Community Interactions

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  Subdisciplines of Ecology (Classification by Level of Complexity or Scope)

  • (Author)
  • 2014(Publication Date)
  • University Publications

    (Publisher)

  ________________________ WORLD TECHNOLOGIES ________________________ Chapter- 10 Community (ecology) Interspecific interactions such as predation are a key aspect of community ecology. In ecology, a community is an assemblage of two or more populations of different species occupying the same geographical a rea. The term community has a variety of uses. In its simplest form it refers to groups of organisms in a specific place and/or time, for example, the fish community of Lake Ontario before industrialization. Community ecologists study the interactions between species in communities on many spatial and temporal scales, including the distribution, structure, abundance, demography, and interactions between coexisting populations. The primary focus of community ecology is on the interactions between populations as determined by specific genotypic ________________________ WORLD TECHNOLOGIES ________________________ and phenotypic characteristics. Community ecology has its origin in European plant sociology. Modern community ecology examines patterns such as variation in species richness, equitability, productivity and food web structure (see community structure; it also examines processes such as predator-prey population dynamics, succession, and community assembly. On a deeper level the meaning and value of the community concept in ecology is up for debate. Communities have traditionally been understood on a fine scale in terms of local processes constructing (or destructing) an assemblage of species, such as the way climate change is likely to affect the make-up of grass communities. Recently this local community focus has bee n criticised. Robert Ricklefs has argued that it's more useful to think of communities on a regional scale, drawing on evolutionary taxonomy and biogeography, where some species or clades evolve and others go extinct. Interspecific interactions Species interact in various ways: competition, predation, parasitism, mutualism, commensalism, etc.

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  Insect Ecology

  An Ecosystem Approach

  • Timothy D. Schowalter(Author)
  • 2016(Publication Date)
  • Academic Press

    (Publisher)

  Section III Community ecology

  Introduction Chapter 8: Species Interactions Chapter 9: Community Structure Chapter 10: Community Dynamics

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  Introduction

  Species co-occurring at a site interact to various degrees, both directly and indirectly, in ways that have intrigued ecologists since the earliest times. These interactions regulate population dynamics, thereby affecting community structure, and also control rates of energy and matter fluxes among organisms, thereby affecting ecosystem function. Some organisms engage in close, direct interactions, as consumers and resources, whereas others interact indirectly in ways that affect activity, such as foraging behavior and reproduction. For example, predation on mimics depends on the presence of their models, and herbivores can be affected by their host’s chemical responses to other herbivores. Direct interactions, that is, competition, predation, and symbioses, have been the focus of research on factors controlling community structure and dynamics, but recent studies have demonstrated that indirect interactions also control community organization. Species interactions are the focus of Chapter 8 .

  A community is composed of the plant, animal, and microbial species occupying a site. Some of these organisms are integral and characteristic components of the community and help define the community type, whereas others occur by chance as a result of dispersal, foraging, or other movement across a landscape or through a watershed. Particular combinations of species distinguish desert, grassland, or forest communities. Different species assemblages are found in turbulent stream versus lake or in eutrophic versus oligotrophic systems. The number of species and their relative abundances define species diversity, an aspect of community structure that is the focus of a number of ecological issues. Chapter 9

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  Ecological Processes Handbook

  • Luca Palmeri, Alberto Barausse, Sven Erik Jorgensen(Authors)
  • 2013(Publication Date)
  • CRC Press

    (Publisher)

  265 © 2008 Taylor & Francis Group, LLC 19 Biological Interactions 19.1 Introduction Organisms in ecosystems are not living isolated but are continuously in inter-action with other organisms either of the same species or with organisms of other species. When we build ecological models, it is crucial to describe these interactions, because the model results are strongly dependent on a close to correct description of at least the most important exchange processes among the state variables. The resources in ecosystems are limited according to the mass and energy conservation principles, which imply that the organ-isms are competing for the resources. Therefore, competition is an important biological interaction. Many population dynamic models have been con-structed to describe this competition (e.g., Lotka–Volterra model) (Jørgensen and Fath, 2011 and Section 19.3). An equally important interaction process is, however, cooperation , because without cooperation no ecosystem will endure. Cooperation is necessary to cycle the resources—for instance the biologi-cally important elements—(see Chapter 12). Without cycling, the limiting elements would be used very fast and further development of the ecosystem would stop, and due to the Second Law of Thermodynamics, the ecosystem would inevitably decompose completely and reach thermodynamic equi-librium. This means that the system is without gradients, free energy, and exergy and the entropy is at maximum. Cycling processes are described in Chapters 13 through 17, and how these processes ensure the cycling is pre-sented in Chapter 12. Chapter 18 considers the processes of particularly toxic substances in ecosystems and their influence on other biological processes. Ecosystems are organized as hierarchical systems and the biological and nonbiological components form networks to ensure that a cycling of the resources can take place.

