Biology Reference
In-Depth Information
Contributions of the different taxa to each pathway vary in importance and are
generally strikingly different. Indeed, there is a distinctive taxonomic signature for
each pathway (Fig. 2.12). Biocontrol efforts involving reptiles and amphibians
have focused almost exclusively on frogs. Transportation via the cargo pathway
has been virtually restricted to frogs, lizards, and snakes. This is unsurprising
inasmuch as these taxa have many species that are small in size and with broad
physiological tolerance. Conversely, one could scarcely imagine turtles or crocodilians
accidentally hitch-hiking in cargo because their large sizes would make them
conspicuous. Similarly, most salamanders would be physiologically susceptible to
the dry and hot conditions that frequently accompany cargo transportation. The few
instances of their transport in cargo involve shipments of logs or tropical produce.
I know of other, unreported instances of salamander transport in christmas tree
shipments as well. Transport via the nursery pathway is similarly restricted and for
the same reasons. However, frogs form a higher percentage of introductions via the
nursery pathway, probably a reflection of the more conducive physiological condi-
tions presented by nursery materials for desication-prone amphibians. The food
pathway has also had restricted taxonomic representation, being dominated by
frogs (mainly
Rana
) and turtles (mainly
Pelodiscus
), although lizards have also
been involved. The only pathways that involve all taxa are, unsurprisingly, the pet
trade and its close aesthetic cognate, “intentional” introductions. Clearly, this
reflects the fact that humans who like and keep reptiles and amphibians are drawn
to a wide diversity of taxa and, hence, all groups are subject to some amount of
release or escape. Interestingly, taxonomic representation between those two
related pathways differs rather dramatically for turtles. This may reflect that the
large combined mass required to intentionally start a new population presents
“
”
Fig. 2.12
Frequency of taxonomic representation for each major pathway of herpetofaunal intro-
duction. Frogs = dark blue, salamanders = green, lizards = yellow, snakes = blue, turtles = pink,
and crocodilians = red
