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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 437 (2005), S. 880-883 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Predation can be intense, creating strong direct and indirect effects throughout food webs. In addition, ecologists increasingly recognize that fluxes of organisms across ecosystem boundaries can have major consequences for community dynamics. Species with complex life histories often shift ...
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  • 2
    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 ...
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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Blackwell Science Inc
    Restoration ecology 13 (2005), S. 0 
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Ozark glades are gaps in forested areas that are dominated by grasses and forbs growing in rocky, nutrient-poor soil. Historically, these open, patchy habitats were maintained by natural and anthropogenic fire cycles that prohibited tree encroachment. However, because of decades of fire suppression, glades have become overgrown by fire-intolerant species such as Eastern red cedar (Juniperus virginiana). Current restoration practices include cutting down invasive cedars and burning brush piles, which represent habitat for Northern fence lizards (Sceloporus undulatus). Because Sceloporus actively consumes herbivores, we hypothesized that the presence of these lizards in and around brush piles might result in a trophic cascade, whereby damage on native plants is reduced. Field surveys across six Missouri glades indicated that lizard activity was minimal beyond 1 m from habitat structures. This activity pattern reduced grasshopper abundance by 75% and plant damage by over 66% on Echinacea paradoxa and Rudbeckia missouriensis near structures with lizards. A field transplant experiment demonstrated similar reductions in grasshopper abundance and damage on two other glade endemic species, Aster oblongifolius and Schizachyrium scoparium. These results demonstrate that future glade restoration efforts might benefit from considering top-down effects of predators in facilitating native plant establishment.
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  • 5
    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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  • 6
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    WILEY-BLACKWELL PUBLISHING
    In:  EPIC3Conservation Biology, WILEY-BLACKWELL PUBLISHING, ISSN: 0888-8892
    Publication Date: 2020-11-26
    Description: Estimates of biodiversity change are essential for the management and conservation of ecosystems. Accurate estimates rely on selecting representative sites, but monitoring often focuses on sites of special interest. How such site‐selection biases influence estimates of biodiversity change is largely unknown. Site‐selection bias potentially occurs across four major sources of biodiversity data, decreasing in likelihood from citizen science, museums, national park monitoring, and academic research. We defined site‐selection bias as a preference for sites that are either densely populated (i.e., abundance bias) or species rich (i.e., richness bias). We simulated biodiversity change in a virtual landscape and tracked the observed biodiversity at a sampled site. The site was selected either randomly or with a site‐selection bias. We used a simple spatially resolved, individual‐based model to predict the movement or dispersal of individuals in and out of the chosen sampling site. Site‐selection bias exaggerated estimates of biodiversity loss in sites selected with a bias by on average 300–400% compared with randomly selected sites. Based on our simulations, site‐selection bias resulted in positive trends being estimated as negative trends: richness increase was estimated as 0.1 in randomly selected sites, whereas sites selected with a bias showed a richness change of −0.1 to −0.2 on average. Thus, site‐selection bias may falsely indicate decreases in biodiversity. We varied sampling design and characteristics of the species and found that site‐selection biases were strongest in short time series, for small grains, organisms with low dispersal ability, large regional species pools, and strong spatial aggregation. Based on these findings, to minimize site‐selection bias, we recommend use of systematic site‐selection schemes; maximizing sampling area; calculating biodiversity measures cumulatively across plots; and use of biodiversity measures that are less sensitive to rare species, such as the effective number of species. Awareness of the potential impact of site‐selection bias is needed for biodiversity monitoring, the design of new studies on biodiversity change, and the interpretation of existing data.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 7
    Publication Date: 2017-11-08
    Description: Global concern about human impact on biological diversity has triggered an intense research agenda on drivers and consequences of biodiversity change in parallel with international policy seeking to conserve biodiversity and associated ecosystem functions. Quantifying the trends in biodiversity is far from trivial, however, as recently documented by meta-analyses, which report little if any net change in local species richness through time. Here, we summarise several limitations of species richness as a metric of biodiversity change and show that the expectation of directional species richness trends under changing conditions is invalid. Instead, we illustrate how a set of species turnover indices provide more information content regarding temporal trends in biodiversity, as they reflect how dominance and identity shift in communities over time. We apply these metrics to three monitoring datasets representing different ecosystem types. In all datasets, nearly complete species turnover occurred, but this was disconnected from any species richness trends. Instead, turnover was strongly influenced by changes in species presence (identities) and dominance (abundances). We further show that these metrics can detect phases of strong compositional shifts in monitoring data and thus identify a different aspect of biodiversity change decoupled from species richness. Synthesis and applications: Temporal trends in species richness are insufficient to capture key changes in biodiversity in changing environments. In fact, reductions in environmental quality can lead to transient increases in species richness if immigration or extinction has different temporal dynamics. Thus, biodiversity monitoring programmes need to go beyond analyses of trends in richness in favour of more meaningful assessments of biodiversity change.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 8
