scholarly journals Phagotrophic Protists and Their Associates: Evidence for Preferential Grazing in an Abiotically Driven Soil Ecosystem

2021 ◽  
Vol 9 (8) ◽  
pp. 1555
Author(s):  
Andrew R. Thompson ◽  
Andrea J. Roth-Monzón ◽  
Zachary T. Aanderud ◽  
Byron J. Adams
Keyword(s):  
Species Interactions ◽  
Abiotic Factors ◽  
Wall Structure ◽  
Dry Valleys ◽  
Food Web Structure ◽  
Soil Biodiversity ◽  
Soil Food Webs ◽  
Web Structure ◽  
Starting Point ◽  
Occurrence Patterns

The complex relationship between ecosystem function and soil food web structure is governed by species interactions, many of which remain unmapped. Phagotrophic protists structure soil food webs by grazing the microbiome, yet their involvement in intraguild competition, susceptibility to predator diversity, and grazing preferences are only vaguely known. These species-dependent interactions are contextualized by adjacent biotic and abiotic processes, and thus obfuscated by typically high soil biodiversity. Such questions may be investigated in the McMurdo Dry Valleys (MDV) of Antarctica because the physical environment strongly filters biodiversity and simplifies the influence of abiotic factors. To detect the potential interactions in the MDV, we analyzed the co-occurrence among shotgun metagenome sequences for associations suggestive of intraguild competition, predation, and preferential grazing. In order to control for confounding abiotic drivers, we tested co-occurrence patterns against various climatic and edaphic factors. Non-random co-occurrence between phagotrophic protists and other soil fauna was biotically driven, but we found no support for competition or predation. However, protists predominately associated with Proteobacteria and avoided Actinobacteria, suggesting grazing preferences were modulated by bacterial cell-wall structure and growth rate. Our study provides a critical starting-point for mapping protist interactions in native soils and highlights key trends for future targeted molecular and culture-based approaches.

scholarly journals Constraints and variation in food web link-species space

2021 ◽  
Vol 17 (4) ◽  
Author(s):  
Jean P. Gibert ◽  
Daniel J. Wieczynski
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Empirical Data ◽  
Species Interactions ◽  
Fundamental Aspect ◽  
Food Web Structure ◽  
Web Structure ◽  
Scaling Relationship ◽  
The Relationship ◽  
Standing Question

Predicting food web structure in future climates is a pressing goal of ecology. These predictions may be impossible without a solid understanding of the factors that structure current food webs. The most fundamental aspect of food web structure—the relationship between the number of links and species—is still poorly understood. Some species interactions may be physically or physiologically ‘forbidden'—like consumption by non-consumer species—with possible consequences for food web structure. We show that accounting for these ‘forbidden interactions' constrains the feasible link-species space, in tight agreement with empirical data. Rather than following one particular scaling relationship, food webs are distributed throughout this space according to shared biotic and abiotic features. Our study provides new insights into the long-standing question of which factors determine this fundamental aspect of food web structure.

Modelling the interactions of soil microbes and nematodes

Nematology ◽  
2009 ◽  
Vol 11 (4) ◽  
pp. 619-629 ◽  
Author(s):  
Jouni K. Nieminen
Keyword(s):  
Dynamic Model ◽  
Material Flow ◽  
Model Performance ◽  
Food Chains ◽  
Food Web Structure ◽  
Soil Food Webs ◽  
Web Structure ◽  
Discrete Dynamic Model ◽  
Key Parameter

Abstract Six different soil food webs, assembled from a bacterium, a bacterial-feeding nematode, a fungus and a fungal-feeding nematode, were established in replicated laboratory microcosms. Glucose was supplied as the sole carbon source for the microbes. Biomasses of the organisms and the concentration of dissolved organic carbon (DOC) were measured ten times during 20 weeks. A discrete dynamic model based on the material flow between system components was fitted to the experimental data. Bacterial-based food chains were largely inactive in the absence of fungi, but mutual facilitation was observed in the systems with both fungus and bacterium. The population dynamics of a fungal-feeding nematode was adequately described by the models, but the model failed to describe DOC dynamics. The quality of fungal biomass appeared to be a key parameter in the system. Model performance was improved by letting fungal parameters vary with time and food web structure. Because fungal dynamics could not be explained by a trophic-dynamic model with rigid parameters, it is suggested that non-trophic effects of fungal-feeding nematodes on fungi may be more important in microcosms.

scholarly journals Relevance of evolutionary history for food web structure

2011 ◽  
Vol 279 (1733) ◽  
pp. 1588-1596 ◽  
Author(s):  
Anna Eklöf ◽  
Matthew R. Helmus ◽  
M. Moore ◽  
Stefano Allesina
Keyword(s):  
Food Web ◽  
Species Interactions ◽  
Evolutionary History ◽  
Species Traits ◽  
Interaction Networks ◽  
Food Web Structure ◽  
Feeding Mode ◽  
Closely Related Species ◽  
Marginal Likelihoods ◽  
Web Structure

