scholarly journals Biotic Interactions in Experimental Antarctic Soil Microcosms Vary with Abiotic Stress

Soil Systems ◽  
2019 ◽  
Vol 3 (3) ◽  
pp. 57
Author(s):  
E. Ashley Shaw ◽  
Diana H. Wall
Keyword(s):  
High Salinity ◽  
Abiotic Factors ◽  
Biotic Interactions ◽  
Trophic Relationships ◽  
Salinity Treatment ◽  
Ecological Communities ◽  
Dry Valleys ◽  
Top Down ◽  
Terrestrial Vertebrates ◽  
The Many

Biotic interactions structure ecological communities but abiotic factors affect the strength of these relationships. These interactions are difficult to study in soils due to their vast biodiversity and the many environmental factors that affect soil species. The McMurdo Dry Valleys (MDV), Antarctica, are relatively simple soil ecosystems compared to temperate soils, making them an excellent study system for the trophic relationships of soil. Soil microbes and relatively few species of nematodes, rotifers, tardigrades, springtails, and mites are patchily distributed across the cold, dry landscape, which lacks vascular plants and terrestrial vertebrates. However, glacier and permafrost melt are expected to cause shifts in soil moisture and solutes across this ecosystem. To test how increased moisture and salinity affect soil invertebrates and their biotic interactions, we established a laboratory microcosm experiment (4 community × 2 moisture × 2 salinity treatments). Community treatments were: (1) Bacteria only (control), (2) Scottnema (S. lindsayae + bacteria), (3) Eudorylaimus (E. antarcticus + bacteria), and (4) Mixed (S. lindsayae + E. antarcticus + bacteria). Salinity and moisture treatments were control and high. High moisture reduced S. lindsayae adults, while high salinity reduced the total S. lindsayae population. We found that S. lindsayae exerted top-down control over soil bacteria populations, but this effect was dependent on salinity treatment. In the high salinity treatment, bacteria were released from top-down pressure as S. lindsayae declined. Ours was the first study to empirically demonstrate, although in lab microcosm conditions, top-down control in the MDV soil food web.

scholarly journals Abiotic factors influence patterns of bacterial diversity and community composition in the Dry Valleys of Antarctica

2020 ◽  
Vol 96 (5) ◽  
Author(s):  
Eric M Bottos ◽  
Daniel C Laughlin ◽  
Craig W Herbold ◽  
Charles K Lee ◽  
Ian R McDonald ◽  
...  
Keyword(s):  
Community Composition ◽  
Bacterial Communities ◽  
Structural Equation ◽  
Abiotic Factors ◽  
Biotic Interactions ◽  
Equation Modeling ◽  
Dry Valleys ◽  
Physicochemical Variables ◽  
Soil Conductivity ◽  
Community Dissimilarity

ABSTRACT The Dry Valleys of Antarctica are a unique ecosystem of simple trophic structure, where the abiotic factors that influence soil bacterial communities can be resolved in the absence of extensive biotic interactions. This study evaluated the degree to which aspects of topographic, physicochemical and spatial variation explain patterns of bacterial richness and community composition in 471 soil samples collected across a 220 square kilometer landscape in Southern Victoria Land. Richness was most strongly influenced by physicochemical soil properties, particularly soil conductivity, though significant trends with several topographic and spatial variables were also observed. Structural equation modeling (SEM) supported a final model in which variation in community composition was best explained by physicochemical variables, particularly soil water content, and where the effects of topographic variation were largely mediated through their influence on physicochemical variables. Community dissimilarity increased with distance between samples, and though most of this variation was explained by topographic and physicochemical variation, a small but significant relationship remained after controlling for this environmental variation. As the largest survey of terrestrial bacterial communities of Antarctica completed to date, this work provides fundamental knowledge of the Dry Valleys ecosystem, and has implications globally for understanding environmental factors that influence bacterial distributions.

Community Ecology of Stream Fishes: Concepts, Approaches, and Techniques

2010 ◽  
Keyword(s):  
Community Ecology ◽  
Fish Assemblages ◽  
Abiotic Factors ◽  
Biotic Interactions ◽  
Theoretical Models ◽  
Field Studies ◽  
Structure And Function ◽  
Activity Levels ◽  
Ecological Communities ◽  
And Function

