Biology Reference
In-Depth Information
reptiles and amphibians to transport new parasites to naive herpetofaunas, but
whether this potential has translated into damage to native herpetofaunas is totally
uninvestigated.
Observations of epidemic mortality events caused by viral or mycoplasma
agents in
Actinemys marmorata
in California and Washington states, United States,
were noted to have occurred in populations into which alien species of turtles had
previously been introduced (Holland, 1994). This led to the reasonable hypothesis
that the alien turtles served as vectors of a new disease agent into these populations.
This speculation could not be directly tested but was consistent with the frequent
maintenance of pet-store turtles under crowded and unsanitary conditions, which
could easily allow for rapid acquisition of novel disease agents prior to a turtle
escaping or being released (Holland, 1994).
Under somewhat more controlled circumstances, a total of 29 species of alien
ticks has been imported into the United States on captive reptiles (Burridge and
Simons, 2003), and at least seven of these have established breeding populations at
captive reptile facilities (S.A. Allan et al., 1998; Burridge et al., 2000a; Simmons
and Burridge, 2000, 2002). One alien tick,
Amblyomma rotundatum
, has been
found on feral
Bufo marinus
in Florida, which is presumed to have served as the
vector to that new locale (Oliver et al., 1993). That tick has a broad host range in
its native Central and South America but has not yet been reported from native
wildlife in Florida. Another species,
A. dissimile
is also established in Florida, is
thought to have arrived on imported reptiles, and has been found infecting native
reptiles (Bequaert, 1932). It continues to arrive on imported reptiles from Central
and South America (Burridge and Simons, 2003). Several of these alien ticks are
readily capable of switching onto hosts to which they have no prior history of expo-
sure (Burridge, 2001), suggesting a capability to infect native reptile species. The
potential for this wide array of ticks to vector diseases to native reptile and amphibian
populations has been largely uninvestigated, but two of these tick species can vector
reptilian haemogregarines, and severe infestations of one species have led to respi-
ratory distress and death in some reptiles (Burridge, 2001). The finding of lethal
infections of the tick-vectored
Ehrlichia ruminantium
or a close relative in a phylo-
genetically varied array of captive snakes suggests that risks to native reptiles are
potentially serious (Kiel et al., 2006); however, this potential remains unexamined
in wild populations.
Community Homogenization
Little attention has yet been paid to the broader-scale effects that accumulating
introductions have for homogenization of herpetological communities. One excep-
tion is a recent investigation into regional changes in herpetological communities
attending alien introductions to Florida. This study found that introductions made
to date have increased homogenization of communities at the small spatial scale of
adjacent counties but had not yet shown a similar tendency toward homogenization