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  Ocean Ecology

  Marine Life in the Age of Humans

  • J. Emmett Duffy(Author)
  • 2021(Publication Date)
  • Princeton University Press

    (Publisher)

  We cover their consequences for communities and ecosystems in the following two chapters. Interactions among Species: General Considerations The interactions among species within a community can be represented graphically as an interaction web ( figure 7.1 ), where the topology , or structure of the web, consists of arrows showing who affects whom, and the thickness of arrows represents interaction strength , that is, the direct effect that an indi-vidual of one species has on an individual of another species (Wootton and Emmerson 2005). Interac-tion strength is defined mathematically as the per capita effect of one species on the dynamics of an-other species. Interaction strengths can be estimated empirically from experimental removals of consumers or competitors in the field, laboratory feeding assays, or observational approaches integrat-ing gut contents and estimated metabolic requirements. The distributions of interaction strengths within communities are highly uneven, generally with a few very strong interactions, whether positive or negative, and many weak ones. This skewed pattern of interaction strengths has been found in rocky intertidal communities (Paine 1992, Wootton 1994), kelp forests (Sala and Graham 2002), estuarine infauna (Emmerson and Raffaelli 2004), and coral reefs (Bascompte et al. 2005) ( figure 7.2 ). Species in a community interact not just in a pairwise fashion with competitors or predators but with a potentially large number of other species. Meta-analyses comparing the strengths of Species Interactions 7 Figure 7.1. Alternative approaches to characterizing connections among species in communities. Arrow thickness represents (top) presence versus absence of a feeding relationship, (middle) magnitude of energy flow, or (bottom) interaction strength (after Paine 1980).

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  Introduction to Population Ecology

  • Larry L. Rockwood(Author)
  • 2015(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  Part 2 Interspecific interactions among populations At this point we are ready to consider interactions among populations of different species. These interactions may be at the same trophic level (interspecific competition) or between different trophic levels (predator–prey, parasite–host, parasitoid–host, and plant–herbivore interactions). Some of these interactions are considered "symbiotic." A symbiosis is the intimate biotic association of phylogenetically unrelated species, and is thought to develop as a consequence of co-evolution. While symbiosis is sometimes considered exotic or rare in nature, it is actually a rather common phenomenon. For example, the eukaryotic cell appears to be a coevolved symbiotic complex involving organelles such as mitochondria and chloroplasts that were originally free-living organ- isms. Lichens consist of a symbiotic complex of algae living inside fungi, and the roots of higher plants have symbiotic associations with fungi (mycorrhizae). Moreover, the roots of leguminous plants have nodules within which bacteria (Rhizobium and related genera) live. Corals have a symbiotic relationship with algae known as zooxanthellae, and many species of flowering plants have complex relationships with ants. Types of interactions The following are symbolic representations of interactions between two species. In each case the symbol indicates whether the interactions is positive (+), negative (−), or neither for each of the two species involved. −/− = Competition, which is considered to be a reciprocally negative interaction for both of the species involved. +/− = A biological association in which one individual benefits while the other is harmed. Such interactions include predator/prey, herbivore/plant, and parasite/host relationships. +/0 = Commensalism. One partner benefits from the interaction, while the other experiences no particular benefit or harm.

