Biology Reference
In-Depth Information
Table 17.1.
Biological agents introduced to control target plants and their use of
nontarget plant species in the United States and the Caribbean region in relation to
presence or absence of congeners. (Data from Pemberton 2000.)
T
ARGET PLANTS WITH CONGENERS
T
ARGET PLANTS LACKING CONGENERS
Agents
Total
Agents
Total
adopting nontarget
adopting nontarget
Total BC
nontarget
plants
Total BC
nontarget
plants
agents released
plants
attacked
agents released
plants
attacked
U.S. Mainland
56
10
37
12
0
0
and Caribbean
Hawaii
5
4
3
49
1
1
shift is incidental, resulting from high populations of the biocontrol
species on the target host that cause individuals to move to other species
on which they cannot complete their life cycle (Blossey et al. 2001). In
many other cases, the shift is to plants or animals on which the biocon-
trol species can reproduce. For the United States mainland, Hawaii, and
the Caribbean region, Pemberton (2000) listed 15 species of herbivorous
biocontrol insects that have extended their feeding habits to 41 species of
native plants; in almost all cases, the extension species were close relatives
of the target plant (table 17.1).The plants involved included shrubs, cacti,
broad-leaved herbs, and flatsedges (
Cyperus
spp.). McFadyen (1998) and
Dennill et al. (1993) noted additional examples from other world regions.
Similar shifts have occurred for biocontrol agents of animal pests. For
parasitoids introduced to North America for control of insect pests,
Hawkins and Marino (1997) found that 51 (16.3%) of the 313 introduced
species were recorded from nontarget hosts. For Hawaii, 37 (32.2%) of
115 parasitoid species were noted to use nontarget hosts (Funasaki et al.
1988). In some cases, a single biocontrol parasitoid can attack many non-
target species. The parasitoid fly
Compsilura concinnata
was introduced for
biological control of gypsy moth (
Lymantria dispar
) from 1906 through
1986 (Boettner et al. 2000). This parasitoid attacks many nontarget host
moths in New England, including several Saturniid silk moths, the pop-
ulations of which have declined substantially or been extirpated in some
areas. In particular, wild populations of one silk moth,
Hemileuca maia
,a
species listed as threatened in Massachusetts, were found to be severely
affected by the parasitoid fly. In New Zealand, an introduced parasitoid
was found to attack 13 species of nontarget beetles (Samways 1997).
