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  • 1
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Ecology, Evolution, and Systematics 28 (1997), S. 467-494 
    ISSN: 0066-4162
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Trophic structure, the partitioning of biomass among trophic levels, is a major characteristic of ecosystems. Most studies of the forces that shape trophic structure emphasize either "bottom-up" or "top-down" regulation of populations and communities. Recent work has shown that these two forces are not mutually exclusive alternatives, but efforts to model their interaction still often yield unrealistic predictions. We focus on the problems involved with modeling situations in which community composition, including both the number of trophic levels and the species composition within a trophic level, can change. We review the development of these ideas, emphasizing in particular how compositional change can alter theoretical expectations about the regulation of trophic structure. A comparison of studies on the effects of predators and resource productivity in limnetic ecosystems reveals an intriguing disparity between the results of manipulative experiments and those of correlational studies. We suggest that this contrast is a result of the difference in the temporal scales operating in the two types of studies. Ecosystem-level variables may appear to approach an equilibrium in short-term press experiments; however, processes such as invasion and extinction of species will not have time to play out in most such experiments. We found that the responses of ecosystems to short-term experimental treatments involve less change in species composition than is found in natural communities that have diverged in response to local conditions over longer periods. We argue that the results of short-term experiments support the predictions of models in which the species pool does not change, whereas correlational studies among systems support theories that incorporate compositional change.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 416 (2002), S. 837-841 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Resolving current concerns about the role of biodiversity on ecosystems calls for understanding the separate roles of changes in species numbers and of composition. Recent work shows that primary productivity often, but not always, saturates with species richness within single trophic ...
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 416 (2002), S. 427-430 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The diversity of life is heterogeneously distributed across the Earth. A primary cause for this pattern is the heterogeneity in the amount of energy, or primary productivity (the rate of carbon fixed through photosynthesis), available to the biota in a given location. But the ...
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 360 (1992), S. 341-343 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We manipulated food-web structure and nutrients in mesocosms that mimic natural ponds18'19 to test for a food web-by-nutrient interaction on aquatic organisms. We created four food-webs by manipulating the occurrences of two important herbivores, Rana utricularia tadpoles20 and Daphnia laevis15 and ...
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 109 (1997), S. 561-570 
    ISSN: 1432-1939
    Keywords: Key words Habitat selection  ;  Clonal specialization  ; Daphnia behavior and body size  ;  Population differentiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Many species of planktonic cladocerans display substantial variation in habitat use (mean depth and diel vertical migration), both among and within populations. We examined whether clonal segregation and specialization contributes to such behavioral variation within several lake populations of the cladoceran, Daphnia pulicaria. Electrophoretic and quantitative genetic analysis of clonal lines isolated from different depths at night revealed that clonal habitat specialization was common. Clones that utilized shallow water at night were genetically smaller at maturity and lower fecundity under standard laboratory conditions than the deep-water clones. The magnitude of this clonal habitat specialization varied among lakes: populations displaying broad use of depth habitats contained greater genetic variance than populations with more constrained habitat use. These results are consistent with known differences in selective factors in different depth habitats and suggest that substantial clonal specialization can occur within single populations. Since previous work has discovered a heritable basis to habitat selection in several Daphnia species, including D. pulicaria in our study lakes, it is likely that clonal/depth specialization is an important factor affecting the trophic ecology of Daphnia.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 110 (1997), S. 132-142 
    ISSN: 1432-1939
    Keywords: Key words Resource competition  ;  Nutrient availability  ;  Light competition  ;  Herbivory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Recent theory on resource competition, predicated on the importance of hypothesized trade-offs between minimum requirements for nutrient resources, predicts that there should be negative correlations between the supply rate of major limiting nutrients and the availability of at least some secondary nutrients and/or among the availabilities of different limiting nutrients. However, an analysis of four data sets from large-scale surveys of lakes shows mostly positive correlations among the availabilities and supplies of nutrients. In contrast, a fifth data set, obtained in an area of high acidification, does show several important negative correlations that are consistent with the nutrient competition models. Further analyses suggest two possible explanations for the preponderance of positive correlation. Negative correlations between nutrients and light indicate that an important trade-off among species regulating phytoplankton may involve low light requirements versus low nutrient requirements. The existence of negative correlations in nutrient availabilities in acidic lakes (where herbivory appears less important than in buffered lakes) also suggests that another important trade-off may involve an ability to minimize loss rates (especially due to grazing) versus an overall ability to exploit nutrient resources.
