iberian Peninsula

Parasitology ◽

10.1017/s0031182011000345 ◽

2011 ◽

Vol 138 (6) ◽

pp. 758-765 ◽

Cited By ~ 2

Author(s):

L. M. ROSALINO ◽

M. J. SANTOS ◽

C. FERNANDES ◽

M. SANTOS-REIS

Keyword(s):

Iberian Peninsula ◽

Trophic Level ◽

Parasite Prevalence ◽

Variable Number ◽

Mean Annual Temperature ◽

Site Location ◽

Ecological Processes ◽

Cascading Effects ◽

Top Predators ◽

Biogeographical Region

SUMMARYWe address the question of whether host and/or environmental factors might affect endoparasite richness and distribution, using carnivores as a model. We reviewed studies published in international peer-reviewed journals (34 areas in the Iberian Peninsula), describing parasite prevalence and richness in carnivores, and collected information on site location, host bio-ecology, climate and detected taxa (Helminths, Protozoa andMycobacteriumspp.). Three hypotheses were tested (i) host based, (ii) environmentally based, and (iii) hybrid (combination of environmental and host). Multicollinearity reduced candidate variable number for modelling to 5: host weight, phylogenetic independent contrasts (host weight), mean annual temperature, host trophic level and biogeographical region. General Linear Mixed Modelling was used and the best model was a hybrid model that included biogeographical region and host trophic level. Results revealed that endoparasite richness is higher in Mediterranean areas, especially for the top predators. We suggest that the detected parasites may benefit from mild environmental conditions that occur in southern regions. Top predators have larger home ranges and are likely to be subjected to cascading effects throughout the food web, resulting in more infestation opportunities and potentially higher endoparasite richness. This study suggests that richness may be more affected by historical and regional processes (including climate) than by host ecological processes.

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