Part–whole relations between food webs and the validity of local food-web descriptions

AbstractLocal food webs can be studied as the realisation of a sequence of colonising and extinction events, where a regional pool of species — called the metaweb— acts as a source for new species. Food webs are thus the result of assembly processes that are influenced by migration, habitat filtering, stochastic factors, and dynamical constraints. Therefore, we expect their structure to reflect the action of these influences.We compared the structure of empirical local food webs to (1) a metaweb, (2) randomly-constructed webs, and (3) webs resulting from an assembly model. The assembly model had no population dynamics but simply required that consumer species have at least one prey present in the local web. We compared global properties, network sub-structures—motifs— and topological roles that are node-level properties. We hypothesised that the structure of empirical food webs should differ from other webs in a way that reflected dynamical stability and other local constraints. Three data-sets were used: (1) the marine Antarctic metaweb, built using a dietary database; (2) the Weddell Sea local food web; and (3) the Potter Cove local food web.Contrary to our expectation, we found that, while most network global properties of empirical webs were different from random webs, there were almost no differences between empirical webs and those resulting from the assembly model. Further, while empirical webs showed different motif representations compared to the assembly model, these were not motifs associated with increased stability. Species’ topological roles showed differences between the metaweb and local food webs that were not explained by the assembly model, suggesting that species in empirical webs are selected by habitat or dispersal limitations.Our results suggest that there is not a strong dynamical restriction upon food web structure that operates at local scales. Instead, the structure of local webs is inherited from the metaweb with modifications imposed by local habitats.Recently, it has been found in competitive and mutualistic networks that structures that are often attributed as causes or consequences of ecological stability are probably a by-product of the assembly processes (i.e. spandrels). We extended these results to trophic networks suggesting that this could be a more general phenomenon.

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Landscape heterogeneity buffers biodiversity of simulated meta-food-webs under global change through rescue and drainage effects

Nature Communications ◽

10.1038/s41467-021-24877-0 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Remo Ryser ◽

Myriam R. Hirt ◽

Johanna Häussler ◽

Dominique Gravel ◽

Ulrich Brose

Keyword(s):

Habitat Fragmentation ◽

Food Web ◽

Food Webs ◽

Landscape Heterogeneity ◽

Landscape Connectivity ◽

Biodiversity Loss ◽

Mechanistic Explanation ◽

Population Densities ◽

Rescue Effect ◽

Drainage Effect

AbstractHabitat fragmentation and eutrophication have strong impacts on biodiversity. Metacommunity research demonstrated that reduction in landscape connectivity may cause biodiversity loss in fragmented landscapes. Food-web research addressed how eutrophication can cause local biodiversity declines. However, there is very limited understanding of their cumulative impacts as they could amplify or cancel each other. Our simulations of meta-food-webs show that dispersal and trophic processes interact through two complementary mechanisms. First, the ‘rescue effect’ maintains local biodiversity by rapid recolonization after a local crash in population densities. Second, the ‘drainage effect’ stabilizes biodiversity by preventing overshooting of population densities on eutrophic patches. In complex food webs on large spatial networks of habitat patches, these effects yield systematically higher biodiversity in heterogeneous than in homogeneous landscapes. Our meta-food-web approach reveals a strong interaction between habitat fragmentation and eutrophication and provides a mechanistic explanation of how landscape heterogeneity promotes biodiversity.

