| 1. |
- Brose, Ulrich, et al.
(författare)
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Body sizes of consumers and their resources
- 2005
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Ingår i: Ecology. - : Ecological Society of America. - 0012-9658 .- 1939-9170. ; 86:9, s. 2545-2545
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Tidskriftsartikel (refereegranskat)abstract
- Trophic information—who eats whom—and species’ body sizes are two of the most basic descriptions necessary to understand community structure as well as ecological and evolutionary dynamics. Consumer–resource body size ratios between predators and their prey, and parasitoids and their hosts, have recently gained increasing attention due to their important implications for species’ interaction strengths and dynamical population stability. This data set documents body sizes of consumers and their resources. We gathered body size data for the food webs of Skipwith Pond, a parasitoid community of grass-feeding chalcid wasps in British grasslands; the pelagic community of the Benguela system, a source web based on broom in the United Kingdom; Broadstone Stream, UK; the Grand Caric¸aie marsh at Lake Neuchaˆtel, Switzerland; Tuesday Lake, USA; alpine lakes in the Sierra Nevada of California; Mill Stream, UK; and the eastern Weddell Sea Shelf, Antarctica. Further consumer–resource body size data are included for planktonic predators, predatory nematodes, parasitoids, marine fish predators, freshwater invertebrates, Australian terrestrial consumers, and aphid parasitoids. Containing 16 807 records, this is the largest data set ever compiled for body sizes of consumers and their resources. In addition to body sizes, the data set includes information on consumer and resource taxonomy, the geographic location of the study, the habitat studied, the type of the feeding interaction (e.g., predacious, parasitic) and the metabolic categories of the species (e.g., invertebrate, ectotherm vertebrate). The present data set was gathered with the intent to stimulate research on effects of consumer–resource body size patterns on food-web structure, interaction-strength distributions, population dynamics, and community stability. The use of a common data set may facilitate cross-study comparisons and understanding of the relationships between different scientific approaches and models.
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| 2. |
- Barnes, Andrew D., et al.
(författare)
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Direct and cascading impacts of tropical land-use change on multi-trophic biodiversity
- 2017
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Ingår i: Nature Ecology and Evolution. - : Springer Science and Business Media LLC. - 2397-334X. ; 1:10, s. 1511-1519
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Tidskriftsartikel (refereegranskat)abstract
- The conversion of tropical rainforest to agricultural systems such as oil palm alters biodiversity across a large range of interacting taxa and trophic levels. Yet, it remains unclear how direct and cascading effects of land-use change simultaneously drive ecological shifts. Combining data from a multi-taxon research initiative in Sumatra, Indonesia, we show that direct and cascading land-use effects alter biomass and species richness of taxa across trophic levels ranging from microorganisms to birds. Tropical land use resulted in increases in biomass and species richness via bottom-up cascading effects, but reductions via direct effects. When considering direct and cascading effects together, land use was found to reduce biomass and species richness, with increasing magnitude at higher trophic levels. Our analyses disentangle the multifaceted effects of land-use change on tropical ecosystems, revealing that biotic interactions on broad taxonomic scales influence the ecological outcome of anthropogenic perturbations to natural ecosystems.
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| 3. |
- Binzer, Amrei, et al.
(författare)
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Interactive effects of warming, eutrophication and size structure: impacts on biodiversity and food-web structure
- 2016
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Ingår i: Global Change Biology. - : WILEY-BLACKWELL. - 1354-1013 .- 1365-2486. ; 22:1, s. 220-227
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Tidskriftsartikel (refereegranskat)abstract
- Warming and eutrophication are two of the most important global change stressors for natural ecosystems, but their interaction is poorly understood. We used a dynamic model of complex, size-structured food webs to assess interactive effects on diversity and network structure. We found antagonistic impacts: Warming increases diversity in eutrophic systems and decreases it in oligotrophic systems. These effects interact with the community size structure: Communities of similarly sized species such as parasitoid-host systems are stabilized by warming and destabilized by eutrophication, whereas the diversity of size-structured predator-prey networks decreases strongly with warming, but decreases only weakly with eutrophication. Nonrandom extinction risks for generalists and specialists lead to higher connectance in networks without size structure and lower connectance in size-structured communities. Overall, our results unravel interactive impacts of warming and eutrophication and suggest that size structure may serve as an important proxy for predicting the community sensitivity to these global change stressors.
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| 4. |
- Binzer, Amrei, et al.
