scholarly journals Phenotypic evolution is more constrained in simpler food webs

2019 ◽  
Author(s):  
Matthew A. Barbour ◽  
Christopher J. Greyson-Gaito ◽  
Arezoo Sootodeh ◽  
Brendan Locke ◽  
Jordi Bascompte
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Ecological Networks ◽  
Community Context ◽  
Relative Fitness ◽  
Adaptive Landscape ◽  
Phenotypic Traits ◽  
Phenotypic Evolution ◽  
Adaptive Landscapes ◽  
Food Web Complexity

AbstractGlobal change is simplifying the structure of ecological networks; however, we are currently in a poor position to predict how these simplified communities will affect the evolutionary potential of remaining populations. Theory on adaptive landscapes provides a framework for predicting how selection constrains phenotypic evolution, but often treats the community context of evolving populations as a “black box”. Here, we integrate ecological networks and adaptive landscapes to examine how changes in food-web complexity shape evolutionary constraints. We conducted a field experiment that manipulated the diversity of insect parasitoids (food-web complexity) that were able to impose selection on an insect herbivore. We then measured herbivore survival as a function of three key phenotypic traits. We found that more traits were under selection in simpler vs. more complex food webs. The adaptive landscape was more neutral in complex food webs because different parasitoid species impose different selection pressures, minimizing relative fitness differences among phenotypes. Our results suggest that phenotypic evolution becomes more constrained in simplified food webs. This indicates that the simplification of ecological communities may constrain the adaptive potential of remaining populations to future environmental change. “What escapes the eye, however, is a much more insidious kind of extinction: the extinction of ecological interactions.” Janzen (1974)

scholarly journals Oribatid mites show that soil food web complexity and close aboveground-belowground linkages emerged in the early Paleozoic

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Ina Schaefer ◽  
Tancredi Caruso
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Higher Plants ◽  
Early Paleozoic ◽  
Soil Food Web ◽  
Deep Time ◽  
Animal Group ◽  
Soil Microarthropods ◽  
Early Devonian ◽  
Food Web Complexity

Abstract The early evolution of ecosystems in Palaeozoic soils remains poorly understood because the fossil record is sparse, despite the preservation of soil microarthropods already from the Early Devonian (~410 Mya). The soil food web plays a key role in the functioning of ecosystems and its organisms currently express traits that have evolved over 400 my. Here, we conducted a phylogenetic trait analysis of a major soil animal group (Oribatida) to reveal the deep time story of the soil food web. We conclude that this group, central to the trophic structure of the soil food web, diversified in the early Paleozoic and resulted in functionally complex food webs by the late Devonian. The evolution of body size, form, and an astonishing trophic diversity demonstrates that the soil food web was as structured as current food webs already in the Devonian, facilitating the establishment of higher plants in the late Paleozoic.

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

2016 ◽  
Vol 113 (8) ◽  
pp. 2128-2133 ◽  
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.

scholarly journals Anti-predator defence and the complexity–stability relationship of food webs

2007 ◽  
Vol 274 (1618) ◽  
pp. 1617-1624 ◽  
Author(s):  
Michio Kondoh
Keyword(s):  
Species Richness ◽  
Food Web ◽  
Food Webs ◽  
Community Level ◽  
Negative Effects ◽  
Food Web Structure ◽  
Wide Range ◽  
The Stability ◽  
Food Web Complexity ◽  
Predator Defence

The mechanism for maintaining complex food webs has been a central issue in ecology because theory often predicts that complexity (higher the species richness, more the interactions) destabilizes food webs. Although it has been proposed that prey anti-predator defence may affect the stability of prey–predator dynamics, such studies assumed a limited and relatively simpler variation in the food-web structure. Here, using mathematical models, I report that food-web flexibility arising from prey anti-predator defence enhances community-level stability (community persistence and robustness) in more complex systems and even changes the complexity–stability relationship. The model analysis shows that adaptive predator-specific defence enhances community-level stability under a wide range of food-web complexity levels and topologies, while generalized defence does not. Furthermore, while increasing food-web complexity has minor or negative effects on community-level stability in the absence of defence adaptation, or in the presence of generalized defence, in the presence of predator-specific defence, the connectance–stability relationship may become unimodal. Increasing species richness, in contrast, always lowers community-level stability. The emergence of a positive connectance–stability relationship however necessitates food-web compartmentalization, high defence efficiency and low defence cost, suggesting that it only occurs under a restricted condition.

scholarly journals Food web complexity weakens size-based constraints on the pyramids of life

2020 ◽  
Vol 287 (1934) ◽  
pp. 20201500
Author(s):  
C. B. Woodson ◽  
J. R. Schramski ◽  
S. B. Joye
Keyword(s):  
Energy Transfer ◽  
Food Web ◽  
Food Webs ◽  
Trophic Structure ◽  
Marine Ecosystems ◽  
Top Down ◽  
Bottom Up ◽  
Food Web Complexity ◽  
Structure Inversion ◽  
Energy Pathways

