scholarly journals Plankton food-webs: to what extent can they be simplified?

2016 ◽  
Vol 7 (1) ◽  
Author(s):  
Domenico D'Alelio ◽  
Marina Montresor ◽  
Maria Grazia Mazzocchi ◽  
Francesca Margiotta ◽  
Diana Sarno ◽  
...  
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Biological Diversity ◽  
Relative Weight ◽  
Aquatic Systems ◽  
Taxonomic Resolution ◽  
Research Station ◽  
Vital Rates ◽  
Trophic Links ◽  
Plankton Models

<p class="p1">Plankton is a hugely diverse community including both unicellular and multicellular organisms, whose individual dimensions span over seven orders of magnitude. Plankton is a fundamental part of biogeochemical cycles and food-webs in aquatic systems. While knowledge has progressively accumulated at the level of single species and single trophic processes, the overwhelming biological diversity of plankton interactions is insufficiently known and a coherent and unifying trophic framework is virtually lacking. We performed an extensive review of the plankton literature to provide a compilation of data suitable for implementing food-web models including plankton trophic processes at high taxonomic resolution. We identified the components of the plankton community at the Long Term Ecological Research Station MareChiara in the Gulf of Naples. These components represented the sixty-three nodes of a plankton food-web. To each node we attributed biomass and vital rates, <em><span class="s1">i.e. </span></em>production, consumption, assimilation rates and ratio between autotrophy and heterotrophy in mixotrophic protists. Biomasses and rates values were defined for two opposite system’s conditions; relatively eutrophic and oligotrophic states. We finally identified 817 possible trophic links within the web and provided each of them with a relative weight, in order to define a diet-matrix, valid for both trophic states, which included all consumers, fromn anoflagellates to carnivorous plankton. Vital rates for plankton resulted, as expected, very wide; this strongly contrasts with the narrow ranges considered in plankton system models implemented so far. Moreover, the amount and variety of trophic links highlighted by our review is largely excluded by state-of-the-art biogeochemical and food-web models for aquatic systems. Plankton models could potentially benefit from the integration of the trophic diversity outlined in this paper: first, by using more realistic rates; second, by better defining trophic roles of consumers in the planktonic web. We suggest that most trophic habits present in planktonic organisms must be contemplated in new generation plankton models.</p>

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

Genome ◽  
2016 ◽  
Vol 59 (9) ◽  
pp. 603-628 ◽  
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.

Resolving Food-Web Structure

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.

FOOD WEBS WITH PREDATOR INTERFERENCE

1995 ◽  
Vol 03 (02) ◽  
pp. 323-330 ◽  
Author(s):  
JERZY MICHALSKI ◽  
ROGER ARDITI
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Feeding Rate ◽  
Food Preferences ◽  
External Perturbation ◽  
Food Web Structure ◽  
Web Structure ◽  
Trophic Links ◽  
Predator Interference ◽  
Species Abundances

Interfering predators have a feeding rate (functional response) which is a decreasing function of their abundance. We propose equations that describe the dynamics of an arbitrary food web with predator interference and study their consequences. In particular we show that, due to interference, some of the trophic links do not effectively exist. Their presence (or absence) depends on the interplay of competition efficiencies and food preferences as well as on species abundances. As a consequence, the effective structure of a food web may vary with time and from one place to another (as competition efficiencies and food preferences vary with seasons and from one place to another) as well as due to an external perturbation (as abundances change). The simplification of the food web structure due to predator interference allows qualitative predictions concerning the response of a food web to an external perturbation.

scholarly journals Trophic redundancy reduces vulnerability to extinction cascades

2018 ◽  
Vol 115 (10) ◽  
pp. 2419-2424 ◽  
Author(s):  
Dirk Sanders ◽  
Elisa Thébault ◽  
Rachel Kehoe ◽  
F. J. Frank van Veen
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Parasitoid Wasp ◽  
Biodiversity Loss ◽  
Species Loss ◽  
Ecological Interactions ◽  
Insect Communities ◽  
Extinction Rates ◽  
Trophic Links ◽  
Current Species