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  Positive Plant Interactions and Community Dynamics

  • Francisco Pugnaire(Author)
  • 2010(Publication Date)
  • CRC Press

    (Publisher)

  Furthermore, this created a new interest in the ecological drivers of biodiversity in natural environments, a topic of research that had interested plant ecologists in the past (Whittaker 1972; Grime 1973; Connell 1978; Huston 1979). In theoretical ecology, biotic interactions are considered to be important driv-ers of community composition and richness, together with chance biogeographi-cal events (e.g., dispersal) and local environmental factors (Lortie et al. 2004; see CONTENTS 4.1 Introduction .................................................................................................... 59 4.2 Biotic Interactions and Biodiversity ............................................................... 60 4.2.1 Competition and Biodiversity ............................................................. 60 4.2.2 Facilitation and Biodiversity ............................................................... 65 4.3 Biodiversity and Ecosystem Function: The Role of Biotic Interactions ......... 68 4.3.1 Niche Complementarity and Selection Effect .................................... 69 4.3.2 Facilitation .......................................................................................... 69 4.4 Reconciling Diversity Experiments and Natural Patterns .............................. 70 4.4.1 The Debate .......................................................................................... 70 4.4.2 Constrained Environments and Facilitation ....................................... 71 4.4.3 Productive Environments and Niche Complementarity ..................... 71 References ................................................................................................................ 75 60 Positive Plant Interactions and Community Dynamics also Figure 6.2 in Chapter 6, this volume). All hypotheses addressing the role of biodiversity for ecosystem functioning have also emphasized the crucial impor-tance of biotic interactions.

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  Plant Invasions

  The Role of Biotic Interactions

  • Anna Traveset, David M. Richardson, Anna Traveset, David M Richardson, David M. Richardson, Anna Traveset, David M Richardson(Authors)
  • 2020(Publication Date)
  • CAB International

    (Publisher)

  The stability of complex natural communities with a multitude of direct interactions can be greatly affected by the type of biotic interactions within it (Tylianakis and Morris, 2017). For instance, mutualistic interactions between species of two guilds in a bipartite network can form a different community topology—stability relationship, distinct from the one which emerged from antagonistic cross-guild interactions (Thébault and Fontaine, 2010). Since most ecological communities are multilayer networks (Pilosof et al., 2017), the proportion of different types of direct interactions becomes an important indicator of network stability (Mougi and Kondoh, 2012), while the ratio of the total number of mutualistic to antagonistic partners to a species can greatly affect its persistence (Melian et al., 2009). Together, composition of interaction types, network size and connectance, and distribution of interaction strength, can all greatly affect community stability, known as the stability criterion (Allesina and Tang, 2012; Landi et al., 2018). When an ecological network is invaded by a number of non-native species, we can formulate this invaded network using a joint dynamical system extending the previous two-species system of equations (Hui and Richardson, 2019b): Note here, N = [ N 1, N 2,..., N m ] T is the vertical vector of population size (abundance) for m number of native (resident) species; A = [ A 1, A 2...., A n ] T is the vertical vector of population size for n number of non-native species. The submatrix M m×m represents the native-to-native interaction block; the submatrix P m×n is the non-native-to-native impact block; the submatrix R n×m represents the native-to-non-native resistance block; the submatrix T n×n represents the non-native- to-non-native (invasional meltdown) block

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  Ecological studies in environmental science: New insights and perspectives

  • Kiran Abasaheb More(Author)
  • 2023(Publication Date)
  • Delve Publishing

    (Publisher)

  On the other hand, amensalism damages one species while aiding another. The interacting species in predation, parasitism, and commensalism all live close to one another. Ecological Studies in Environmental Science: New Insights and Perspectives 136 Key points: • An ecological community consists of all the populations of all the different species that live together in a particular area. • Interactions between different species in a community are called interspecific interactions—inter- means «between.» • Different types of interspecific interactions have different effects on the two participants, which may be positive (+), negative (-), or neutral (0). • The main types of interspecific interactions include competition (-/- ), predation (+/-), mutualism, (+/+), commensalism (+/0), and parasitism (+/-). 6.1.1: Predation Predation occurs when a member of one species consumes the complete or a considerable section of the prey’s body. As a result of this interaction, the predator receives an advantage and the prey suffers an injury (+/-). Herbivory is the act of an animal or insect devouring a plant’s component. Herbivory occurs when one animal or bug preys on another plant species. Predation occurs when members of one species (the predator) prey on members of another species (the prey). Lions and buffaloes are examples of predators and prey. The lion is the ecosystem’s second most dangerous predator. One of its target species is the buffalo, which consumes grass. Buffalo, unlike lions, do not go about killing people. The majority of energy is transported through food chains and food webs along with predator-prey connections. Predator and Prey Population Dynamics : A predator-prey interaction keeps both species in check. Predators may consume more as the number of prey grows. As a result, the number of predators increases in a short period. As the number of predators increases, more prey is taken.