<em>Abstract</em>.—Ecological communities are structured by a combination of stochastic and deterministic processes, the latter including both abiotic factors and biotic interactions such as predation. Many studies, mostly in relatively stable ecosystems such as lakes, have demonstrated top-down effects on community structure and function. Communities or species in dynamic nonequilibrium ecosystems such as streams may also respond strongly to predation pressure. In this chapter, we review experimental research on effects of predation on fish assemblages in lotic systems, focusing on developments in the decades since Matthews and Heins (1987). Direct experimental evidence indicates that predators strongly affect lotic fish assemblages via direct and indirect pathways of lethal and nonlethal interactions. Across studies, predators consistently reduced prey density, caused changes in prey habitat use, and decreased prey activity levels. Predators may also affect aspects of prey life history and reproduction in streams, and the presence of multiple predator species may result in prey risk enhancement. Our review identified five areas needing additional research that may lead to further advances in stream fish community ecology: (1) linking predation experiments with theoretical models of fish assemblage structure and function, (2) quantifying functional traits of predators and prey, (3) manipulating whole assemblages and testing multispecies interactions, (4) understanding the role of predation in human-modified ecosystems, and (5) application of analytical approaches that facilitate integration among these areas of research as well as with observational field studies.

Desert Biome

Ecology ◽  
2012 ◽  
Author(s):  
David Ward
Keyword(s):  
Biotic Interactions ◽  
Annual Precipitation ◽  
Dry Valleys ◽  
Desert Ecosystems ◽  
Mountain Ranges ◽  
Common Definition ◽  
Global Atmospheric Circulation ◽  
The Many ◽  
The Tropics ◽  
Average Annual Precipitation

Deserts are defined by their arid conditions. However, deserts are not necessarily dry. It is the high evaporation relative to the precipitation that makes a desert such a harsh environment. Such evaporation occurs because deserts are often, but not always, hot, and because precipitation is low. A result of this aridity is that most of the area occupied by deserts is barren and monotonous. However, biologists perceive deserts to be laboratories of nature, where natural selection is exposed at its most extreme. Scientists have long considered the many unique adaptations of plants and animals for surviving the harsh desert environment. More recently, researchers have focused on the biotic interactions among organisms. Thus, the harsh abiotic environment defines the desert and imposes the strong selection pressures on organisms that live there. However, it is the relative simplicity of desert ecosystems that makes them frequently more tractable for study than more complex environments such as forests. According to Gideon Louw and Mary Seely’s Ecology of Desert Organisms (Louw and Seely 1982, cited under General Overviews) and John Sowell’s Desert Ecology (Sowell 2001, cited under Specific Deserts), most deserts have an average annual precipitation of less than 400 mm. A common definition distinguishes between true deserts, which receive less than 250 mm of average annual precipitation, and semideserts or steppes, which receive between 250 mm and 400 to 500 mm. Four factors influence the lack of rainfall in deserts: (1) the global atmospheric circulation maintains twin belts of dry, high-pressure air over the edges of the tropics, called Hadley cells; (2) marine circulation patterns contribute to aridity when cold coastal waters on the west coasts of North and South America, Africa, and Australia chill the air, reducing its moisture-carrying capacity; (3) rain shadows are created by mountain ranges; and (4) if the distances to the interior of a continent are too great (such as in the Gobi and Taklamakan deserts of China), then water is limited. Many of these four factors act in tandem. An additional type of desert is the polar desert, which occurs in the McMurdo dry valleys of Antarctica. This desert has extremely low humidity and no snow cover. Katabatic winds, which occur when cold and dense air is pulled down by gravity, heat as they descend and evaporate all moisture (see Doran, et al. 2002, cited under Defining the Desert Biome). These winds can reach speeds in excess of 300 km per hour. Here too, rain shadows are created by mountain ranges that are sufficiently high that the seaward-flowing ice is blocked from reaching the sea, thereby reducing humidity.

scholarly journals Warming decreases host survival with multiple parasitoids, but parasitoid performance also decreases

2021 ◽  
Author(s):  
Mélanie Thierry ◽  
Nicholas A. Pardikes ◽  
Benjamin Rosenbaum ◽  
Miguel G. Ximénez-Embún ◽  
Jan Hrček
Keyword(s):  
Ecosystem Functioning ◽  
Species Interactions ◽  
Community Dynamics ◽  
Abiotic Factors ◽  
Interactive Effects ◽  
Global Changes ◽  
Ecological Communities ◽  
Top Down ◽  
Multiple Predators ◽  
Abiotic And Biotic Factors

AbstractCurrent global changes are reshaping ecological communities and modifying environmental conditions. We need to recognize the combined impact of these biotic and abiotic factors on species interactions, community dynamics and ecosystem functioning. Specifically, the strength of predator-prey interactions often depends on the presence of other natural enemies: it weakens with competition and interference, or strengthens with facilitation. Such effects of multiple predators on prey are likely to be affected by changes in the abiotic environment, altering top-down control, a key structuring force in both natural and agricultural ecosystems. Here, we investigated how warming alters the effects of multiple predators on prey suppression using a dynamic model coupled with empirical laboratory experiments with Drosophila-parasitoid communities. While the effects of multiple parasitoids on host suppression were the average of the effects of individual parasitoid at ambient temperature, host suppression with multiple parasitoids was higher than expected under warming. Multiple parasitoid species had equivalent effect to multiple individuals of a same species. While multiple parasitoids enhanced top-down control under warming, parasitoid performance generally declined when another parasitoid was present due to competitive interactions, which could reduce top-down control in the long-term. Our study highlights the importance of accounting for interactive effects between abiotic and biotic factors to better predict community dynamics in a rapidly changing world, and better preserve ecosystem functioning and services such as biological control.

