Biology Reference
In-Depth Information
Crawley 2002). A surprising number of specialist herbivores were found
to use alien plants, but their impact was small. In all but two studies, gen-
eralist impacts were lighter on alien than on native plants.
A recent study provides a good example of release from herbivores and
disease agents. White campion (
Silene latifolia
) is a European weed intro-
duced to North America in the mid-1800s. It is now widespread, occur-
ring in 43 states and several Canadian provinces, and in some areas is con-
sidered a noxious weed.Wolfe (2002) examined 50 populations in Europe
and 36 in North America, recording the presence or absence of phloem-
feeding aphids, anther smut fungi, herbivore damage to the flowers, and
fruit or seed predation.The results (fig. 7.2) showed that all forms of her-
bivore and fungal damage were much more frequent in Europe than in
North America. Overall, the frequency of damage was 17 times as great
Figure 7.2.
Frequency of occurrence of phloem-feeding aphids, anther smut fungi,
flower herbivory, and fruit or seed predation in populations of
Silene latifolia
in
Europe and North America. (Reprinted with permission from L. M. Wolfe. 2002.
Why alien invaders succeed: support for the escape-from-enemy hypothesis.
Ameri-
can Naturalist
160:705-711. © 2002 University of Chicago Press.)