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The more food webs change, the more they stay the same

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2008.0273 ◽

2009 ◽

Vol 364 (1524) ◽

pp. 1789-1801 ◽

Cited By ~ 84

Author(s):

Kevin Shear McCann ◽

Neil Rooney

Keyword(s):

Food Web ◽

Food Webs ◽

Temporal Variability ◽

Spatial And Temporal Variability ◽

Scale Invariant ◽

Food Web Structure ◽

Behavioural Responses ◽

Web Structure ◽

Food Web Ecology ◽

Food Web Theory

Here, we synthesize a number of recent empirical and theoretical papers to argue that food-web dynamics are characterized by high amounts of spatial and temporal variability and that organisms respond predictably, via behaviour, to these changing conditions. Such behavioural responses on the landscape drive a highly adaptive food-web structure in space and time. Empirical evidence suggests that underlying attributes of food webs are potentially scale-invariant such that food webs are characterized by hump-shaped trophic structures with fast and slow pathways that repeat at different resolutions within the food web. We place these empirical patterns within the context of recent food-web theory to show that adaptable food-web structure confers stability to an assemblage of interacting organisms in a variable world. Finally, we show that recent food-web analyses agree with two of the major predictions of this theory. We argue that the next major frontier in food-web theory and applied food-web ecology must consider the influence of variability on food-web structure.

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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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The use of DNA barcodes in food web construction—terrestrial and aquatic ecologists unite!

Genome ◽

10.1139/gen-2015-0229 ◽

2016 ◽

Vol 59 (9) ◽

pp. 603-628 ◽

Cited By ~ 47

Author(s):

Tomas Roslin ◽

Sanna Majaneva

Keyword(s):

Food Web ◽

Food Webs ◽

Taxonomic Resolution ◽

Dna Barcodes ◽

Food Web Structure ◽

Web Studies ◽

Web Structure ◽

Asking Questions ◽

Web Construction ◽

Interaction Webs

By depicting who eats whom, food webs offer descriptions of how groupings in nature (typically species or populations) are linked to each other. For asking questions on how food webs are built and work, we need descriptions of food webs at different levels of resolution. DNA techniques provide opportunities for highly resolved webs. In this paper, we offer an exposé of how DNA-based techniques, and DNA barcodes in particular, have recently been used to construct food web structure in both terrestrial and aquatic systems. We highlight how such techniques can be applied to simultaneously improve the taxonomic resolution of the nodes of the web (i.e., the species), and the links between them (i.e., who eats whom). We end by proposing how DNA barcodes and DNA information may allow new approaches to the construction of larger interaction webs, and overcome some hurdles to achieving adequate sample size. Most importantly, we propose that the joint adoption and development of these techniques may serve to unite approaches to food web studies in aquatic and terrestrial systems—revealing the extent to which food webs in these environments are structured similarly to or differently from each other, and how they are linked by dispersal.

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Microbial food web dynamics along a soil chronosequence of a glacier forefield

Biogeosciences ◽

10.5194/bg-8-3283-2011 ◽

2011 ◽

Vol 8 (11) ◽

pp. 3283-3294 ◽

Cited By ~ 31

Author(s):

J. Esperschütz ◽

A. Pérez-de-Mora ◽

K. Schreiner ◽

G. Welzl ◽

F. Buegger ◽

...

Keyword(s):

Food Web ◽

Microbial Communities ◽

Food Webs ◽

Litter Decomposition ◽

Developmental Stages ◽

Food Web Dynamics ◽

Glacier Forefield ◽

Microbial Food Webs ◽

And Function ◽

The 19Th Century

Abstract. Microbial food webs are critical for efficient nutrient turnover providing the basis for functional and stable ecosystems. However, the successional development of such microbial food webs and their role in "young" ecosystems is unclear. Due to a continuous glacier retreat since the middle of the 19th century, glacier forefields have expanded offering an excellent opportunity to study food web dynamics in soils at different developmental stages. In the present study, litter degradation and the corresponding C fluxes into microbial communities were investigated along the forefield of the Damma glacier (Switzerland). 13C-enriched litter of the pioneering plant Leucanthemopsis alpina (L.) Heywood was incorporated into the soil at sites that have been free from ice for approximately 10, 60, 100 and more than 700 years. The structure and function of microbial communities were identified by 13C analysis of phospholipid fatty acids (PLFA) and phospholipid ether lipids (PLEL). Results showed increasing microbial diversity and biomass, and enhanced proliferation of bacterial groups as ecosystem development progressed. Initially, litter decomposition proceeded faster at the more developed sites, but at the end of the experiment loss of litter mass was similar at all sites, once the more easily-degradable litter fraction was processed. As a result incorporation of 13C into microbial biomass was more evident during the first weeks of litter decomposition. 13C enrichments of both PLEL and PLFA biomarkers following litter incorporation were observed at all sites, suggesting similar microbial foodwebs at all stages of soil development. Nonetheless, the contribution of bacteria, especially actinomycetes to litter turnover became more pronounced as soil age increased in detriment of archaea, fungi and protozoa, more prominent in recently deglaciated terrain.

