How invasive bugs get that way Manipulation of soil communities enables some introduced species to
turn into 'monsters' By Stuart Blackman
While most introduced species never become established, some "have just gone crazy [and] changed,
from being nice guys-good citizens coexisting with other species-into these competitive monsters,"
according to University of Montana plant ecologist Ragan Callaway. One secret to invasive species'
success is a knack for manipulating soil organisms in their adoptive habitat to their own advantage,
according to a paper by Callaway and colleagues in the February 19 Nature (Nature, 427:731-733,
February 19, 2004).
The "competitive monster" studied by Callaway and colleagues was spotted knapweed (Centaurea
maculosa), a European native that has spread to all 50 US states since its introduction in the late
1800s. They took a biogeographic approach, comparing the feedback effects that arise between the
plant and soil microbes when it is grown in soil taken from its native versus adoptive habitat.
The authors showed that soil microbes from the plant's home range have stronger inhibitory effects
on its growth than do those from its US habitat. Sterilization of European soil resulted in a 166%
increase in plant biomass compared with a 24% increase following the same treatment of soil from
Montana. Additionally, plants grown in nonsterilized European soil were smaller if the soil had been
precultured with other C. maculosa plants rather than a European grass species. Conversely, in
Montana soil, plants did better in C. maculosa-primed soil.
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Posted by Robert Karl Stonjek.