Explaining the structure of ecosystems is one of the great challenges of ecology. Simple models for food web structure aim at disentangling the complexity of ecological interaction networks and detect the main forces that are responsible for their shape. Trophic interactions are influenced by species traits, which in turn are largely determined by evolutionary history. Closely related species are more likely to share similar traits, such as body size, feeding mode and habitat preference than distant ones. Here, we present a theoretical framework for analysing whether evolutionary history—represented by taxonomic classification—provides valuable information on food web structure. In doing so, we measure which taxonomic ranks better explain species interactions. Our analysis is based on partitioning of the species into taxonomic units. For each partition, we compute the likelihood that a probabilistic model for food web structure reproduces the data using this information. We find that taxonomic partitions produce significantly higher likelihoods than expected at random. Marginal likelihoods (Bayes factors) are used to perform model selection among taxonomic ranks. We show that food webs are best explained by the coarser taxonomic ranks (kingdom to class). Our methods provide a way to explicitly include evolutionary history in models for food web structure.

Food Webs and Ecosystems: Linking Species Interactions to the Carbon Cycle

2020 ◽  
Vol 51 (1) ◽  
pp. 271-295
Author(s):  
Oswald J. Schmitz ◽  
Shawn J. Leroux
Keyword(s):  
Carbon Cycle ◽  
Food Webs ◽  
Carbon Cycling ◽  
Functional Traits ◽  
Species Interactions ◽  
Functional Integration ◽  
Food Web Structure ◽  
Carbon Modeling ◽  
Web Structure ◽  
Quantitative Synthesis

All species within ecosystems contribute to regulating carbon cycling because of their functional integration into food webs. Yet carbon modeling and accounting still assumes that only plants, microbes, and invertebrate decomposer species are relevant to the carbon cycle. Our multifaceted review develops a case for considering a wider range of species, especially herbivorous and carnivorous wild animals. Animal control over carbon cycling is shaped by the animals’ stoichiometric needs and functional traits in relation to the stoichiometry and functional traits of their resources. Quantitative synthesis reveals that failing to consider these mechanisms can lead to serious inaccuracies in the carbon budget. Newer carbon-cycle models that consider food-web structure based on organismal functional traits and stoichiometry can offer mechanistically informed predictions about the magnitudes of animal effects that will help guide new empirical research aimed at developing a coherent understanding of the interactions and importance of all species within food webs.

scholarly journals Effect of a temperature gradient on Sphagnum fallax and its associated living microbial communities: a study under controlled conditions

2011 ◽  
Vol 57 (3) ◽  
pp. 226-235 ◽  
Author(s):  
Vincent E.J. Jassey ◽  
Daniel Gilbert ◽  
Philippe Binet ◽  
Marie-Laure Toussaint ◽  
Geneviève Chiapusio
Keyword(s):  
Climate Change ◽  
Temperature Gradient ◽  
Microbial Communities ◽  
Indirect Effects ◽  
Abiotic Factors ◽  
Testate Amoebae ◽  
Trophic Relationships ◽  
Total Biomass ◽  
Food Web Structure ◽  
Web Structure

Microbial communities living in Sphagnum are known to constitute early indicators of ecosystem disturbances, but little is known about their response (including their trophic relationships) to climate change. A microcosm experiment was designed to test the effects of a temperature gradient (15, 20, and 25 °C) on microbial communities including different trophic groups (primary producers, decomposers, and unicellular predators) in Sphagnum segments (0–3 cm and 3–6 cm of the capitulum). Relationships between microbial communities and abiotic factors (pH, conductivity, temperature, and polyphenols) were also studied. The density and the biomass of testate amoebae in Sphagnum upper segments increased and their community structure changed in heated treatments. The biomass of testate amoebae was linked to the biomass of bacteria and to the total biomass of other groups added and, thus, suggests that indirect effects on the food web structure occurred. Redundancy analysis revealed that microbial assemblages differed strongly in Sphagnum upper segments along a temperature gradient in relation to abiotic factors. The sensitivity of these assemblages made them interesting indicators of climate change. Phenolic compounds represented an important explicative factor in microbial assemblages and outlined the potential direct and (or) indirect effects of phenolics on microbial communities.

scholarly journals Thermal preference influences depth use but not biomass of predatory fishes in response to lake morphometry

2019 ◽  
Author(s):  
Timothy J. Bartley ◽  
Matthew M. Guzzo ◽  
Kevin Cazelles ◽  
Alex Verville ◽  
Bailey C. McMeans ◽  
...  
Keyword(s):  
Food Web ◽  
Abiotic Factors ◽  
Thermal Preference ◽  
Lake Morphometry ◽  
Top Predator ◽  
Food Web Structure ◽  
Web Structure ◽  
Top Predators ◽  
Thermal Preferences ◽  
Depth Use