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Food-web modification in the eastern Gulf of Finland after invasion of Marenzelleria arctia (Spionidae, Polychaeta)

NeoBiota ◽

10.3897/neobiota.66.63847 ◽

2021 ◽

Vol 66 ◽

pp. 75-94

Author(s):

Sergey Golubkov ◽

Alexei Tiunov ◽

Mikhail Golubkov

Keyword(s):

Food Web ◽

Food Webs ◽

Food Chain ◽

Native Species ◽

Isotope Analysis ◽

Marine Species ◽

Trophic Levels ◽

Benthivorous Fish ◽

Neva Estuary ◽

The Baltic

The paucity of data on non-indigenous marine species is a particular challenge for understanding the ecology of invasions and prioritising conservation and research efforts in marine ecosystems. Marenzelleria spp. are amongst the most successful non-native benthic species in the Baltic Sea during recent decades. We used stable isotope analysis (SIA) to test the hypothesis that the dominance of polychaete worm Marenzelleria arctia in the zoobenthos of the Neva Estuary after its invasion in the late 2000s is related to the position of this species in the benthic food webs. The trend towards a gradual decrease in the biomass of Marenzelleria worms was observed during 2014–2020, probably due to significant negative relationships between the biomass of oligochaetes and polychaetes, both of which, according to SIA, primarily use allochthonous organic carbon for their production. The biomass of benthic crustaceans practically did not change and remained very low. The SIA showed that, in contrast to the native crustacean Monoporeia affinis, polychates are practically not consumed either by the main invertebrate predator Saduria entomon, which preys on M. affinis, oligochaetes and larvae of chironomids or by benthivorous fish that prefer native benthic crustaceans. A hypothetical model for the position and functional role of M. arctia in the bottom food web is presented and discussed. According the model, the invasion of M. arctia has created an offshoot food chain in the Estuary food webs. The former dominant food webs, associated with native crustaceans, are now poorly developed. The lack of top-down control obviously contributes to the significant development of the Marenzelleria food chain, which, unlike native food chains, does not provide energy transfer from autochthonous and allochthonous organic matter to the upper trophic levels. The study showed that an alien species, without displacing native species, can significantly change the structure of food webs, creating blind offshoots of the food chain.

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Untangling the roles of parasites in food webs with generative network models

10.1101/019497 ◽

2015 ◽

Cited By ~ 1

Author(s):

Abigail Z. Jacobs ◽

Jennifer A. Dunne ◽

Cristopher Moore ◽

Aaron Clauset

Keyword(s):

Food Web ◽

Food Webs ◽

Statistical Physics ◽

Network Models ◽

Food Web Structure ◽

Free Living ◽

Web Structure ◽

Living Species ◽

Parasitic Interactions ◽

The Impact

Food webs represent the set of consumer-resource interactions among a set of species that co-occur in a habitat, but most food web studies have omitted parasites and their interactions. Recent studies have provided conflicting evidence on whether including parasites changes food web structure, with some suggesting that parasitic interactions are structurally distinct from those among free-living species while others claim the opposite. Here, we describe a principled method for understanding food web structure that combines an efficient optimization algorithm from statistical physics called parallel tempering with a probabilistic generalization of the empirically well-supported food web niche model. This generative model approach allows us to rigorously estimate the degree to which interactions that involve parasites are statistically distinguishable from interactions among free-living species, whether parasite niches behave similarly to free-living niches, and the degree to which existing hypotheses about food web structure are naturally recovered. We apply this method to the well-studied Flensburg Fjord food web and show that while predation on parasites, concomitant predation of parasites, and parasitic intraguild trophic interactions are largely indistinguishable from free-living predation interactions, parasite-host interactions are different. These results provide a powerful new tool for evaluating the impact of classes of species and interactions on food web structure to shed new light on the roles of parasites in food webs.

