Mutualism

10 Key excerpts on "Mutualism"

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  Ecology

  From Ecosystem to Biosphere

  • Christian Leveque(Author)
  • 2003(Publication Date)
  • CRC Press

    (Publisher)

  However, this slightly monolithic approach is no longer widely received, and ecologists have rediscovered the importance of relationship other than competition in the organization of communities. Commensalism, Mutualism, and symbiosis are interactions between species with reciprocal benefits. In a commensal interaction, the host does not benefit (in principle) from the organism to which it offers shelter and cover. Epiphytic Biological Diversity and Ecosystem Functioning 297 plants such as lichens or orchids are examples of commensal organisms. Mutualism is a more evolved form of commensalism since it is obligatory for the organisms involved, with reciprocal benefits, but the species may still live an independent life. Symbiosis involves an obligatory and indissoluble association between two species. In reality, the distinctions are not always easy because they depend largely on the knowledge we have on the biology of the species involved. a) Mutualism Ecologists have challenged the idea that interspecies competition alone explains the great biological diversity presently observed in some communities. They suggest in fact that other types of relationships such as Mutualism and commensalism have been neglected in studies on the organization of communities (Kawanabe and Iwasaki, 1993). In mutualist relationships, the two partners draw a reciprocal benefit from their association. One partner plays a role that may be compared to a service for its associate and, in return, receives a compensation, i.e., it finds an advantage in the association. Such relationships could favour the coexistence of many species having different ecological niches. Mutualism is widespread in nature under extremely diverse forms and comprises relationships between species that live freely and/or species that live in close association throughout their lives.

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  Ecology

  From Individuals to Ecosystems

  • Michael Begon, Colin R. Townsend, John L. Harper(Authors)
  • 2009(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  13.1 Introduction: symbionts, mutualists, commensals and engineers No species lives in isolation, but often the association with another species is especially close: for many organisms, the habitat they occupy is an individual of another species. Parasites live within the body cavities or even the cells of their hosts; nitrogen-fixing bacteria live in nodules on the roots of leguminous plants; and so on. Symbiosis (‘living together’) is the term that has been coined for such close physical associations between species, in which a ‘symbiont’ occupies a habitat provided by a ‘host’. In fact, parasites are usually excluded from the category of sym- bionts, which is reserved instead for interactions where there is at least the suggestion of ‘Mutualism’. A mutualistic relationship is simply one in which organisms of different species interact to their mutual benefit. It usually involves the direct exchange of goods or services (e.g. food, defense or transport) and typically results in the acquisition of novel capabilities by at least one part- ner (Herre et al., 1999). Mutualism, therefore, need not involve close physical association: mutualists need not be symbionts. For example, many plants gain dispersal of their seeds by offering a reward to birds or mammals in the form of edible fleshy fruits, and many plants assure effective pollination by offering a resource of nectar in their flowers to visiting insects. These are mutualistic interactions but they are not symbioses. It would be wrong, however, to see mutualistic interactions simply as conflict-free relationships from which nothing but good things flow for both partners. Rather, current evolutionary thinking views Mutualisms as cases of reciprocal exploitation where, none the less, each partner is a net beneficiary (Herre & West, 1997).

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  A Companion to the Philosophy of Biology

