Biological Invasions (2009) 11, 2341-2350

Randall S. Morin, Andrew M. Liebhold and Kurt W. Gottschalk (2009)
Anisotropic spread of hemlock woolly adelgid in the eastern United States
Biological Invasions 11 (10), 2341-2350
Abstract: Simple population models predict that the spread of an invading species through a homogenous habitat should be equal in all directions, but geographic variation in the habitat that affects either reproduction or movement could result in variable rates of spread. We analyse records of the historical range expansion of the hemlock woolly adelgid (HWA) (Adelges tsugae Annand) in the eastern United States from 1951 to 2006 to document that this species has spread in an anisotropic fashion. Furthermore, the magnitude and direction of this anisotropy has varied through time. We explore the extent to which this spatial and temporal variation in spread can be explained by geographical variation in climate and by the abundance of hosts, eastern hemlock (Tsuga canadensis L.) and Carolina hemlock (Tsuga caroliniana Engelm.). We found that a significant component of the spatial anisotropy in HWA spread rate can be explained by the geographical distribution of host trees. January temperatures were negatively associated with spread rates but this may be an artifact of the association between hemlock and cold climates. The current distribution of the adelgid in eastern N. America may be approaching the extent of its potential range to the south and west determined by availability of host hemlock and to the north determined by lethal cold winter temperatures.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Randall S. Morin, Andrew M. Liebhold

Research topic(s) for pests/diseases/weeds:
population dynamics/ epidemiology
surveys/sampling/distribution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Adelges tsugae	Hemlock (Tsuga)	U.S.A. (NE)
	Adelges tsugae	Hemlock (Tsuga)	U.S.A. (SE)