Biotics: Competition, Herbivory, Predation, Parasitism and Symbiosis

2017 ◽  
Author(s):  
Christer Brönmark ◽  
Lars-Anders Hansson
Keyword(s):  
Population Dynamics ◽  
Ecosystem Function ◽  
Theoretical Basis ◽  
Abiotic Factors ◽  
Biological Interactions ◽  
Natural Systems ◽  
The Many

If biological interactions, such as competition and predation, have any effect on population dynamics, or if abiotic factors alone determine which organisms, how many of them do we see in a specific ecosystem, was for long a controversial question. This chapter aims at providing the basis for the understanding of biological interactions, as well as showing ample examples of how important those interactions are in shaping both population dynamics and ecosystem function of natural systems. In addition to the many examples, the reader is introduced to the history and the theoretical basis for biological interactions.

scholarly journals Identifying appropriate sampling and modelling approaches for analysing distributional patterns of Antarctic terrestrial arthropods along the Victoria Land latitudinal gradient

2010 ◽  
Vol 22 (6) ◽  
pp. 742-748 ◽  
Author(s):  
Tancredi Caruso ◽  
Ian D. Hogg ◽  
Roberto Bargagli
Keyword(s):  
Abiotic Factors ◽  
Relevant Literature ◽  
Biotic Interactions ◽  
Terrestrial Ecosystems ◽  
Climatic Conditions ◽  
Trophic Levels ◽  
Terrestrial Arthropods ◽  
Victoria Land ◽  
Dispersal Capability ◽  
Modelling Techniques

AbstractBiotic communities in Antarctic terrestrial ecosystems are relatively simple and often lack higher trophic levels (e.g. predators); thus, it is often assumed that species’ distributions are mainly affected by abiotic factors such as climatic conditions, which change with increasing latitude, altitude and/or distance from the coast. However, it is becoming increasingly apparent that factors other than geographical gradients affect the distribution of organisms with low dispersal capability such as the terrestrial arthropods. In Victoria Land (East Antarctica) the distribution of springtail (Collembola) and mite (Acari) species vary at scales that range from a few square centimetres to regional and continental. Different species show different scales of variation that relate to factors such as local geological and glaciological history, and biotic interactions, but only weakly with latitudinal/altitudinal gradients. Here, we review the relevant literature and outline more appropriate sampling designs as well as suitable modelling techniques (e.g. linear mixed models and eigenvector mapping), that will more adequately address and identify the range of factors responsible for the distribution of terrestrial arthropods in Antarctica.

Environmental–biomechanical reciprocity and the evolution of plant material properties

2021 ◽  
Author(s):  
Karl J Niklas ◽  
Frank W Telewski
Keyword(s):  
Physical Environment ◽  
Structural Changes ◽  
Abiotic Factors ◽  
Biotic Interactions ◽  
Cellular Solids ◽  
Form And Function ◽  
Evolutionary Innovation ◽  
Plant Form ◽  
And Function ◽  
Abiotic Environmental Factors

Abstract Abiotic–biotic interactions have shaped organic evolution since life first began. Abiotic factors influence growth, survival, and reproductive success, whereas biotic responses to abiotic factors have changed the physical environment (and indeed created new environments). This reciprocity is well illustrated by land plants who begin and end their existence in the same location while growing in size over the course of years or even millennia, during which environment factors change over many orders of magnitude. A biomechanical, ecological, and evolutionary perspective reveals that plants are (i) composed of materials (cells and tissues) that function as cellular solids (i.e. materials composed of one or more solid and fluid phases); (ii) that have evolved greater rigidity (as a consequence of chemical and structural changes in their solid phases); (iii) allowing for increases in body size and (iv) permitting acclimation to more physiologically and ecologically diverse and challenging habitats; which (v) have profoundly altered biotic as well as abiotic environmental factors (e.g. the creation of soils, carbon sequestration, and water cycles). A critical component of this evolutionary innovation is the extent to which mechanical perturbations have shaped plant form and function and how form and function have shaped ecological dynamics over the course of evolution.

scholarly journals Effects of Abiotic Factors on HIPV-Mediated Interactions between Plants and Parasitoids