Marine ecosystems are generally expected to have bottom-heavy trophic structure (more plants than animals) due to size-based constraints arising from increased metabolic requirements and inefficient energy transfer. However, size-based (allometric) approaches are often limited to confined trophic-level windows where energy transfer is predicted by size alone and are constrained to a balance between bottom-up and top-down control at steady state. In real food webs, energy flow is more complex and imbalances in top-down and bottom-up processes can also shape trophic structure. We expand the size-based theory to account for complex food webs and show that moderate levels of food web connectance allow for inverted trophic structure more often than predicted, especially in marine ecosystems. Trophic structure inversion occurs due to the incorporation of complex energy pathways and top-down effects on ecosystems. Our results suggest that marine ecosystems should be top-heavy, and observed bottom-heavy trophic structure may be a result of human defaunation of the ocean that has been more extreme than presently recognized.

scholarly journals Food web structure and biocontrol in a four-trophic level system across a landscape complexity gradient

2011 ◽  
Vol 278 (1720) ◽  
pp. 2946-2953 ◽  
Author(s):  
Vesna Gagic ◽  
Teja Tscharntke ◽  
Carsten F. Dormann ◽  
Bernd Gruber ◽  
Anne Wilstermann ◽  
...  
Keyword(s):  
Biological Control ◽  
Food Web ◽  
Food Webs ◽  
Agricultural Landscapes ◽  
Cereal Aphids ◽  
Food Web Structure ◽  
Aphid Parasitoid ◽  
Landscape Complexity ◽  
Food Web Complexity ◽  
Complex Landscapes

Decline in landscape complexity owing to agricultural intensification may affect biodiversity, food web complexity and associated ecological processes such as biological control, but such relationships are poorly understood. Here, we analysed food webs of cereal aphids, their primary parasitoids and hyperparasitoids in 18 agricultural landscapes differing in structural complexity (42–93% arable land). Despite little variation in the richness of each trophic group, we found considerable changes in trophic link properties across the landscape complexity gradient. Unexpectedly, aphid–parasitoid food webs exhibited a lower complexity (lower linkage density, interaction diversity and generality) in structurally complex landscapes, which was related to the dominance of one aphid species in complex landscapes. Nevertheless, primary parasitism, as well as hyperparasitism, was higher in complex landscapes, with primary parasitism reaching levels for potentially successful biological control. In conclusion, landscape complexity appeared to foster higher parasitism rates, but simpler food webs, thereby casting doubt on the general importance of food web complexity for ecosystem functioning.

scholarly journals Soil Food Web Complexity Enhances the Link Between Soil Biodiversity and Ecosystem Multifunctionality in Agricultural Systems

2020 ◽  
Author(s):  
Shuo Jiao ◽  
Yahai Lu ◽  
Gehong Wei
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Ecosystem Functions ◽  
Significant Advance ◽  
Agricultural Systems ◽  
Soil Food Web ◽  
Element Cycling ◽  
Soil Biodiversity ◽  
Multiple Functions ◽  
Food Web Complexity

Abstract Background: Belowground biodiversity supports multiple ecosystem functions and services that humans rely on. However, there is a dearth of studies conducted on a large spatial scale on the topic in intensely managed agricultural ecosystems. Existing studies have overlooked the fact that the functional diversity in other trophic groups within a food web could influence function of an individual in another trophic group. Here, we report significant and positive relationships between soil biodiversity (archaea, bacteria, fungi, protists, and invertebrates) and multiple ecosystem functions (nutrient provisioning, element cycling, and reduced pathogenicity potential) in 228 agricultural fields. Results: The relationships were influenced by (I) the types of organisms with significant relationships in archaea, bacteria, and fungi and not in protists and invertebrates, and (II) the connectedness of dominant phylotypes across soil food webs, which generate different ecological clusters within soil networks to maintain multiple functions. In addition, we highlight the role of soil food web complexity, reflected by ecological networks comprising diverse organisms, which promote the multiple functions and enhance the link between soil biodiversity and ecosystem functions. Conclusions: Overall, our results represent a significant advance in forecasting the impacts of belowground biodiversity within food webs on ecosystem functions in agricultural systems, and suggest that soil biodiversity, particularly soil food web complexity, should not be overlooked, but rather considered a key factor and integrated into policy and management activities aimed at enhancing and maintaining ecosystem productivity, stability, and sustainability under land-use intensification.

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 Loss of consumers constrains phenotypic evolution in the resulting food web

2020 ◽  
Vol 4 (3) ◽  
pp. 266-277
Author(s):  
Matthew A. Barbour ◽  
Christopher J. Greyson‐Gaito ◽  
Arezoo Sotoodeh ◽  
Brendan Locke ◽  
Jordi Bascompte
Keyword(s):  
Food Web ◽  
Phenotypic Evolution

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.

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