The trophic interactions of Octopus insularis in the food web of a pristine tropical atoll: a baseline for management and monitoring under environmental changes

AbstractTrophic interactions of cave arthropods have been understudied. We used molecular methods (NGS) to decipher the food web in the subterranean ecosystem of the Ardovská Cave (Western Carpathians, Slovakia). We collected five arthropod predators of the species Parasitus loricatus (gamasid mites), Eukoenenia spelaea (palpigrades), Quedius mesomelinus (beetles), and Porrhomma profundum and Centromerus cavernarum (both spiders) and prey belonging to several orders. Various arthropod orders were exploited as prey, and trophic interactions differed among the predators. Linear models were used to compare absolute and relative prey body sizes among the predators. Quedius exploited relatively small prey, while Eukoenenia and Parasitus fed on relatively large prey. Exploitation of eggs or cadavers is discussed. In contrast to previous studies, Eukoenenia was found to be carnivorous. A high proportion of intraguild predation was found in all predators. Intraspecific consumption (most likely cannibalism) was detected only in mites and beetles. Using Pianka’s index, the highest trophic niche overlaps were found between Porrhomma and Parasitus and between Centromerus and Eukoenenia, while the lowest niche overlap was found between Parasitus and Quedius. Contrary to what we expected, the high availability of Diptera and Isopoda as a potential prey in the studied system was not corroborated. Our work demonstrates that intraguild diet plays an important role in predators occupying subterranean ecosystems.

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Functional diversity alters the effects of a pulse perturbation on the dynamics of tritrophic food webs

10.1101/2021.03.22.436420 ◽

2021 ◽

Author(s):

Ruben Ceulemans ◽

Laurie Anne Myriam Wojcik ◽

Ursula Gaedke

Keyword(s):

Food Web ◽

Food Webs ◽

Functional Diversity ◽

Feedback Loop ◽

Environmental Changes ◽

Biodiversity Loss ◽

Trophic Levels ◽

Nutrient Pulse ◽

Trade Offs ◽

Food Web Model

Biodiversity decline causes a loss of functional diversity, which threatens ecosystems through a dangerous feedback loop: this loss may hamper ecosystems' ability to buffer environmental changes, leading to further biodiversity losses. In this context, the increasing frequency of climate and human-induced excessive loading of nutrients causes major problems in aquatic systems. Previous studies investigating how functional diversity influences the response of food webs to disturbances have mainly considered systems with at most two functionally diverse trophic levels. Here, we investigate the effects of a nutrient pulse on the resistance, resilience and elasticity of a tritrophic---and thus more realistic---plankton food web model depending on its functional diversity. We compare a non-adaptive food chain with no diversity to a highly diverse food web with three adaptive trophic levels. The species fitness differences are balanced through trade-offs between defense/growth rate for prey and selectivity/half-saturation constant for predators. We showed that the resistance, resilience and elasticity of tritrophic food webs decreased with larger perturbation sizes and depended on the state of the system when the perturbation occured. Importantly, we found that a more diverse food web was generally more resistant, resilient, and elastic. Particularly, functional diversity dampened the probability of a regime shift towards a non-desirable alternative state. In addition, despite the complex influence of the shape and type of the dynamical attractors, the basal-intermediate interaction determined the robustness against a nutrient pulse. This relationship was strongly influenced by the diversity present and the third trophic level. Overall, using a food web model of realistic complexity, this study confirms the destructive potential of the positive feedback loop between biodiversity loss and robustness, by uncovering mechanisms leading to a decrease in resistance, resilience and elasticity as functional diversity declines.

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Role of nematodes in the food web: nematodes as predator and prey.

Ecology of freshwater nematodes ◽

10.1079/9781789243635.0007 ◽

2021 ◽

pp. 216-246

Author(s):

Christoph Ptatscheck

Keyword(s):

Food Web ◽

Functional Response ◽

Trophic Interactions ◽

Individual Species ◽

Energy Fluxes ◽

Direct Observations ◽

Microcosm Studies

Abstract This chapter provides information on the role of nematodes in the food web, including their participation in matter and energy fluxes within ecosystems. It highlights that nematodes are both predators and prey for organisms ranging from protozoans to vertebrates, based on gut analyses and direct observations. Functional response experiments, microcosm studies, and enclosures/exclosures in the field can be used to investigate the intensity of these trophic interactions and their impact on individual species as well as entire communities.