2015 ◽  
Vol 2015 ◽  
pp. 1-18 ◽  
Author(s):  
Christine Becker ◽  
Nicolas Desneux ◽  
Lucie Monticelli ◽  
Xavier Fernandez ◽  
Thomas Michel ◽  
...  
Keyword(s):  
Plant Volatiles ◽  
Global Climate ◽  
Abiotic Factors ◽  
Biotic Interactions ◽  
Green Leaf Volatiles ◽  
Limited Attention ◽  
Emission Rates ◽  
Leaf Volatiles ◽  
Parasitic Hymenoptera ◽  
Growing Conditions

In contrast to constitutively emitted plant volatiles (PV), herbivore-induced plant volatiles (HIPV) are specifically emitted by plants when afflicted with herbivores. HIPV can be perceived by parasitoids and predators which parasitize or prey on the respective herbivores, including parasitic hymenoptera. HIPV act as signals and facilitate host/prey detection. They comprise a blend of compounds: main constituents are terpenoids and “green leaf volatiles.” Constitutive emission of PV is well known to be influenced by abiotic factors like temperature, light intensity, water, and nutrient availability. HIPV share biosynthetic pathways with constitutively emitted PV and might therefore likewise be affected by abiotic conditions. However, the effects of abiotic factors on HIPV-mediated biotic interactions have received only limited attention to date. HIPV being influenced by the plant’s growing conditions could have major implications for pest management. Quantitative and qualitative changes in HIPV blends may improve or impair biocontrol. Enhanced emission of HIPV may attract a larger number of natural enemies. Reduced emission rates or altered compositions, however, may render blends imperceptible to parasitoides and predators. Predicting the outcome of these changes is highly important for food production and for ecosystems affected by global climate change.

Revisiting the synopticon: Reconsidering Mathiesen’s ‘The Viewer Society’ in the age of Web 2.0

2011 ◽  
Vol 15 (3) ◽  
pp. 283-299 ◽  
Author(s):  
Aaron Doyle
Keyword(s):  
Mass Media ◽  
Web 2.0 ◽  
Reciprocal System ◽  
The Internet ◽  
Media Production ◽  
Top Down ◽  
The Media ◽  
The Mass Media ◽  
The Many

Thomas Mathiesen’s ‘The Viewer Society’ has been widely influential. Mathiesen posited, alongside the panopticon, a reciprocal system of control, the synopticon, in which ‘the many’ watch ‘the few’. I point to the value of Mathiesen’s arguments but also suggest a reconsideration. I consider where recent challenges to theorizing surveillance as panoptic leave the synopticon. The synopticon is tied to a top—down, instrumental way of theorizing the media. It neglects resistance, alternative currents in media production and reception, the role of culture and the increasing centrality of the internet. Mathiesen’s piece is most useful in a narrower way, in highlighting how surveillance and the mass media interact, rather than in thinking about the role of the media in control more generally.

The role of biotic interactions in invasion ecology: theories and hypotheses.

2020 ◽  
pp. 26-44
Author(s):  
Cang Hui ◽  
◽  
Pietro Landi ◽  
Guillaume Latombe ◽  
◽  
...  
Keyword(s):  
Native Species ◽  
Evolutionary Dynamics ◽  
Biotic Interactions ◽  
Evolutionary Games ◽  
Invasion Ecology ◽  
Ecological Communities ◽  
Dynamic Interactions ◽  
Ecological Fitting ◽  
And Function

Changes in biotic interactions in the native and invaded range can enable a non-native species to establish and spread in novel environments. Invasive non-native species can in turn generate impacts in recipient systems partly through the changes they impose on biotic interactions; these interactions can lead to altered ecosystem processes in the recipient systems. This chapter reviews models, theories and hypotheses on how invasion performance and impact of introduced species in recipient ecosystems can be conjectured according to biotic interactions between native and non-native species. It starts by exploring the nature of biotic interactions as ensembles of ecological and evolutionary games between individuals of both the same and different groups. This allows us to categorize biotic interactions as direct and indirect (i.e. those involving more than two species) that emerge from both coevolution and ecological fitting during community assembly and invasion. We then introduce conceptual models that can reveal the ecological and evolutionary dynamics between interacting non-native and resident species in ecological networks and communities. Moving from such theoretical grounding, we review 20 hypotheses that have been proposed in invasion ecology to explain the invasion performance of a single non-native species, and seven hypotheses relating to the creation and function of assemblages of non-native species within recipient ecosystems. We argue that, although biotic interactions are ubiquitous and quintessential to the assessment of invasion performance, they are nonetheless difficult to detect and measure due to strength dependency on sampling scales and population densities, as well as the non-equilibrium transient dynamics of ecological communities and networks. We therefore call for coordinated efforts in invasion science and beyond, to devise and review approaches that can rapidly map out the entire web of dynamic interactions in a recipient ecosystem.

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