| 1. |
- Curtsdotter, Alva, et al.
(författare)
-
Robustness to secondary extinctions: Comparing trait-based sequential deletions in static and dynamic food webs
- 2011
-
Ingår i: Basic and Applied Ecology. - : Elsevier. - 1439-1791 .- 1618-0089. ; 12:7, s. 571-580
-
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.
|
|
| 2. |
- Eklöf, Anna, et al.
(författare)
-
The dimensionality of ecological networks
- 2013
-
Ingår i: Ecology Letters. - : Blackwell Publishing. - 1461-023X .- 1461-0248. ; 16:5, s. 577-583
-
Tidskriftsartikel (refereegranskat)abstract
- How many dimensions (trait-axes) are required to predict whether two species interact? This unansweredquestion originated with the idea of ecological niches, and yet bears relevance today for understanding whatdetermines network structure. Here, we analyse a set of 200 ecological networks, including food webs,antagonistic and mutualistic networks, and find that the number of dimensions needed to completelyexplain all interactions is small ( < 10), with model selection favouring less than five. Using 18 high-qualitywebs including several species traits, we identify which traits contribute the most to explaining networkstructure. We show that accounting for a few traits dramatically improves our understanding of the structureof ecological networks. Matching traits for resources and consumers, for example, fruit size and billgape, are the most successful combinations. These results link ecologically important species attributes tolarge-scale community structure.
|
|
| 3. |
- Kaneryd, Linda, et al.
(författare)
-
Species-rich ecosystems are vulnerable to cascading extinctions in an increasingly variable world
- 2012
-
Ingår i: Ecology and Evolution. - : Wiley-Blackwell. - 2045-7758. ; 2:4, s. 858-874
-
Tidskriftsartikel (refereegranskat)abstract
- Global warming leads to increased intensity and frequency of weather extremes. Such increased environmental variability might in turn result in increased variation in the demographic rates of interacting species with potentially important consequences for the dynamics of food webs. Using a theoretical approach, we here explore the response of food webs to a highly variable environment.We investigate how species richness and correlation in the responses of species to environmental fluctuations affect the risk of extinction cascades. We find that the risk of extinction cascades increases with increasing species richness, especially when correlation among species is low. Initial extinctions of primary producer species unleash bottom-up extinction cascades, especially in webs with specialist consumers. In this sense, species-rich ecosystems are less robust to increasing levels of environmental variability than species-poor ones. Our study thus suggests that highly speciesrich ecosystems such as coral reefs and tropical rainforests might be particularly vulnerable to increased climate variability.
|
|
| 4. |
|
|