  • Sahotra Sarkar, Anya Plutynski, Sahotra Sarkar, Anya Plutynski(Authors)
  • 2008(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  In animals such as humans with a complex neurology, mutualistic relations, if they occur, tend to be learned rather than instinctual or biochemically mediated. (In humans, therefore, the maintenance of Mutualism is partially a function of culture, broadly kent a. peacock 358 understood.) Highly obligate Mutualisms sometimes lead to symbiogenesis , the creation of a new type of organism. In symbiogenesis, branches of the tree of life occasionally converge, contrary to the classical Darwinian picture where they always keep splitting. L. Margulis (1998) suggests that the formation of symbiotic associations could be a source of evolutionary novelty comparable in importance to mutation, but this view is highly controversial. Margulis has played a leading role in demonstrating the importance of symbiogen-esis in cellular evolution (Margulis, 1998). There is, by now, a large body of evidence supporting serial endosymbiosis, the view that eukaryotic cells are highly obligate mutualistic associations of bacteria. Margulis and E. Odum (1971) highlighted the importance of the “symbiotic transi-tion” in which an opportunistic parasite can move along the symbiotic scale from parasite, through commensal, to obligate mutualist. Such a transition from parasite to mutualist played an essential role in the evolution of eukaryotic cells, in which parasitic bacteria apparently became organelles of the cells they had originally preyed upon. Symbionts will coevolve even if they do not necessarily become mutualists, because a host will evolve to defend itself from a parasite, while the parasite may evolve to cope with the host’s defenses. There is evidence from cell biology that a transition from parasitism to Mutualism will be favored in environments that are closed in a way that leads to resource restric-tion (Margulis and Sagan, 1995), and this is consistent with Kropotkin’s observation (1902/1989) that Mutualism is favored over competition in harsher environments.

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  The Ecological World View

  • Charles Krebs(Author)
  • 2008(Publication Date)
  • CSIRO PUBLISHING

    (Publisher)

  commensalisms .

  Many Mutualisms have been known for hundreds of years. Bees pollinate flowers and gain by obtaining pollen as food, while the plants gain by gene flow (through movement of pollen) and seed fertilization. Nitrogen-fixing bacteria and mycorrhizal fungi inhabit the roots of plants and gain protection and carbohydrates from the plant while supplying nitrogen or other soil nutrients to the plant in exchange. But we should always remember that there are costs to Mutualisms as well as benefits, and we need to determine how the benefits exceed the costs for positive interactions. Ecologists first wish to describe these Mutualisms and then ask how they might affect the distribution and abundance of species in nature (Essay 9.1).

  9.2 MUTUALISTIC INTERACTIONS OCCUR WHEN ANIMALS POLLINATE AND DEFEND PLANTS

  While it is tempting to think of Mutualisms in their simplest form as a two-species interaction—for example, between a particular pollinator and a particular plant species—in natural ecosystems specialized, two-species partnerships are rare. We must remember to think instead of multi-species systems in which, for example, many insects pollinate a particular plant, and a single pollinator may use pollen from several different plant species. For simplicity, most natural history studies concentrate on two-species interactions, from which we can gradually build a more complex picture. Let us consider two examples of Mutualisms.

  ESSAY 9.1 WHY ARE CORALS BLEACHING?

  Coral reef bleaching has increased dramatically in many tropical areas around the globe in the last 20 years. Corals are animals that contain symbiotic algae within their cells, and this symbiotic relationship is one of the most important Mutualisms in the biosphere. The symbiotic algae provide color to the corals and undertake photosynthesis, thus contributing to coral growth—a positive relationship. When corals bleach they lose their symbiotic algae, and therefore their color, and often die. Widespread bleaching can cause the death of whole coral reefs. The primary cause of coral bleaching is thought to be elevated sea surface temperatures. Many reef-building corals live very close to their upper lethal temperatures, and small increases of 0.5 to 1.5°C over a few weeks, or larger increases of 3–4°C over several days, can kill corals (Huppert and Stone 1998

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  Animal Welfare in Animal Agriculture

  Husbandry, Stewardship, and Sustainability in Animal Production

  • Wilson G. Pond, Fuller W. Bazer, Bernard E. Rollin, Wilson G. Pond, Fuller W. Bazer, Bernard E. Rollin(Authors)
  • 2011(Publication Date)
  • CRC Press

    (Publisher)