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Mesoscale variations in the assemblage structure and trophodynamics of mesozooplankton communities of the Adriatic basin (Mediterranean Sea)

10.5194/bg-2021-240 ◽

2021 ◽

Author(s):

Emanuela Fanelli ◽

Samuele Menicucci ◽

Sara Malavolti ◽

Andrea De Felice ◽

Iole Leonori

Keyword(s):

Food Web ◽

Food Webs ◽

Mediterranean Sea ◽

Environmental Variables ◽

Complex Structure ◽

Assemblage Structure ◽

Trophic Levels ◽

Ecosystem Functions ◽

Food Web Structure ◽

Adriatic Basin

Abstract. Zooplankton are critical to the functioning of ocean food webs because of their utter abundance and vital ecosystem roles. Zooplankton communities are highly diverse and thus perform a variety of ecosystem functions, thus changes in their community or food web structure may provide evidence of ecosystem alteration. Assemblage structure and trophodynamics of mesozooplantkon communities were examined across the Adriatic basin, the northernmost and most productive basin of the Mediterranean Sea. Samples were collected in June–July 2019 along coast-offshore transects covering the whole western Adriatic side, consistently environmental variables were also recorded. Results showed a clear separation between samples from the northern-central Adriatic and the southern ones, with a further segregation, although less clear, of inshore vs. off-shore stations, the latter mostly dominated in the central and southern stations by gelatinous plankton. Such patterns were mainly driven by chlorophyll-a concentration (as a proxy of primary production) for northern-central stations, i.e. closer to the Po river input, and by temperature and salinity, for southern ones, with the DistLM model explaining 46 % of total variance. The analysis of stable isotopes of nitrogen and carbon allowed to identify a complex food web characterized by 3 trophic levels from herbivores to carnivores, passing through the mixed feeding behavior of omnivores, shifting from phytoplankton/detritus ingestion to microzooplankton. Trophic structure also spatially varied according to sub-area, with the northern-central sub-areas differing from each other and from the southern stations. Our results highlighted the importance of environmental variables as drivers of zooplanktonic communities and the complex structure of their food webs. Disentangling and considering such complexity is crucial to generate realistic predictions on the functioning of aquatic ecosystems, especially in high productive and, at the same time, overexploited area such as the Adriatic Sea.

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On the centrality and uniqueness of species from the network perspective

Biology Letters ◽

10.1098/rsbl.2011.1167 ◽

2012 ◽

Vol 8 (4) ◽

pp. 570-573 ◽

Cited By ~ 25

Author(s):

Shu-Mei Lai ◽

Wei-Chung Liu ◽

Ferenc Jordán

Keyword(s):

Food Web ◽

Food Webs ◽

Ecosystem Functions ◽

Prince William Sound ◽

Important Species ◽

Network Position ◽

Central Node ◽

Species Importance

Identifying important species for maintaining ecosystem functions is a challenge in ecology. Since species are components of food webs, one way to conceptualize and quantify species importance is from a network perspective. The importance of a species can be quantified by measuring the centrality of its position in a food web, because a central node may have greater influence on others in the network. A species may also be important because it has a unique network position, such that its loss cannot be easily compensated. Therefore, for a food web to be robust, we hypothesize that central species must be functionally redundant in terms of their network position. In this paper, we test our hypothesis by analysing the Prince William Sound ecosystem. We found that species centrality and uniqueness are negatively correlated, and such an observation is also carried over to other food webs.

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