COS 72-10 - Species loss initiates multifaceted and cascading instability in a natural food web

Wednesday, August 10, 2011: 4:40 PM
6A, Austin Convention Center
Ian Donohue1, Nessa E. O'Connor2 and Mark C. Emmerson2, (1)School of Natural Sciences, Trinity College Dublin, Dublin, Ireland, (2)School of Biological Sciences, Queen's University Belfast, Belfast, Northern Ireland

Theory predicts that the loss of species destabilizes food webs, reducing their ability to resist perturbations and increasing susceptibility to further species losses. However, existing theoretical models of species extinctions focus largely on predator-prey trophic interaction networks, omitting potentially critical information on the non-trophic and indirect interactions that can comprise key drivers of community dynamics. There is, therefore, a need to test theoretical predictions of the effects of species loss on stability in natural ecosystems because they incorporate natural environmental variance and contain established assemblages structured by a diverse range of interactions.


Here we show, by simulating species extinctions experimentally across multiple trophic levels on a rocky shore, that predator species loss triggers rapidly cascading instability in real food webs. However, the nature of the instability was determined both by the identity of the predator and the structure of intermediate trophic levels, while the loss of primary consumers destabilized producer assemblages in still different ways. Thus, different components of biodiversity regulate stability in distinct ways. We also found that reductions in some forms of stability after species loss were up to an order of magnitude greater than theoretical predictions. We conclude that, by focusing on trophic interactions and single forms of stability in isolation, we have been underestimating significantly the overall destabilizing effect of biodiversity loss and thus the true scale of the extinction crisis that we face.

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