Node-by-node disassembly of a mutualistic interaction web driven by species introductions

Interactionwebs summarize the diverse interactionsamong species in communities. The addition or loss of particular species and the alteration of key interactionscan lead to the disassemblyof the entire interactionweb, although the nontrophic effects of species loss on interactionwebs are poorly understood. We took advantage of ongoing invasions by a suite of exotic species to examine their impact in terms of the disassemblyof an interactionweb in Patagonia, Argentina. We found that the reduction of one species (a host of a keystone mistletoe species) resulted in diverse indirect effectsthat led to the disassemblyof an interactionweb through the loss of the mistletoe, two key seed-dispersers(a marsupialand a bird), and a pollinator ( hummingbird). Our results demonstrate that the gains and losses of species are both consequences and drivers of global changethat can lead to underappreciated cascading coextinctionsthrough the disruption of mutualisms.