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Resolving Food-Web Structure

Annual Review of Ecology Evolution and Systematics ◽

10.1146/annurev-ecolsys-110218-024908 ◽

2020 ◽

Vol 51 (1) ◽

pp. 55-80

Author(s):

Robert M. Pringle ◽

Matthew C. Hutchinson

Keyword(s):

Food Web ◽

Food Webs ◽

Trophic Interactions ◽

Sampling Methods ◽

Taxonomic Resolution ◽

Major Focus ◽

Web Data ◽

Food Web Structure ◽

Web Structure ◽

Abundant Evidence

Food webs are a major focus and organizing theme of ecology, but the data used to assemble them are deficient. Early debates over food-web data focused on taxonomic resolution and completeness, lack of which had produced spurious inferences. Recent data are widely believed to be much better and are used extensively in theoretical and meta-analytic research on network ecology. Confidence in these data rests on the assumptions ( a) that empiricists correctly identified consumers and their foods and ( b) that sampling methods were adequate to detect a near-comprehensive fraction of the trophic interactions between species. Abundant evidence indicates that these assumptions are often invalid, suggesting that most topological food-web data may remain unreliable for inferences about network structure and underlying ecological and evolutionary processes. Morphologically cryptic species are ubiquitous across taxa and regions, and many trophic interactions routinely evade detection by conventional methods. Molecular methods have diagnosed the severity of these problems and are a necessary part of the cure.

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Genetic specificity of a plant–insect food web: Implications for linking genetic variation to network complexity

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1513633113 ◽

2016 ◽

Vol 113 (8) ◽

pp. 2128-2133 ◽

Cited By ~ 37

Author(s):

Matthew A. Barbour ◽

Miguel A. Fortuna ◽

Jordi Bascompte ◽

Joshua R. Nicholson ◽

Riitta Julkunen-Tiitto ◽

...

Keyword(s):

Genetic Variation ◽

Food Web ◽

Host Plant ◽

Trophic Interactions ◽

Common Garden ◽

Ecological Networks ◽

Experimental Population ◽

Trait Variation ◽

Intraspecific Genetic Variation ◽

Food Web Complexity

Theory predicts that intraspecific genetic variation can increase the complexity of an ecological network. To date, however, we are lacking empirical knowledge of the extent to which genetic variation determines the assembly of ecological networks, as well as how the gain or loss of genetic variation will affect network structure. To address this knowledge gap, we used a common garden experiment to quantify the extent to which heritable trait variation in a host plant determines the assembly of its associated insect food web (network of trophic interactions). We then used a resampling procedure to simulate the additive effects of genetic variation on overall food-web complexity. We found that trait variation among host-plant genotypes was associated with resistance to insect herbivores, which indirectly affected interactions between herbivores and their insect parasitoids. Direct and indirect genetic effects resulted in distinct compositions of trophic interactions associated with each host-plant genotype. Moreover, our simulations suggest that food-web complexity would increase by 20% over the range of genetic variation in the experimental population of host plants. Taken together, our results indicate that intraspecific genetic variation can play a key role in structuring ecological networks, which may in turn affect network persistence.

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How habitat-modifying organisms structure the food web of two coastal ecosystems

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2015.2326 ◽

2016 ◽

Vol 283 (1826) ◽

pp. 20152326 ◽

Cited By ~ 24

Author(s):

Els M. van der Zee ◽

Christine Angelini ◽

Laura L. Govers ◽

Marjolijn J. A. Christianen ◽

Andrew H. Altieri ◽

...

Keyword(s):

Species Richness ◽

Food Web ◽

Food Webs ◽

Trophic Interactions ◽

Trophic Levels ◽

Interaction Networks ◽

Habitat Modification ◽

Seagrass Meadows ◽

Link Density ◽

Trophic Role

The diversity and structure of ecosystems has been found to depend both on trophic interactions in food webs and on other species interactions such as habitat modification and mutualism that form non-trophic interaction networks. However, quantification of the dependencies between these two main interaction networks has remained elusive. In this study, we assessed how habitat-modifying organisms affect basic food web properties by conducting in-depth empirical investigations of two ecosystems: North American temperate fringing marshes and West African tropical seagrass meadows. Results reveal that habitat-modifying species, through non-trophic facilitation rather than their trophic role, enhance species richness across multiple trophic levels, increase the number of interactions per species (link density), but decrease the realized fraction of all possible links within the food web (connectance). Compared to the trophic role of the most highly connected species, we found this non-trophic effects to be more important for species richness and of more or similar importance for link density and connectance. Our findings demonstrate that food webs can be fundamentally shaped by interactions outside the trophic network, yet intrinsic to the species participating in it. Better integration of non-trophic interactions in food web analyses may therefore strongly contribute to their explanatory and predictive capacity.

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