ABSTRACTTop predators’ responses to environmental conditions shape food web architecture and influence ecosystem structure and stability. Yet the impacts of fundamental properties like ecosystem size and morphometry on top predators’ behaviour are poorly understood. We examined how lake morphometry impacts the behaviour (inferred by depth use) of three key fish top predators—the cold-adapted lake trout, the cool-adapted walleye, and the warm-adapted smallmouth bass— which can each strongly impact local food web structure. We used catch-per-unit-effort data from nearly 500 boreal lakes of Ontario, Canada to evaluate the role of thermal preference in dictating mean depth of capture and biomass index in response to lake morphometry. We found evidence that thermal preferences influence how species’ depth use and biomass changed with lake size, proportion of littoral area, and maximum lake depth, although we found no relationship with lake shape. However, found no strong evidence that lake morphology influences these species’ biomasses, despite theory that predicts such a relationship. Our results suggest that some aspects of lake morphometry can alter habitat accessibility and productivity in ways that influence the behaviour and biomass of these top predator species depending on their thermal preferences. Our results have implications for how lake food webs expand and contract with lake morphometry and other key abiotic factors. We argue that several key abiotic factors likely drive top predator depth use in ways that may shape local food web structure and play an important role in determining the ultimate fate of ecosystems with environmental change.

scholarly journals How anthropogenic shifts in plant community composition alter soil food webs

F1000Research ◽  
2018 ◽  
Vol 7 ◽  
pp. 4 ◽  
Author(s):  
Paul Kardol ◽  
Jonathan R. De Long
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Plant Community ◽  
Plant Communities ◽  
Ecosystem Functions ◽  
Plant Community Composition ◽  
Soil Food Web ◽  
Food Web Structure ◽  
Soil Food Webs ◽  
Web Structure

There are great concerns about the impacts of soil biodiversity loss on ecosystem functions and services such as nutrient cycling, food production, and carbon storage. A diverse community of soil organisms that together comprise a complex food web mediates such ecosystem functions and services. Recent advances have shed light on the key drivers of soil food web structure, but a conceptual integration is lacking. Here, we explore how human-induced changes in plant community composition influence soil food webs. We present a framework describing the mechanistic underpinnings of how shifts in plant litter and root traits and microclimatic variables impact on the diversity, structure, and function of the soil food web. We then illustrate our framework by discussing how shifts in plant communities resulting from land-use change, climatic change, and species invasions affect soil food web structure and functioning. We argue that unravelling the mechanistic links between plant community trait composition and soil food webs is essential to understanding the cascading effects of anthropogenic shifts in plant communities on ecosystem functions and services.

Vegetation structure of tundra and taiga on the map of the natural vegetation of Europe

2007 ◽  
pp. 13-22 ◽  
Author(s):  
T. K. Yurkovskaya
Keyword(s):  
Vegetation Cover ◽  
Abiotic Factors ◽  
Self Regulation ◽  
Space Structure ◽  
Middle Taiga ◽  
Russian Plain ◽  
Forest Communities ◽  
The North ◽  
Tundra Vegetation ◽  
Starting Point

I have focused only on some features of structure in the taiga vegetation cover. In conclusion I would like to tell some words about the causes of complicated space structure of the taiga and tundra vegetation cover. The causes of latitudinal differentiation are climatic undoubtedly, but heterogeneity of vegetation cover within the limits of tundra and taiga subzones is accounted for different factors. In tundra abiogenic factors prevail, first of all the permafrost processes. That is the reason why tundra vegetation cover is so sensible to any disturbances and so hard regenerates after various transformations. In taiga the space structure is mostly the result of self-regulation and self- restoration of biota. The abiotic factors, certainly, play significant role, but they recede to the second plan. So we showed that in the north and middle taiga the structure of vegetation cover, during the Holocene up to present time, is determined in many respects by the increasing role of mires. Suffice it to look at the map of distribution of mires in order to estimate their role in vegetation cover of the easteuropean taiga (Yurkovskaya, 1980). So, the increase of mire area on the Russian Plain in m2/year per 1000 ha varies between 200 and 700, the average increas is ca 300—400 m2/year (Elina et all., 2000). The mires favour peniplenization and unite the separate areas of forest communities into the whole by means of forming the buffer paludificated territories (various hydrophilous variants of forest communities). But if mires, at all their stability, after destroying practically don't restore, the forests even after continuous cuttings restore their structure and composition through the series of successional stages unless an ecotope is damaged completely. Hence the space structure of taiga is the result, first of all, self development and self regulation of its vegetation cover. But, as it is known, at present time the process of destruction of natural biota has gone too far that the question arises not only about supporting its state and structure but also about the survival of the mankind itself. In this regard the vegetation map of Europe is the invaluable basis, which gives the starting point for all conservational, ecological and economical measures. But it is important to learn reading and using the map. And this is one of our actual goals.

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