Current species extinction rates are at unprecedentedly high levels. While human activities can be the direct cause of some extinctions, it is becoming increasingly clear that species extinctions themselves can be the cause of further extinctions, since species affect each other through the network of ecological interactions among them. There is concern that the simplification of ecosystems, due to the loss of species and ecological interactions, increases their vulnerability to such secondary extinctions. It is predicted that more complex food webs will be less vulnerable to secondary extinctions due to greater trophic redundancy that can buffer against the effects of species loss. Here, we demonstrate in a field experiment with replicated plant-insect communities, that the probability of secondary extinctions is indeed smaller in food webs that include trophic redundancy. Harvesting one species of parasitoid wasp led to secondary extinctions of other, indirectly linked, species at the same trophic level. This effect was markedly stronger in simple communities than for the same species within a more complex food web. We show that this is due to functional redundancy in the more complex food webs and confirm this mechanism with a food web simulation model by highlighting the importance of the presence and strength of trophic links providing redundancy to those links that were lost. Our results demonstrate that biodiversity loss, leading to a reduction in redundant interactions, can increase the vulnerability of ecosystems to secondary extinctions, which, when they occur, can then lead to further simplification and run-away extinction cascades.

scholarly journals Does metal pollution affect stoichiometry of soil-litter food webs?

2019 ◽  
Author(s):  
Michel Asselman ◽  
Łukasz Sobczyk ◽  
January Weiner ◽  
Stefan Scheu ◽  
Anna Rożen
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Metal Pollution ◽  
Ecological Stoichiometry ◽  
N:P Ratio ◽  
Aquatic Systems ◽  
Trophic Groups ◽  
Elemental Concentrations ◽  
Macro Elements

AbstractTo date the field of ecological stoichiometry has focused mainly on aquatic systems concentrating on macro-elements. We investigated terrestrial systems and included microelements to study the elemental transfer in the detritivorous food web. We compared food webs of six sites differing in the type and degree of metal pollution along two forest transects contaminated with copper or zinc. We measured 11 elements in litter, herbivores, detritivores, predators and omnivores. Based on elemental concentrations of elements differences between trophic groups were visualized using PCA. At all sites litter C:N, C:P, C:K and C:Na ratios were higher than in animals. Invertebrate trophic groups were significantly different from each other in C:Cu, C:Zn and C:Ca ratios. The calculated resource:consumer N:P ratio suggests that invertebrates in studied forests are N limited and not P limited. Similar patterns at all sites suggests that metal pollution at the studied intensity slightly affects the transfer of elements in the terrestrial macro-invertebrate food web.

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

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.

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

2009 ◽  
Vol 364 (1524) ◽  
pp. 1789-1801 ◽  
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.

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

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.

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

2011 ◽  
Vol 8 (11) ◽  
pp. 3283-3294 ◽  
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.

scholarly journals The Effect of Forest Fragmentation on Polistinae

Sociobiology ◽  
2019 ◽  
Vol 66 (3) ◽  
pp. 508
Author(s):  
Ederson Tadeu Bueno ◽  
Marcos Magalhães de Souza ◽  
Mateus Aparecido Clemente
Keyword(s):  
Food Webs ◽  
Forest Fragmentation ◽  
Natural Enemies ◽  
Natural Environment ◽  
Biological Diversity ◽  
Social Wasps ◽  
The State ◽  
Environmental Services ◽  
Flower Visitors ◽  
Semideciduous Seasonal Forest

The forest fragmentation is caused by natural or anthropic actions, which affect negatively the biota and the environmental services rendered by biological diversity. However, there is little information on the reflex of these actions in many different groups of animals, such as social wasps, which are abundant and significantly present in neotropical environments, causing a major impact in the communities they live due to their role in food webs. As their natural enemies, wasps are important in the control of agricultural plagues; in the natural environment, they are nectar collectors, frequent flower visitors, and potential pollinators of many species of plants. These factors justify studies which would evaluate in what way the forest fragmentation acts on these insects biodiversity. This study was carried out in four fragments, each of a different size, located in the municipalities of Inconfidentes and Ouro Fino, in the south of the state of Minas Gerais (Brazil), where the phytophysiognomy is the Montane Semideciduous Seasonal Forest. The research was carried out between December 2016 and March 2018, with the same sampling collection for each fragment, totalizing 104 sampling days. In total, 28 species and 51 colonies were recorded in the four areas and a greater richness for the greatest fragment (F4). The conclusion reached was that the size and heterogeneity of the fragment have an important role in maintaining the richness of social wasps. 

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