title: Trophically unique species are vulnerable to cascading extinction.
abstract: Understanding which species might become extinct and the consequences of such loss is critical. One consequence is a cascade of further, secondary extinctions. While a significant amount is known about the types of communities and species that suffer secondary extinctions, little is known about the consequences of secondary extinctions for biodiversity. Here we examine the effect of these secondary extinctions on trophic diversity, the range of trophic roles played by the species in a community. Our analyses of natural and model food webs show that secondary extinctions cause loss of trophic diversity greater than that expected from chance, a result that is robust to variation in food web structure, distribution of interactions strengths, functional response, and adaptive foraging. Greater than expected loss of trophic diversity occurs because more trophically unique species are more vulnerable to secondary extinction. This is not a straightforward consequence of these species having few links with others but is a complex function of how direct and indirect interactions affect species persistence. A positive correlation between a species' extinction probability and the importance of its loss defines high-risk species and should make their conservation a priority.
authors.affiliation: Department of Animal and Plant Sciences, Alfred Denny Building, University of Sheffield, Western Bank, Sheffield S10 2TN, United Kingdom. o.petchey@shef.ac.uk
authors.forename: Owen L
authors.initials: OL
authors.lastname: Petchey
authors.forename: Anna
authors.initials: A
authors.lastname: Eklöf
authors.forename: Charlotte
authors.initials: C
authors.lastname: Borrvall
authors.forename: Bo
authors.initials: B
authors.lastname: Ebenman
mesh_terms: D044822:Biodiversity; D003198:Computer Simulation; D003247:Conservation of Natural Resources / Q000379:methods*; D017753:Ecosystem; D053476:Extinction, Biological; D020387:Food Chain; D008962:Models, Theoretical; D013045:Species Specificity