Biology Reference
In-Depth Information
but only a few native insects attack the tree in Florida (Simberloff et al.
1997). In Australia, these herbivores substantially reduce the growth of
paperbarks (Balciunas and Burrows 1993).
Alien plants belonging to families that are not represented in the
region of introduction are especially impoverished in native herbivore
colonizers.
Opuntia
cacti introduced to South Africa, for example, have
not acquired any native herbivorous arthropods even after 250 yr (Moran
1980). American mangrove (
Rhizophora mangle
), introduced to Hawaii in
1902, lacks lepidopteran herbivores there, although several such species
attack the plant in Florida (Connor et al. 1980).Trees of the genera
Euca-
lyptus
and
Casuarina
introduced into various world regions from their
home in Australasia likewise have very depauperate faunas of herbivorous
arthropods (see, e.g., Ohmart and Edwards 1991). About 90 species of
woody plants of the genus
Eucalyptus
have been introduced into North
America (Paine and Millar 2002), beginning in the 1800s. Until recently,
these plants were almost completely free of herbivorous insects and plant
diseases. Few native insects have proven able to feed on eucalypts, and
only since 1984 have pest insects invaded from Australia.About 15 species
have now become established in California.
Accumulation of Predators and Parasitoids
by Alien Animals
Introduced arthropods also tend to acquire predators and parasites from
the native fauna of the new region. Several studies have been made of the
acquisition of parasitoids by alien arthropods. Parasitoids, like herbivorous
arthropods, vary from being highly host-specific to having a very wide
host range. Species of parasitoids that are closely adapted to host physiol-
ogy, so that the host continues to be active and feed for some time, tend
to be more host-specific (Askew and Shaw 1986).
The speed with which parasitoids can become associated with new
alien hosts is illustrated by a study of two recently introduced leaf-mining
moth species in England (Godfray et al. 1995).These moths, belonging to
the genus
Phyllonorycter
,were native to continental Europe. One species,
first noted in 1989, attacked garden shrubs of the genus
Pyracantha
, itself
an alien plant.The second, seen first in 1990, attacked species of sycamore
or plane tree (
Platanus
spp.). Data on the parasitoids associated with these
moths were collected from 1991 to 1993, just a few years after they had
been first noted.The parasitoids associated with these species were com-