  There are numerous examples of symbiosis in agriculture. Agriculture in a broad sense involves a symbiotic relationship between humans and plants or animals. Humans plant, fertilize, control weeds and pests, and protect crops. Humans also nurture, feed, and protect livestock. The crops and livestock benefit from human interaction by being more productive and, in turn, they are utilized for food, clothing, shelter, and other human needs. Of more importance are symbioses, particularly interactions of lower order organisms, for example, microorganisms, which can impart health or disease in higher organisms. PARASITISM AND PATHOGENICITY Symbiotic relationships can be further defined or characterized by the type and level of interac-tion (see Figure 9.1). Parasitism describes a system in which one species benefits at the expense of another over time. Pathogenic relationships are often acute interactions in which one species spe-cifically infects and benefits at the expense, and even death, of another. Commensalism describes a system in which one species benefits, but not at the expense of the other. Mutualism describes a system in which both species benefit. Within these types of symbiotic interactions, the level of inter-action can be close contact between the symbionts (ectosymbiosis or exosymbiosis) or it can include one symbiont living inside the other (endosymbiosis). Exploitation of a host can result in symbiosis that is parasitic in nature, and in production agri-culture, these relationships can be costly. In endosymbiotic interactions, immature insects and para-sitic microbes, such as protozoa or bacteria, can reside in a host for periods of time and compete for nutrients. In exosymbiotic instances, parasites, such as pests or insects, can persistently remove nutrients from the host. Regardless of the level of interaction, the loss of nutrients often results in lower yields of crops or reduced performance by the animal. When the parasitic relationship results

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  Unsolved Problems in Ecology

  • Andrew Dobson, David Tilman, Robert D. Holt, Andrew Dobson, David Tilman, Robert D. Holt(Authors)
  • 2020(Publication Date)
  • Princeton University Press

    (Publisher)

  A new ecosystem approach—on an earthwide scale—is the Gaia hypothesis (Lovelock 1988). Whereas a traditional ecosystem study focused on how its species served their ecosystem’s function, Gaia focuses on how the activities of the earth’s organisms collectively make its environment, especially the earth’s temperature, atmospheric composition, and its ocean, river, and soil chemistry more hospitable to life. Automatic, active but unconscious feedback processes maintain this homeostasis. However, “the conditions are only constant in the short term and evolve in synchrony with the changing needs of the biota as it evolves.” (Lovelock 1988, p. 19). Neither an ecosystem nor the ensemble of biogeochemical processes affecting life on earth are true superorganisms because, unlike honeybee colonies, these entities are not organized to reproduce. Nonetheless, natural ecosystems are organized to maintain high productivity and diversity, as evidenced by the circumstance that disturbance outside an ecosystem’s evolutionary experience reduces its productivity and/or diversity (Leigh and Vermeij 2002). Moreover, living things have collectively modified the earth’s surface, making it more suitable for life. Most geochemical cycles have come increasingly under biotic control as life evolved (Vermeij 2013, p. 13; Vermeij 2011, pp. 199–202), so the world is a far better home for life now than 3.7 billion years ago. Ecosystems, individually and collectively, have these features because “by establishing feedbacks between species and enabling factors [factors enhancing access of species to essential resources], effective competitors regulate and enhance resource supply (Vermeij 2013, p. 1).

  Nonetheless, community ecologists rejected the hypothesis of ecosystems as adaptively organized and the Gaia hypothesis that, thanks to their relationships of interdependence, living things collectively make the earth better for life. They did not see how natural selection within populations could favor these developments. Similarly, geologists initially rejected the idea of continental drift even though it fit the facts, because they knew no mechanistic cause for it—but they had to discover new phenomena to explain continental drift, whereas Odum had already proposed the mechanism that shaped ecosystem adaptation and life’s impact on its environment.

