| 1. |
- 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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| 2. |
- 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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| 3. |
- Riede, James O., et al.
(författare)
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Stepping in Elton's footprints: a general scaling model for body masses and trophic levels across ecosystems
- 2011
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Ingår i: Ecology Letters. - : Wiley-Blackwell. - 1461-023X .- 1461-0248. ; 14:2, s. 169-178
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Despite growing awareness of the significance of body-size and predator–prey body-mass ratios for the stability of ecological networks,our understanding of their distribution within ecosystems is incomplete. Here, we study the relationships between predator and prey size,body-mass ratios and predator trophic levels using body-mass estimates of 1313 predators (invertebrates, ectotherm and endothermvertebrates) from 35 food-webs (marine, stream, lake and terrestrial). Across all ecosystem and predator types, except for streams (whichappear to have a different size structure in their predator–prey interactions), we find that (1) geometric mean prey mass increases withpredator mass with a power-law exponent greater than unity and (2) predator size increases with trophic level. Consistent with ourtheoretical derivations, we show that the quantitative nature of these relationships implies systematic decreases in predator–prey bodymassratios with the trophic level of the predator. Thus, predators are, on an average, more similar in size to their prey at the top of foodwebsthan that closer to the base. These findings contradict the traditional Eltonian paradigm and have implications for our understandingof body-mass constraints on food-web topology, community dynamics and stability.
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