@article{BinzerBroseCurtsdotteretal.2011, author = {Binzer, Amrei and Brose, Ulrich and Curtsdotter, Alva and Ekloef, Anna and Rall, Bjoern C. and Riede, Jens O. and de Castro, Francisco}, title = {The susceptibility of species to extinctions in model communities}, series = {Basic and applied ecology : Journal of the Gesellschaft f{\"u}r {\"O}kologie}, volume = {12}, journal = {Basic and applied ecology : Journal of the Gesellschaft f{\"u}r {\"O}kologie}, number = {7}, publisher = {Elsevier}, address = {Jena}, issn = {1439-1791}, doi = {10.1016/j.baae.2011.09.002}, pages = {590 -- 599}, year = {2011}, 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.}, language = {en} } @article{RiedeBinzerBroseetal.2011, author = {Riede, Jens O. and Binzer, Amrei and Brose, Ulrich and de Castro, Francisco and Curtsdotter, Alva and Rall, Bjoern C. and Ekloef, Anna}, title = {Size-based food web characteristics govern the response to species extinctions}, series = {Basic and applied ecology : Journal of the Gesellschaft f{\"u}r {\"O}kologie}, volume = {12}, journal = {Basic and applied ecology : Journal of the Gesellschaft f{\"u}r {\"O}kologie}, number = {7}, publisher = {Elsevier}, address = {Jena}, issn = {1439-1791}, doi = {10.1016/j.baae.2011.09.006}, pages = {581 -- 589}, year = {2011}, abstract = {How ecological communities react to species extinctions is a long-standing yet current question in ecology. The species constituting the basic units of ecosystems interact with each other forming complex networks of trophic relationships and the characteristics of these networks are highly important for the consequences of species extinction. Here we take a more general approach and analyze a broad range of network characteristics and their role in determining food web susceptibility to secondary extinctions. We extend previous studies, that have focused on the consequences of topological and dynamical food web parameters for food web robustness, by also defining network-wide characteristics depending on the relationships between the distribution of species body masses and other species characteristics. We use a bioenergetic dynamical model to simulate realistically structured model food webs that differ in their structural and dynamical properties as well as their size structure. In order to measure food web robustness we calculated the proportion of species going secondarily extinct. A multiple regression analysis was then used to fit a general model relating the proportion of species going secondarily extinct to the measured food web properties. Our results show that there are multiple factors from all three groups of food web characteristics that affect food web robustness. However, we find the most striking effect was related to the body mass abundance relationship which points to the importance of body mass relationships for food web stability.}, language = {en} } @article{CurtsdotterBinzerBroseetal.2011, author = {Curtsdotter, Alva and Binzer, Amrei and Brose, Ulrich and de Castro, Francisco and Ebenman, Bo and Ekloef, Anna and Riede, Jens O. and Thierry, Aaron and Rall, Bjoern C.}, title = {Robustness to secondary extinctions comparing trait-based sequential deletions in static and dynamic food webs}, series = {Basic and applied ecology : Journal of the Gesellschaft f{\"u}r {\"O}kologie}, volume = {12}, journal = {Basic and applied ecology : Journal of the Gesellschaft f{\"u}r {\"O}kologie}, number = {7}, publisher = {Elsevier}, address = {Jena}, issn = {1439-1791}, doi = {10.1016/j.baae.2011.09.008}, pages = {571 -- 580}, year = {2011}, 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.}, language = {en} }