| 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. |
- 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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| 3. |
- Ohlsson, Mikael, 1983-
(författare)
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The significance of species groups for food web structure and functioning
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In ecosystems across the world, species co-exist, compete, and consume, all while adapting to environmental conditions and disruptions. An important key to the puzzle of understanding how species will respond to changes in the ecosystems, caused by for example climate change, pollution, habitat destruction, and overexploitation, is what current roles species have in a larger context. Species interactions are the basis for many ecological processes, for example, describing who eats whom in food webs. Finding groups of species that have similar interactions can provide insight into what roles species have in a food web, as well as identify core structures and functions of said food webs. Food webs are often based on data aggregates of large areas. Consequently, there is a possibility of blurring local aspects of the food web structure, thus blurring locally realized species roles. In Paper I, I used the group model to analyze local and regional group structures of a food web in the Barents Sea. The group model identifies groups linked to their niche, in which species eat, and are eaten by similar species. I found the large, regional food web diverged from the local group structures, indicating that locally scaled food webs may be required to find more accurately realized species roles. On a local scale, similar group structures were generally spatially clustered and environmentally similar. This was to some extent explained by similarities in species compositions, but more fine-grained patterns related to species identities further impacted the group structures. In essence, the group model is a type of community detection based on stochastic block models. Generated groups contain groups of species with similar sets of prey and predators. Groups are related to both trophic similarity and modularity, but the process itself is, as the name implies, stochastic. Various methodologies to determine a "best fit" group structure out of multiple iterations exist. Arguments can however be made, that discarded, alternative group structures may still hold ecological relevance. In Paper II, I investigated five food webs by creating a solution landscape from their respective alternative group structures. My results showed, that the core group structure remained intact across alternative solutions, while potential changes in the group structure were generally limited to smaller subsets of groups or species. Expanding on the analysis of Paper II, Paper III, accounts for the inherent un-certainty of interactions in food webs. Food webs are based on data sets, potentially covering hundreds of species and thousands of interactions. How-ever, spatial and temporal aspects, and the dynamical nature of whether interactions are realized, can impact the food web structure. Here, I investigated how group structures responded to disturbing interactions (i.e., random removal of different fractions). The key findings showed how in general, core group structures remained intact, and already unstable groups turned increasingly unstable. Species traits distinctly defined group identities, but I found no particular species traits ubiquitously linked to unstable group structures. How species interact is intrinsic to their traits; basic trait-matching constraints must be fulfilled for an interaction to be realized, such as a predator being large enough to eat a specific prey. Traits are however also subject to change, with potentially strong selective pressures from for example environmental change or overexploitation. If traits change sufficiently, species interactions can also change, potentially putting affected species in a new ecological context with new predators, prey, and competitive relationships. Possibly related, the cod population in the Baltic Sea, has failed to recover even after ceasing fishing. In Paper IV, I formulated an eco-evolutionary model, which considered cod’s changed ecological role after the collapse, highlighting how competition with flounder species can contribute to blocking the cod population in the Baltic Sea from recovering. With this thesis, I aimed to improve understanding of how species groups based on interactions relate to food web structure. My results highlight how the group model can generate robust groups, which are generally resilient to even moderate disturbances while providing a coarse-grained representation of species roles in a food web. The spatial context of the food web, with its included species and interactions, needs to be considered to get a more accurate representation of locally realized species roles. I have further modeled how species traits may be altered by eco-evolutionary dynamics under strong selective pressure, with subsequent shifts in ecological roles. These aspects are pivotal in understanding how species in our ecosystems will be affected by today’s multitude of environmental impacts.
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