Biology Reference
In-Depth Information
pathways - the pet trade and “intentional” pathways - are intimately related and
form a nexus of aesthetic motivation. Included in this too are the minor pathways
of exhibit and zoo releases. These four pathways combine to form the primary
means by which alien herpetofauna have been moved and naturalized in the past
several decades (Fig. 2.36). They clearly represent a deliberate failure of social
responsibility among the citizenry of many countries. The major pathways of
cargo stowaways and nursery trade - as well as the minor pathways of aquacul-
ture contamination and vehicle stowaways - also represent a single general
nexus representing unintentional transport as a direct consequence of increasing
international trade volume. These do not constitute a failure of personal respon-
sibility so much as a failure to recognize a statistically predictable phenomenon
and programmatically respond to it. This is the second major axis of modern
introductions (Fig. 2.36). Between these axes of aesthetic motivation and con-
taminated trade goods the majority of modern herpetofaunal introductions are
accounted for. The deliberate pathways involving introduction for biocontrol or
for food use have become minor in the second half of the 20th century (Fig. 2.15),
although the latter is still an important means of introducing the problematic
bullfrog (
Rana catesbeiana
) to many developing counties. Given the ecological
impacts that this species likely inflicts (see following chapter), its introduction
alone merits the effort to close the food pathway, even though overall magnitude
of that pathway is now small.
Despite the fact that the generalizations discussed here have been focused on major
introduction pathways, it must be borne in mind that the minor pathways cannot be
Fig. 2.36
Cumulative growth in importance of deliberate aesthetic motivations leading to herpe-
tological introductions (blue) vs. unintentional introductions resulting from trade activities (red)
