Illinois Natural History Survey Reports

              1
I LLINOIS
NATURAL
HI STORY
S U R V E Y R e p o r t s
November/
December 1998
No. 354
I N S I D E Illinois Under Siege
Great Lakes Invasion
2
The Bighead Carp
3
Zebra Mussel/Unionid
Interactions
4
The Round Goby
6
Successful Management
of the Imported Crucifer
Weevil
8
Status and Distribution
of Daphnia lumholtzi
9
The Rusty Crayfi sh in
Illinois
10
Good Beetle, Bad Plant
12
Bad Beetle Finds A
Good Home
13
Mosquito Marauders
14
The Beetle That Tried to
Steal Christmas
15
Garlic Mustard: A Stink-ing
Invasive Weed
16
The Naturalist’s
Apprentice:
What is a Pest?
18
Continued on back page
This issue of Illinois
Natural History
Survey Reports is
devoted to a single
topic—invasive spe-cies.
Because we
consider this topic
so important and
because there are
many invasive spe-cies
in Illinois, this
issue is more than
twice as large as
previous ones so that
we can adequately
cover the topic. Even
our school activities
column, “The Natu-ralist’s
Apprentice,”
is designed to help
answer the question,
What is a pest?
Each new inva-sive
species receives
a moment of media
attention, then fades
from public notice.
Such intermittent
publicity masks
a general pattern
that should concern
everyone: Because
new species are introduced almost
every year but we seldom are able
to completely eradicate them, the
total number of invasive species is
increasing. Approximately one-third
of the plants you are likely to
see in most woodlands, wetlands,
and grasslands in Illinois are
non-native species. In the aquatic
realm, the Great Lakes illustrate
virtually every problem associ-ated
with transfers of species by
humans, culminating in an altered
ecosystem that no longer maintains
itself but requires costly human
intervention. The invasive species
described in these articles are only
a few of the more recent introduc-tions
that Survey scientists are
seeking to control.
What is an invasive species?
There are at least 4,500 known spe-cies
of foreign origin
that have established
free-living populations
in the U.S. Some of
these are benefi cial
animals and plants that
were intentionally in-troduced,
such as cattle
and wheat, and are
not considered prob-lems.
There are others,
however, that displace
benefi cial native spe-cies,
carry diseases and
parasites that threaten
human health and the
health of domesticated
and native species, and
cause economic damage
(e.g., the zebra mussel
clogs water intakes of
industrial and munici-pal
water plants). Not
every species that is
introduced to the U.S.
survives and estab-lishes
self-maintaining
populations. The terms
“invasive” or “weedy”
are generally used for
species that out-com-pete
and displace native
species, often becoming the
dominant species, not just in
a numerical sense, but also
in terms of altering envi-ronmental
conditions. For
example, dense beds of zebra
mussels can use up enough
oxygen in rivers to stress not
only themselves but also na-