(författare)
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The susceptibility of species to extinctions in model communities
- 2011
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Ingår i: Basic and Applied Ecology. - : Elsevier. - 1439-1791 .- 1618-0089. ; 12:7, s. 590-599
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Tidskriftsartikel (refereegranskat)abstract
- Despite the fact that the loss of a species from a community has the potential to cause a dramatic decline in biodiversity, for example through cascades of secondary extinctions, little is known about the factors contributing to the extinction risk of any particular species. Here we expand earlier modeling approaches using a dynamic food-web model that accounts for bottom-up as well as top-down effects. We investigate what factors influence a species’ extinction risk and time to extinction of the non-persistent species. We identified three basic properties that affect a species’ risk of extinction. The highest extinction risk is born by species with (1) low energy input (e.g. high trophic level), (2) susceptibility to the loss of energy pathways (e.g. specialists with few prey species) and (3) dynamic instability (e.g. low Hill exponent and reliance on homogeneous energy channels when feeding on similarly sized prey). Interestingly, and different from field studies, we found that the trophic level and not the body mass of a species influences its extinction risk. On the other hand, body mass is the single most important factor determining the time to extinction of a species, resulting in small species dying first. This suggests that in the field the trophic level might have more influence on the extinction risk than presently recognized.
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| 5. |
- Brose, Ulrich, et al.
(författare)
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Consumer-resource body-size relationships in natural food webs
- 2006
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Ingår i: Ecology. - : Ecological Society of America esa. - 0012-9658 .- 1939-9170. ; 87:10, s. 2411-2417
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Tidskriftsartikel (refereegranskat)abstract
- It has been suggested that differences in body size between consumer and resource species may have important implications for interaction strengths, population dynamics, and eventually food web structure, function, and evolution. Still, the general distribution of consumer-'resource body-size ratios in real ecosystems, and whether they vary systematically among habitats or broad taxonomic groups, is poorly understood. Using a unique global database on consumer and resource body sizes, we show that the mean body-size ratios of aquatic herbivorous and detritivorous consumers are several orders of magnitude larger than those of carnivorous predators. Carnivorous predator-prey body-size ratios vary across different habitats and predator and prey types (invertebrates, ectotherm, and endotherm vertebrates). Predator-prey body-size ratios are on average significantly higher (1) in freshwater habitats than in marine or terrestrial habitats, (2) for vertebrate than for invertebrate predators, and (3) for invertebrate than for ectotherm vertebrate prey. If recent studies that relate body-size ratios to interaction strengths are general, our results suggest that mean consumer-resource interaction strengths may vary systematically across different habitat categories and consumer types.
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| 6. |
- Brose, Ulrich, et al.
(författare)
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Predicting the consequences of species lossusing size-structured biodiversity approaches
- 2017
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Ingår i: Biological Reviews. - : Wiley-Blackwell. - 1464-7931 .- 1469-185X. ; 92:2, s. 684-697
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Forskningsöversikt (refereegranskat)abstract
- Understanding the consequences of species loss in complex ecological communities is one of the great challenges in current biodiversity research. For a long time, this topic has been addressed by traditional biodiversity experiments. Most of these approaches treat species as trait-free, taxonomic units characterizing communities only by species number without accounting for species traits. However, extinctions do not occur at random as there is a clear correlation between extinction risk and species traits. In this review, we assume that large species will be most threatened by extinction and use novel allometric and size-spectrum concepts that include body mass as a primary species trait at the levels of populations and individuals, respectively, to re-assess three classic debates on the relationships between biodiversity and (i) food-web structural complexity, (ii) community dynamic stability, and (iii) ecosystem functioning. Contrasting current expectations, size-structured approaches suggest that the loss of large species, that typically exploit most resource species, may lead to future food webs that are less interwoven and more structured by chains of interactions and compartments. The disruption of natural body-mass distributions maintaining food-web stability may trigger avalanches of secondary extinctions and strong trophic cascades with expected knock-on effects on the functionality of the ecosystems. Therefore, we argue that it is crucial to take into account body size as a species trait when analysing the consequences of biodiversity loss for natural ecosystems. Applying size-structured approaches provides an integrative ecological concept that enables a better understanding of each species' unique role across communities and the causes and consequences of biodiversity loss.
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| 7. |
- Brose, Ulrich, et al.
