| 2. |
- Petchey, Owen L., et al.
(författare)
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Trophically Unique Species Are Vulnerable to Cascading Extinction
- 2008
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Ingår i: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 171:5, s. 568-579
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Tidskriftsartikel (refereegranskat)abstract
- Understanding which species might become extinct and the consequences of such loss is critical. One consequence is a cascade of further, secondary extinctions. While a significant amount is known about the types of communities and species that suffer secondary extinctions, little is known about the consequences of secondary extinctions for biodiversity. Here we examine the effect of these secondary extinctions on trophic diversity, the range of trophic roles played by the species in a community. Our analyses of natural and model food webs show that secondary extinctions cause loss of trophic diversity greater than that expected from chance, a result that is robust to variation in food web structure, distribution of interactions strengths, functional response, and adaptive foraging. Greater than expected loss of trophic diversity occurs because more trophically unique species are more vulnerable to secondary extinction. This is not a straightforward consequence of these species having few links with others but is a complex function of how direct and indirect interactions affect species persistence. A positive correlation between a species’ extinction probability and the importance of its loss defines high-risk species and should make their conservation a priority.
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| 3. |
- Yvon-Durocher, Gabriel, et al.
(författare)
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Across ecosystem comparisons of size structure: methods, approaches and prospects
- 2011
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Ingår i: OIKOS. - : Nordic Ecological Society. - 0030-1299. ; 120:4, s. 550-563
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Tidskriftsartikel (refereegranskat)abstract
- Understanding how ecological communities are structured and how this may vary between different types of ecosystems is a fundamental question in ecology. We develop a general framework for quantifying size-structure within and among different ecosystem types (e. g. terrestrial, freshwater or marine), via the use of a suite of bivariate relationships between organismal size and properties of individuals, populations, assemblages, pair-wise interactions, and network topology. Each of these relationships can be considered a dimension of size-structure, along which real communities lie on a continuous scale. For example, the strength, slope, or elevation of the body mass-versus-abundance or predator size-versus-prey size relationships may vary systematically among ecosystem types. We draw on examples from the literature and suggest new ways to use allometries for comparing among ecosystem types, which we illustrate by applying them to published data. Finally, we discuss how dimensions of size-structure are interconnected and how we could approach this complex hierarchy systematically. We conclude: (1) there are multiple dimensions of size-structure; (2) communities may be size-structured in some of these dimensions, but not necessarily in others; (3) across-system comparisons via rigorous quantitative statistical methods are possible, and (4) insufficient data are currently available to illuminate thoroughly the full extent and nature of differences in size-structure among ecosystem types.
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