  Although how Mutualism helps make organisms better competitors or predators has been studied for decades (Smith and Douglas 1987), as has interdependence among ecosystems (Keast and Morton 1980), Williamson (1972, p. 95) remarked that Mutualism “is a fascinating biological topic, but its importance in populations in general is small.” In their book on symbiosis (a form of Mutualism where one partner lives in the other), Smith and Douglas (1987) assembled evidence that Mutualism—between eukaryotes and their mitochondria, plants and their chloroplasts and mycorrhizae, wood-decomposing termites and the cellulose-consuming protists in their guts, corals and their zooxanthellae—is as vital to the productivity of many, if not most, natural ecosystems as cooperative enterprise is to modern human economies, However, they found that, intracellular organelles excepted, “most biologists consider that the evolutionary importance of symbiosis has been trivial compared to the other mechanisms by which novel and heritable characteristics are produced” (Smith and Douglas 1987, p. 237). Pastor (2008, pp. 169–173) briefly discussed models of Mutualism, but this discussion had no impact on the rest of his book. How could this happen?

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  Cooperation and Conflict

  The Interaction of Opposites in Shaping Social Behavior

  • Walter Wilczynski, Sarah F. Brosnan(Authors)
  • 2021(Publication Date)
  • Cambridge University Press

    (Publisher)

  Therefore, symbionts are very much like cell organelles (mitochondria and chloro- plasts) in the sense that host and symbiont fitness are strongly interdependent: one cannot live without the other, which largely removes any potential for conflict. Interdependency arises in any meta-stable social group. It has been argued to be of particular importance to understand the evolution of the high levels of cooperation observed between unrelated human individuals (Tomasello et al., 2012). The fact that partners in Mutualisms are always unrelated to each other allows us to study causes of interdependency and consequences of cooperation without having to consider potentially confounding effects of altruism based on kin selection. However, inter- dependencies occur more frequently in cases of intraspecific helping, as helping typically takes place within groups of relatively stable composition. In such groups, interaction partners may not only be genetically related to each other (“genetic interdependence”) but their future successes might also be interdependent, which can easily become a game changer (Box 9.2). Both genetic and social interdepend- encies hence favor the evolution and stability of cooperation relative to Mutualisms (Figure 9.1). Similarities between Human Cooperation and Mutualisms Given the three main differences between Mutualisms and cooperation listed above, it emerges that if we want to compare the diversity of human forms of cooperation with other species, some forms are better compared to other examples of cooperation while some forms are better compared to Mutualisms. Most notably, trading in human markets and in Mutualisms feature the exchange of different currencies between 190 Redouan Bshary Box 9.2 Interdependence As a Factor That Stabilizes Cooperation and Mutualism Even very simple game theoretic models make a considerable list of assumptions regarding the social interaction that is analyzed.

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  Interaction and Coevolution

  • John N. Thompson(Author)
  • 2014(Publication Date)
  • University of Chicago Press

    (Publisher)

  CHAPTER 4 ANTAGONISM AND Mutualism

  Mutualisms between species encompass an odd conglomeration of interactions in a world often viewed as “red in tooth and claw.” Although a wide variety of Mutualisms has been described, we still have only a rudimentary understanding of the selection pressures, life history traits, and community attributes that favor the origination and maintenance of these interactions. This lack of a solid understanding of the ecological conditions favoring Mutualisms is reflected in the literature on mathematical models of Mutualisms. Some mathematical and conceptual models conclude that Mutualisms should be expected to be less common in nature than antagonistic interactions, because the models of Mutualism often exhibit high degrees of instability (e.g. May, 1973; Van Valen, 1973; Goh, 1979). Other mathematical models of Mutualism in coevolving species sometimes exhibit stability depending upon the parameters in the models (e.g. Roughgarden, 1975; Levin and Udovic, 1977; Vandermeer and Boucher, 1978; Heithaus et al., 1980; Addicott, 1981). The most reasonable interpretation of the attempts at modeling Mutualisms over the past decade is not that Mutualisms are uncommon—the empirical evidence is to the contrary—but rather that we know little about the ecological bases for Mutualisms relative to antagonistic interactions. I think both modelers and field ecologists would agree with this interpretation. In the book Theoretical Ecology , May (1976, 1981) writes that he would have liked to include a chapter on Mutualism much like the chapters in the book on arthropod predator–prey systems, herbivore–plant systems, and competition and niche theory. He did not because he thought that both the theoretical and empirical bases of Mutualism were still insufficiently known to be summarized as a separate chapter.