(författare)
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Spatial aspects of food webs
- 2005
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Ingår i: Dynamic Food Webs. - London, UK : Elsevier. - 9780120884582 - 0120884585 ; , s. 463-469
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Konferensbidrag (refereegranskat)abstract
- Aspects of spatial scale have until recently been largely ignored in empirical and theoretical food web studies (e.g., Cohen & Briand 1984, Martinez 1992, but see Bengtsson et al. 2002, Bengtsson & Berg, this book). Most ecologists tend to conceptualize and represent food webs as static representations of communities, depicting a community assemblage as sampled at a particular point in time, or highly aggregated trophic group composites over broader scales of time and space (Polis et al. 1996). Moreover, most researchers depict potential food webs, which contain all species sampled and all potential trophic links based on literature reviews, several sampling events, or laboratory feeding trials. In reality, however, not all these potential feeding links are realized as not all species co-occur, and not all samples in space or time can contain all species (Schoenly & Cohen 1991), hence, yielding a variance of food web architecture in space (Brose et al. 2004). In recent years, food web ecologists have recognized that food webs are open systems – that are influence by processes in adjacent systems – and spatially heterogeneous (Polis et al. 1996). This influence of adjacent systems can be bottom-up, due to allochthonous inputs of resources (Polis & Strong 1996, Huxel & McCann 1998, Mulder & De Zwart 2003), or top-down due to the regular or irregular presence of top predators (e.g., Post et al. 2000, Scheu 2001). However, without a clear understanding of the size of a system and a definition of its boundaries it is not possible to judge if flows are internal or driven by adjacent systems. Similarly, the importance of allochthony is only assessable when the balance of inputs and outputs are known relative to the scale and throughputs within the system itself. At the largest scale of the food web – the home range of a predator such as wolf, lion, shark or eagle of roughly 50 km2 to 300 km2 –the balance of inputs and outputs caused by wind and movement of water may be small compared to the total trophic flows within the home range of the large predator (Cousins 1990). Acknowledging these issues of space, Polis et al (1996) argued that progress toward the next phase of food web studies would require addressing spatial and temporal processes. Here, we present a conceptual framework with some nuclei about the role of space in food web ecology. Although we primarily address spatial aspects, this framework is linked to a more general concept of spatio-temporal scales of ecological research.
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| 8. |
- Clough, Yann, et al.
(författare)
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Land-use choices follow profitability at the expense of ecological functions in Indonesian smallholder landscapes
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Smallholder-dominated agricultural mosaic landscapes are highlighted as model production systems that deliver both economic and ecological goods in tropical agricultural landscapes, but trade-offs underlying current land-use dynamics are poorly known. Here, using the most comprehensive quantification of land-use change and associated bundles of ecosystem functions, services and economic benefits to date, we show that Indonesian smallholders predominantly choose farm portfolios with high economic productivity but low ecological value. The more profitable oil palm and rubber monocultures replace forests and agroforests critical for maintaining above- and below-ground ecological functions and the diversity of most taxa. Between the monocultures, the higher economic performance of oil palm over rubber comes with the reliance on fertilizer inputs and with increased nutrient leaching losses. Strategies to achieve an ecological-economic balance and a sustainable management of tropical smallholder landscapes must be prioritized to avoid further environmental degradation.
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| 9. |
- Curtsdotter, Alva, et al.
(författare)
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Robustness to secondary extinctions: Comparing trait-based sequential deletions in static and dynamic food webs
- 2011
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Ingår i: Basic and Applied Ecology. - : Elsevier. - 1439-1791 .- 1618-0089. ; 12:7, s. 571-580
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Tidskriftsartikel (refereegranskat)abstract
- The loss of species from ecological communities can unleash a cascade of secondary extinctions, the risk and extent of which are likely to depend on the traits of the species that are lost from the community. To identify species traits that have the greatest impact on food web robustness to species loss we here subject allometrically scaled, dynamical food web models to several deletion sequences based on species’ connectivity, generality, vulnerability or body mass. Further, to evaluate the relative importance of dynamical to topological effects we compare robustness between dynamical and purely topological models. This comparison reveals that the topological approach overestimates robustness in general and for certain sequences in particular. Top-down directed sequences have no or very low impact on robustness in topological analyses, while the dynamical analysis reveals that they may be as important as high-impact bottom-up directed sequences. Moreover, there are no deletion sequences that result, on average, in no or very few secondary extinctions in the dynamical approach. Instead, the least detrimental sequence in the dynamical approach yields an average robustness similar to the most detrimental (non-basal) deletion sequence in the topological approach. Hence, a topological analysis may lead to erroneous conclusions concerning both the relative and the absolute importance of different species traits for robustness. The dynamical sequential deletion analysis shows that food webs are least robust to the loss of species that have many trophic links or that occupy low trophic levels. In contrast to previous studies we can infer, albeit indirectly, that secondary extinctions were triggered by both bottom-up and top-down cascades.
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| 10. |
- Curtsdotter, Alva, et al.
(författare)
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The interaction between species traits and community properties determine food web resistance to species loss
- 2014
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The ability to identify the ecosystems most vulnerable to species loss is fundamental for the allocation of conservation efforts. With this aim, the traits of keystone species have been investigated, as have the properties defining systems especially sensitive to species loss. However, these two have rarely been investigated in relation to each other. Here we show, that the traits of the species primarily lost act in conjunction with the properties of the food web from which it is lost, in determining the resistance of the system. We find that the extent of bottom-up extinction cascades is determined mainly by traits related to food web topology, while traits related to population dynamics govern the extent of top-down cascades. As different disturbances affect species with different traits, this interaction implies that the characteristics defining a sensitive community depend on the disturbance it is subjected to.
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