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Research:

Interaction between propagule pressure and urban tree cover in the establishment of exotic pests

Investigators: Manuel Colunga-Garcia, Robert Haack, Roger Magarey, and Margaret Margosian.

Published in: Journal of Economic Entomology 103 (1): 108-118.(PDF version)

Funding acknowledgement: NRI-USDA/CSREES 2006-55605-166.58

Abstract: As international trade increases so does the prominence of urban areas as gateways for exotic forest insects (EFI). Delimiting hot spots for invasions (i.e., areas where establishment is likely) within urban areas would facilitate monitoring efforts.

We used a propagule-pressure framework to delimit establishment hot spots of a hypothetical generalist EFI in six U.S. urban areas: Chicago, Detroit, Houston, Los Angeles-Long Beach-Santa Ana, New York-Newark, and Seattle. We assessed how urban tree cover and propagule pressure interact to delimit establishment hot spots and compared the location of these hot spots with actual recent U.S. detections of two EFI: the Asian strain of the gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), and Asian longhorned beetle, Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae). Using a lattice of 5-km-diameter cells for each urban area, we used the input data (urban tree cover and propagule pressure) to model establishment and Moran's I to delimit hot spots. We used urban population size and the area of commercial-industrial land use as indicators of propagule pressure in the model.

Relative establishment of EFI was influenced more by the two propagule pressure indicators than by tree cover. The delimited land use-based hot spots for Los Angeles-Long Beach-Santa Ana and New York-Newark encompassed more of the actual detections of the Asian gypsy moth and Asian longhorned beetle, respectively, than the population-based hot spots. No significant difference occurred between hot spot types for Asian longhorned beetle detections in the Chicago urban area.

 

Trade Commodity Tons

Distribution of tree cover, two propagule pressure indicators (population-based, and land use-based), and relative establishment hot spots for a hypothetical generalist forest pest that could be introduced in the urban area of Chicago via imported cargo. (click the image for an enlarged version).

 

Trade Commodity Tons

Distribution of tree cover, two propagule pressure indicators (population-based, and land use-based), and relative establishment hot spots for a hypothetical generalist forest pest that could be introduced in the urban area of Detroit via imported cargo. (click the image for an enlarged version).

     
     

Trade Commodity Tons

Distribution of tree cover, two propagule pressure indicators (population-based, and land use-based), and relative establishment hot spots for a hypothetical generalist forest pest that could be introduced in the urban area of Houston via imported cargo. (click the image for an enlarged version).

 

Trade Commodity Tons

Distribution of tree cover, two propagule pressure indicators (population-based, and land use-based), and relative establishment hot spots for a hypothetical generalist forest pest that could be introduced in the urban area of Los Angeles/Long Beach/Santa Anna via imported cargo. (click the image for an enlarged version).

     
     

Trade Commodity Tons

Distribution of tree cover, two propagule pressure indicators (population-based, and land use-based), and relative establishment hot spots for a hypothetical generalist forest pest that could be introduced in the urban area of New York/Newark via imported cargo. (click the image for an enlarged version).

 

Trade Commodity Tons

Distribution of tree cover, two propagule pressure indicators (population-based, and land use-based), and relative establishment hot spots for a hypothetical generalist forest pest that could be introduced in the urban area of Seattle via imported cargo. (click the image for an enlarged version).

     
     

Trade Commodity Tons

Establishments/detections of three exotic forest insects in four urban areas in relation to population-based and land use-based hot spots (gray, hot spot sites; red, establishment/detection within a hot spot: blue, establishment/detection outside a hot spot) (click the image for an enlarged version).

 

 

 

[ Last updated: May 3, 2010 ]

 

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