Biology Reference
In-Depth Information
genus
Monopterus
that are native to southern and eastern Asia, the East
Indies, and West Africa. During the 1990s, isolated populations of intro-
duced animals were discovered near Atlanta, Georgia, and Tampa, Miami,
and Homestead, Florida. These fish pose a very serious threat to native
wetland vertebrates of all types. The alien populations were provisionally
identified as the Asian swamp eel (
Monopterus albus
), a widely distributed
form of southern and eastern Asia for which considerable uncertainty
exists about systematics and taxonomy. Analyses of mtDNA sequences of
eels from North American and Asian localities indicated that at least three
independent introductions to North America had occurred (Collins et al.
2002). Eels from near Miami and Tampa, Florida, showed high similarities
to each other and to eels from China. Those from near Homestead,
Florida, grouped with eels from Malaysia, Vietnam, and Indonesia. Eels
from the population near Atlanta, Georgia, were distinct from other
North American animals and did not show a close relationship to any of
the Asian populations sampled. Although the potential for North Ameri-
can populations to interbreed is unknown, it appears likely that these eels
represent two or three biological species.
Other analyses that have led to recognition of cryptic species among
alien animals include studies of
Corbicula
clams in North America (Siri-
pattrawan et al. 2000), cladocerans in the Great Lakes (DeMelo and
Hebert 1994), and amphipods in central European waterways (Müller et
al. 2002).
Cryptic species have also been identified among other kinds of organ-
isms by DNA fingerprinting. Dogwood anthracnose, a fungal disease of
shrubs of the genus
Cornus
, first appeared on flowering dogwood (
C.
florida
) in eastern North America in 1976. It has since become a major
cause of dogwood mortality and has spread to the Pacific dogwood (
C. nut-
tallii
) in the western United States and Canada.The fungal agent associated
with the disease was found to be a member of the genus
Discula
and was
named
D. destructiva
. Subsequently, however, studies of
Discula
forms from
dogwoods have revealed a second, as yet unnamed, form of
Discula
.
Studies of these
Discula
fungi are complicated by the fact that their
reproductive stages have not been observed.The difficulties of identifying
and distinguishing fungi in their mycelial stages make molecular genetic
analysis advantageous. Trigiano et al. (1995) examined DNA fingerprints
of
Discula
cultures obtained from flowering dogwood and Pacific dog-
wood.These analyses showed that
destructiva
and the unnamed form were
quite distinct. They also showed that
destructiva
was nearly uniform in
genetic characteristics in the various populations sampled in eastern and