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  • 7
    ISSN: 1573-8477
    Keywords: coexistence ; food webs ; herbivory ; plant resistance ; plant tolerance ; priority effects ; trade-offs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract While evolutionary ecologists emphasize different ways in which plants can evolutionarily respond to herbivory, such as resistance or tolerance, community ecology has lagged in its understanding of how these different plant traits can influence interactions, abundance, composition, and diversity within more complex food webs. In this paper, we present a series of models comparing community level outcomes when plants either resist or tolerate herbivory. We show that resistance and tolerance can lead to very different outcomes. A particularly important result is that resistant species should often coexist locally with other, less resistant competitors, whereas tolerant species should not be able to coexist locally with less tolerant competitors, although priority effects allow them to coexist regionally. We also use these models to suggest some insights into the evolution of these traits within more complex communities. We emphasize how understanding the differential effects of plant tolerance and resistance in food webs provides greater appreciation of a variety of empirical patterns that heretofore have appeared enigmatic.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Evolutionary ecology 12 (1997), S. 95-110 
    ISSN: 1573-8477
    Keywords: apparent competition ; character displacement ; co-existence ; keystone predator ; limiting similarity ; regional biotas ; resource competition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The notion of ‘community-wide character displacement’ hypothesizes that locally co-existing sets of competing species should be less similar than expected when compared to random expectations from a broader regional species pool. Here I use a mechanistic approach to the niche concept to show how this expectation is dependent on the types of traits involved. I investigate how two different niche components, those that relate to species' requirements (or responses to environmental factors) versus those that relate to species' impacts (or effects on environmental factors), affect predictions about the similarity of locally co-existing species. In contrast with more conventional approaches that focus on species impacts, I focus on species responses to conclude that locally co-existing species should be more similar in such traits than expected on the basis of random assortment from a larger equilibrium regional biota. In addition, I explore the evolutionary implications of exceptions that might favour the co-existence of species with dissimilar traits (especially those that determine species' impacts on the environment) and conclude that these implications differ when species compete for shared resources, interact via shared predators, or interact via both mechanisms. The analysis developed in this paper shows that the co-existence of species that are more similar than expected by chance is not incompatible with the notion of strongly interacting species in saturated local communities near equilibrium.
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  • 9
    Publication Date: 2018-01-10
    Description: The research of a generation of ecologists was catalysed by the recognition that the number and identity of species in communities influences the functioning of ecosystems. The relationship between biodiversity and ecosystem functioning (BEF) is most often examined by controlling species richness and randomising community composition. In natural systems, biodiversity changes are often part of a bigger community assembly dynamic. Therefore, focusing on community assembly and the functioning of ecosystems (CAFE), by integrating both species richness and composition through species gains, losses and changes in abundance, will better reveal how community changes affect ecosystem function. We synthesise the BEF and CAFE perspectives using an ecological application of the Price equation, which partitions the contributions of richness and composition to function. Using empirical examples, we show how the CAFE approach reveals important contributions of composition to function. These examples show how changes in species richness and composition driven by environmental perturbations can work in concert or antagonistically to influence ecosystem function. Considering how communities change in an integrative fashion, rather than focusing on one axis of community structure at a time, will improve our ability to anticipate and predict changes in ecosystem function.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 10
    Publication Date: 2020-07-08
    Description: Historically, many biologists assumed that evolution and ecology acted independently because evolution occurred over distances too great to influence most ecological patterns. Today, evidence indicates that evolution can operate over a range of spatial scales, including fine spatial scales. Thus, evolutionary divergence across space might frequently interact with the mechanisms that also determine spatial ecological patterns. Here, we synthesize insights from 500 eco-evolutionary studies and develop a predictive framework that seeks to understand whether and when evolution amplifies, dampens, or creates ecological patterns. We demonstrate that local adaptation can alter everything from spatial variation in population abundances to ecosystem properties. We uncover 14 mechanisms that can mediate the outcome of evolution on spatial ecological patterns. Sometimes, evolution amplifies environmental variation, especially when selection enhances resource uptake or patch selection. The local evolution of foundation or keystone species can create ecological patterns where none existed originally. However, most often, we find that evolution dampens existing environmental gradients, because local adaptation evens out fitness across environments and thus counteracts the variation in associated ecological patterns. Consequently, evolution generally smooths out the underlying heterogeneity in nature, making the world appear less ragged than it would be in the absence of evolution. We end by highlighting the future research needed to inform a fully integrated and predictive biology that accounts for eco-evolutionary interactions in both space and time.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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