  Nevertheless, there are several fronts on which the theory of Mutualism is advancing and some initial syntheses are emerging. This chapter and Chapters 5 and 6

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  Environmental Science & its Components

  • (Author)
  • 2014(Publication Date)
  • Learning Press

    (Publisher)

  This relationship is called commensalism because many other host species receive the benefits of clean air at no cost or harm to the associate tree species supplying the oxygen. The host and associate relationship is called parasitism if one species benefits while the other suffers. Competition among species or among members of the same species is defined as reciprocal antagonism, such as grasses competing for growth space. Parasites: A harvestman arachnid is parasitized by mites. This is parasitism because the spider is being consumed as its juices are slowly sucked out while the mites gain all the benefits traveling on and feeding off of their host. This parasitism may cause the harvestman spider suffering. ________________________ WORLD TECHNOLOGIES ________________________ Popular ecological study systems for Mutualism include, fungus-growing ants employing agricultural symbiosis, bacteria living in the guts of insects and other organisms, the fig wasp and yucca moth pollination complex, lichens with fungi and photosynthetic algae, and corals with photosynthetic algae. Intraspecific behaviours are notable in the social insects, slime moulds, social spiders, human society, and naked mole rats where eusocialism has evolved. Social behaviours include reciprocally beneficial behaviours among kin and nest mates. Social behaviours evolve from kin and group selection. Kin selection explains altruism through genetic relationships, whereby an altruistic behaviour leading to death is rewarded by the survival of genetic copies distributed among surviving relatives. The social insects, including ants, bees and wasps are most famously studied for this type of relationship because the male drones are clones that share the same genetic make-up as every other male in the colony.

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  Arguing for Evolution

  An Encyclopedia for Understanding Science

  • Sehoya H. Cotner, Randy Moore(Authors)
  • 2011(Publication Date)
  • Greenwood

    (Publisher)

  However, populations also accommodate the biotic environment, which includes the other living organisms they typically en- counter. When individuals of two or more species exert selective pressures on each other, the changes that occur are termed coevolution. Organisms that interact are symbionts and the general term for their relationship is symbiosis. Specifically, a symbiosis can be mutualistic, or beneficial to all symbionts, or antagonistic, whereby one or more of the symbionts is nega- tively affected. Antagonism includes competitive, predatory, herbivorous, and parasitic relationships, which often pit interacting lineages in a coevolu- tionary escalation colloquially termed an “arms race.” In addition, com- mensalism describes an interaction in which one symbiont benefits and the other appears unaffected. In amensalism, one symbiont is harmed and the other is unaffected. The importance of these relationships should not be minimized; in fact, most adaptive radiations are attributed to coevolution- ary mechanisms. Ecological Relevance Coevolution is typically inferred when an adaptation is ecologically rele- vant—that is, when an adaptation can be attributed to the presence of other taxa in an organism’s ecosystem. There are many examples of adaptations that are only observed in one species when another species, or group of species, is present. In these cases, the adaptation is ecologically relevant and coevolution is the likely mechanism. Prey Species Possess Ecologically Relevant Adaptations against Predation Adaptations that counter predation include cryptic coloration (i.e., cam- ouflage), mimicry, warning calls and signals, toxic emissions and distaste- ful secretions. Coloration, Mimicry, and Warning Signals Selection makes prey either more visible (e.g., the warning, or apose- matic, coloration of poison arrow frogs) or less visible (e.g., the ability of a cuttlefish to change colors to match its background) to potential preda- tors.

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