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  Soil Microbiology

  • Robert L. Tate, III(Authors)
  • 2020(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  The impact of an environmental insult on the basic properties of an undisturbed site are commonly of interest at the ecosystem level, but full explanation of the processes occurring therein requires specific targeting of a particular portion of the soil biota. Interactions may be evaluated at the individual organism, population, community, or total ecosystem levels. For most soil inhabitants, definition of the individual is reasonably simply accomplished – the single bacterial, archael, algal, or protozoan cell. This entity is more difficult to define for filamentous organisms, fungi, and some actinomycetes. For most of these organisms, the total mycelial structure developing from a single spore could be considered to be the basic entity of this ecological hierarchy, the individual.

  Above the individual level is the more easily evaluated population. A population is defined as being constituted of all the individuals of the same species or function. More rigorous definitions require a species definition, but in soil microbiology it is not unusual to discuss populations of nitrifiers, denitrifiers, or diazotrophs as well as populations of Bacillus or Pseudomonas spp. The summation of the populations in a particular ecosystem constitutes the community. As indicated above, the ecosystem is the combination of both the living and nonliving components of the environment.

  7.2 Classes of Biological Interactions

  In simple situations, for example an axenic culture growing in a laboratory, the microbial population could be said to be controlled by its nutrient supply, moisture (for colonies growing on solid media), energy source, and a variety of other reasonably defined chemical and physical traits defining the ecosystem. But, even in a defined growth medium, the determinants of cultural development extend beyond the more easily described physical and chemical conditions to the more ill‐understood biological interactions. The microbes are not alone in their ecosystem. Each individual must deal with the physical presence and activity of their progeny. Even if a microbe enters a new habitat as a single spore and no other organisms are present – a highly unlikely situation – the primary product of the pioneer is its progeny. That is, for successful colonization of the site to occur, the growing, respiring microbe must replicate. At the least, the presence of this new cell results in competition for nutrients and space as well as an increase in waste materials accumulated in the vicinity of the developing microcolony. These parent–progeny interactions are simple in that the phenotypic and genotypic differences between the cells are minimal. Except for any mutations that may have resulted during the division cycle, each cell is essentially identical. Thus, each microbial cell may be considered to have equal capability and opportunity in the competition for available resources.

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  Coexistence in Ecology

  A Mechanistic Perspective

  • Mark A. McPeek(Author)
  • 2022(Publication Date)
  • Princeton University Press

    (Publisher)

  Community ecologists can ask a multitude of different questions of various scopes about these interaction networks, and different questions will require the I N T R O D U C T I O N 1 5 researcher to consider the interaction network at different spatial and temporal scales. Most community ecologists are initially interested in the role of particular taxa or assemblages or trophic levels in the community, and so all questions begin with these species as the focus. Initially, only the components of the interaction network that directly impact their demographic rates and abundances will be impor- tant. Thus, for a community ecologist interested in understanding some aspects of the community ecology of Daphnia species found in the pelagic zone of a lake, the components of this interaction network that directly affect Daphnia species’ demo- graphic rates and abundances are most relevant; that is, the algal species on which they feed and the predators that feed on them. Depending on the questions being addressed, it may also be important to understand more distant parts of the interac- tion network that influence the abundances of these species. And so, typically, one will start with some specific component of the web and work out through various connections, because components of the interaction web that do not directly or indi- rectly influence the components of interest are irrelevant to study. The extent of the network of interactions that one wants to or is forced to study is primarily determined by the questions being addressed by the researcher. This is because species composition in one part of a local food web intimately depends on the species that occupy other parts of the food web. In fact, a food web repre- sents much (but not all) of the causal network of species interactions that consti- tutes a biological community. For some taxa and some types of questions, only adjacent portions of the local interaction network are necessary.

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