Galatowitsch, S.M., N.O. Anderson, and P.D. Ascher, 1999. Invasiveness in
Wetland Plants in Temperate North America, University of Minnesota.
Reprinted from Wetlands (1999) 19(4): 733-755
Invasiveness in Wetland Plants in Temperate North America
Abstract
The spread of invasive taxa, including Lythrum salicaria, Typha x glauca,
Myriophyllum spicatum, Phalaris arundinacea, and Phragmites australis, has
dramatically changed the vegetation of many wetlands of North America. Three
theories have been advanced to explain the nature of plant invasiveness.
Aggressive growth during geographic expansion could result because 1) growth is
more favorable under new environmental conditions than those of resident locales
(environmental constraints hypothesis); 2) herbivores may be absent in the new
locale, resulting in selection of genotypes with improved competitive ability
and reduced allocation to herbivore defenses (evolution of increased competitive
ability hypothesis); and 3) interspecific hybridization occurred between a new
taxon and one existing in an area, resulting in novel phenotypes with selective
advantages in disturbed sites or phenotypes that can grow under conditions not
favorable for either parent (introgression hybrid speciation hypothesis). A
review of published literature found few studies that compare the growth and
dynamics of invasive populations in their new range versus those in historic
ranges. However, there is evidence that hydrologic alterations could facilitate
invasions by Typha x glauca and Phalaris arundinacea and that increased salinity
promoted spread of Typha angustifolia (parental taxon) and Phragmites
australis.
The potential for reduced herbivory causing aggressive growth is greatest for
Lythrum salicaria. Introgressive hybridization is potentially a cause of
invasiveness for all five species but has been established only for Typha x
glauca and Lythrum salicaria.
Contact: Susan Galatowitsch, University of Minnesota, Department of
Horticultural Science, 305 Alderman Hall, St Paul, MN 55108
Key Words: Purple_loosestrife, Aquatic_plant_management, Environmental_impacts
Product Type: Research,
Impact
User Type: Resource Management
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