<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">DEPARTMENT OF COMPUTER SCIENCE<div><br class="webkit-block-placeholder"></div><div>UNIVERSITY OF CHICAGO</div><div><br class="webkit-block-placeholder"></div><div>Date: Thursday, April 17, 2008</div><div>Time: 2:30 p.m.</div><div>Place: KPTC 120</div><div><br class="webkit-block-placeholder"></div><div>----------------------------------------------------------</div><div><br class="webkit-block-placeholder"></div><div>Speaker:<span class="Apple-tab-span" style="white-space: pre; "> </span>Stefano Allesina</div><div><br class="webkit-block-placeholder"></div><div>From:<span class="Apple-tab-span" style="white-space: pre; "> </span>NCEAS</div><div><br class="webkit-block-placeholder"></div><div>Web page:<span class="Apple-tab-span" style="white-space: pre; "> </span><span class="Apple-style-span" style="color: rgb(0, 0, 255); "><a href="http://web.mit.edu/jakebeal/www/">www.nceas.ucsb.edu/~allesina</a></span></div><!--StartFragment-->
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<div><br class="webkit-block-placeholder"></div><div>Title: Stability in Ecological Networks: Large Effects of Small Motifs</div><div><br class="webkit-block-placeholder"></div><div>Abstract: Large number of species interact and coexist in the intricate networks of consumer–resource interactions known as food webs. For decades ecologists held the view that more complex ecosystems, those with a larger number of species and connections, were also more likely to be persistent, explaining therefore the extremely high biodiversity we observe in nature. Robert May's mathematical argument on stability, however, proved that large, complex networks of ecological interactions with random structure tend invariably to instability. This result ignited the "complexity-stability" debate that has been one of the main drivers of theoretical ecology for three decades. Here we revisit May's argument and show that, when species interact as predators and prey, systems as complex as the ones observed in nature can still be stable. Moreover, stability is highly robust to perturbations of interaction strength, and is largely a property of structure driven by predator–prey loops. The results highlight the role of small modules for the persistence of large networks, so that the stability of small motifs can cascade in that of the whole network.</div><p class="MsoNormal">---------------------------------------------------------</p><p class="MsoNormal">Host:<span class="Apple-tab-span" style="white-space: pre; "> </span>Nina Hinrichs</p></body></html>