    Publication Date: 2021-06-27
    Description: Jähnig et al. make some useful points regarding the conclusions that can be drawn from our meta‐analysis; however, some issues require clarification. First, we never suggested that there was a globally increasing trend of freshwater insect abundances, but only spoke of an average increasing trend in the available data. We also did not suggest that freshwater quality has improved globally, but rather that documented improvements in water quality can explain at least some of the trends we observed. Second, as we acknowledged, our data are not a representative set of freshwater ecosystems around the world, but they are what is currently accessible. Third, there is indeed no doubt that changes in abundance or biomass need not correlate with changes in other aspects of biodiversity, such as species richness or functional composition. Our analysis was specifically focused on trends in community abundance/biomass because it has been the subject of recent study and speculation, and is a widely available metric in long‐term studies. To better understand the recent changes in freshwater insect assemblages, we encourage freshwater ecologists to further open their troves of data from countless long‐term monitoring schemes so that larger and more comprehensive syntheses can be undertaken. This article is categorized under: Water and Life 〉 Conservation, Management, and Awareness
    Description: Biodiversity synthesis is always limited by the available data, but still moves our understanding beyond case studies. Image by Hans Braxmeier from Pixabay.com. image
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: Russian Foundation for Basic Research http://dx.doi.org/10.13039/501100002261
    Keywords: 560 ; arthropods ; biomass ; long‐term ; monitoring ; water quality
    Type: article
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  • 9
    Publication Date: 2023-09-22
    Description: 〈jats:title〉Abstract〈/jats:title〉〈jats:p〉Ecological stability refers to a family of concepts used to describe how systems of interacting species vary through time and respond to disturbances. Because observed ecological stability depends on sampling scales and environmental context, it is notoriously difficult to compare measurements across sites and systems. Here, we apply stochastic dynamical systems theory to derive general statistical scaling relationships across time, space, and ecological level of organisation for three fundamental stability aspects: resilience, resistance, and invariance. These relationships can be calibrated using random or representative samples measured at individual scales, and projected to predict average stability at other scales across a wide range of contexts. Moreover deviations between observed vs. extrapolated scaling relationships can reveal information about unobserved heterogeneity across time, space, or species. We anticipate that these methods will be useful for cross‐study synthesis of stability data, extrapolating measurements to unobserved scales, and identifying underlying causes and consequences of heterogeneity.〈/jats:p〉
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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  • 10
    Publication Date: 2019-07-29
    Description: Biodiversity patterns emerge as a consequence of evolutionary and ecological processes. Their relative importance is frequently tested on model ecosystems such as oceanic islands that vary in both. However, the coarse-scale data typically used in biogeographic studies have limited inferential power to separate the effects of historical biogeographic factors (e.g., island age) from the effects of ecological ones (e.g., island area and habitat heterogeneity). Here, we describe local-scale biodiversity patterns of woody plants using a database of more than 500 forest plots from across the Hawaiian archipelago, where these volcanic islands differ in age by several million years. We show that, after controlling for factors such as island area and heterogeneity, the oldest islands (Kaua’i and O’ahu) have greater native species diversity per unit area than younger islands (Maui and Hawai’i), indicating an important role for macroevolutionary processes in driving not just whole-island differences in species diversity, but also local community assembly. Further, we find that older islands have a greater number of rare species that are more spatially clumped (i.e., higher within-island β-diversity) than younger islands. When we included alien species in our analyses, we found that the signal of macroevolutionary processes via island age was diluted. Our approach allows a more explicit test of the question of how macroevolutionary factors shape not just regional-scale biodiversity, but also local-scale community assembly patterns and processes in a model archipelago ecosystem, and it can be applied to disentangle biodiversity drivers in other systems.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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