Data Supplement, Dunn et al., page 1
Data Supplement
The Sixth Mass (co)Extinction-Are Most Endangered Species Parasites and Mutualists?
Robert R. Dunn, Nyeema C. Harris, Robert K. Colwell, Lian Pin Koh, Navjot S. Sodhi
Supplement 1. Definitions of terms related to co-extinction.
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BOX: Definitions—The number of terms used to describe chains of extinction or coextinctions has continued to grow through time. For example, while one body of literature has considered secondary extinctions at local scales, another literature has considered coextinctions, typically at global scales. The two terms, however, are nearly or entirely synonymous. Here we offer brief definitions of the terms used in considering co-extinctions.
Co-extinction: Stork and Lyall (Stork & Lyal 1993) coined the term co-extinction to refer specifically to the extinction of host-specific parasites with the extinction of their hosts. The term has since been used more broadly to refer to the loss of one species as a result of the extinction of another species it depends on (e.g., Koh et al.
1994, Thacker et al.
2006).
Co-endangerment: Koh et al.
(2004) coined the term co-endangerment to refer to the endangerment of an affiliate (parasite, commensal, or mutualist) due to the endangerment of the species on which it depends.
Secondary extinctions: This term refers to extinctions of species due to the extinctions of species on which they depend. It appears to be synonymous with the current use of coextinction.
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Trophic cascade: The term originally referred loosely to the consequences at one trophic level of a change in the composition of species at another trophic level (Paine 1980). Other authors
(Pace 1999) prefer a more inclusive concept, referring to trophic cascades as "strong interactions within food webs that influence the properties of the system”—a definition broad enough to include some kinds of co-extinction.
Chains of extinction : Diamond (1989) appears to have introduced the term chains of extinction which, like co-extinction and secondary extinction, refers to additional extinctions that result from the extinction of some focal species. “Chains of extinction" however is broader in that it includes both co-extinctions and cases in which the loss of one species leads to increases in the abundance of other species and consequent ecological impacts.
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Supplement 2. Carnivore parasite data.
We conducted a systematic literature review to compile a list of parasites for each of 29 terrestrial, North American species of the order Carnivora (Table 1). We searched peerreviewed publications using several databases including the Global Mammal Parasites database, the Natural History Museum host-parasite database, and the Zoological Record.
The keywords used in the search included the common name or scientific name of each species and of each (ecto) parasite or disease. We included studies published from January
1965 through May 2008 and inclusively defined parasites to cover microparasites (viruses, bacteria, and protozoa), macroparasites (helminthes) and ectoparasites (arthropods). Parasites reported from experimental manipulations or captive individuals were not included in the analysis.
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Table 1
Common Name Scientific Name
Coyote
Gray wolf
Red wolf
Gray fox
Island gray fox
Arctic fox
Kit fox
Swift fox
Red fox
Canada lynx
Bobcat
Cougar
F AMILY C ANIDAE
Canis latrans
Canis lupus
Canis rufus
Urocyon cinereoargenteus
Urocyon littoralis
Vulpes lagopus
Vulpes macrotis
Vulpes velox
Vulpes vulpes
F
AMILY
F
ELIDAE
Lynx canadensis
Lynx rufus
Puma concolor
Hog-nosed skunk
Hooded skunk
Striped skunk
F AMILY M EPHITIDAE
Conepatus leuconotus
Mephitis macroura
Mephitis mephitis
Western spotted skunk Spilogale gracilis
Eastern spotted skunk Spilogale putorius
Wolverine
American Marten
Fisher
F AMILY M USTELIDAE
Gulo gulo
Martes americana
Martes pennanti
Ermine
Long-tailed weasel
Black-footed ferret
Mustela erminea
Mustela frenata
Mustela nigripes
Least weasel
American mink
American badger
Mustela nivalis
Mustela vison
Taxidea taxus
Raccoon
Black bear
Brown bear
F AMILY P ROCYONIDAE
Procyon lotor
F AMILY U RSIDAE
Ursus americanus
Ursus arctos
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Supplement 3. Estimates of the co-endangerment of plant parasites.
Plant parasites and co-extinction—The biggest determinant of the global magnitude of coextinction rates has to do not with the parasites of vertebrates, but instead with the parasites, commensals and mutualists of tropical plants. By most estimates, tropical affiliates, and in particular parasitic or herbivorous insects, account for most species on Earth (Stork 1988).
Yet there are still no consensus estimates of the average number of insect species found in a tropical tree, the average host specificity of those insects, or of the total number of tropical forest insect species on Earth (much less the rest of insect diversity). Perhaps the best studied region with regard to the diversity and host specificity of tropical herbivores is Papua New
Guinea, where herbivores appear to be relatively generalist, with species feeding, on average, on 4.3 (butterflies)-6.8 (beetles) host species (Koh et al.
2004; Novotny et al.
2002). Hubbell et al . (2008) predicted that at least 20% of Amazonian trees are at risk of extinction due solely to forest clearance. Based on the assumptions that other plants and thus the tropical forests they comprise are at similar risk of extinction, and that there are roughly 310,000 plant species (Koh et al 2004), we used the nomographic model of Koh et al . (2004), to calculate the expected percentage of herbivores (saying nothing of mutualists, commensals or other sorts of parasites) that are co-endangered to be between 6.1% (beetles) and 9.4% (butterfly).
Even if the diversity of herbivores is only two million species, this would mean that 123 to
188 thousand species of herbivores should be regarded as co-endangered. If, as some still argue, the diversity of tropical herbivores is closer to ten million species, these estimates increase fivefold—and so on for even higher estimates of herbivore diversity.
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Supplemental Literature Cited
Diamond, J. M. 1989 Overview of recent extinctions. . In Conservation for the Twenty-first
Century (ed. D. Western, Pearl, M.). Oxford: Oxford University Press.
Koh, L. P., Dunn, R. R., Sodhi, N. S., Colwell, R. K., Proctor, H. C. & Smith, V. S. 2004
Species coextinctions and the biodiversity crisis. Science 305 , 1632-1634.
Novotny, V., Basset, Y., Miller, S. E., Weiblen, G. D., Bremer, B., Cizek, L. & Drozd, P.
2002 Low host specificity of herbivorous insects in a tropical forest. Nature 416 , 841-
844.
Pace, M. L. A. A. 1999 Trophic cascades revealed in diverse ecosystems. Trends in Ecology and Evolution 14 , 483-488.
Paine, R. T. 1980 Food Webs: Linkage, Interaction Strength and Community Infrstructure.
Journal of Animal Ecology 49 , 667-685.
Stork, N. E. 1988 Insect diversity: facts, fiction and speculation. Biological Journal of the
Linnean Society 353 , 321-337.
Stork, N. E. & Lyal, C. H. C. 1993 Extinction or Co-Extinction Rates. Nature 366 , 307-307.
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