Biology Reference
In-Depth Information
What Is the Impact?
This is one area for which some research progress has been made with alien reptiles
and amphibians, as detailed in Chapter 3. Nonetheless, as frequently noted throughout
this topic, research has been decidedly biased toward a handful of species, and investi-
gation into a taxonomically broader sample of naturalized species would be highly
desirable. Although a diversity of impacts is already documented for alien herpeto-
fauna, many categories of impact can point to only one or two exemplars. Partly, this
reflects the difficulty of collecting ecological impact data for many of these species.
This is especially true for demonstrating predation impacts, which are often extremely
time sensitive and difficult to detect or demonstrate once native prey are decimated.
Yet, it seems likely that the high densities achieved by many alien reptiles and amphibians
will make direct effects on prey species and secondary effects on ecosystems more
widespread than currently appreciated. Similarly, investigations into health impacts
and economic impacts of invasive herpetofauna have just begun, and additional dam-
ages are likely to be identified. In short, despite the fact that research on impacts has
grown considerably since the 1980s, studies are not yet sufficiently dense to allow us
to assess how frequently naturalized herpetofauna are likely to prove damaging. There
is likely to be continued political resistance to responding effectively to herpetological
invasions until such a rough estimate can be provided, even though the growing
number of herpetological “train wrecks” is garnering some increased political atten-
tion. Because waiting for continued train wrecks is a poor management paradigm, bet-
ter scientific understanding of the likely pool and frequency of impacts attendant upon
herpetofaunal invasions is critical for better allocation of management efforts.
Additionally, we need to identify the native ranges of a variety of species widely
dispersed by humans. This is critical for clarifying the validity and conservation
status of some species, the geographic origins of other species, and the native com-
position of some insular herpetofaunas (c.f., Chapter 3). Such research has already
proven important for conservation purposes in some instances (e.g., Iverson et al.,
2001), and further instances await elucidation (c.f., Chapter 3, Appendix B). The
considered application of sensitive molecular techniques is likely to be most useful
for this purpose, but has rarely been applied to these questions in a comprehensive
fashion. Until such research becomes more widely undertaken, many instances of
presumptive human introduction (Appendix B) will remain speculative. That these
speculations are sometimes in error (e.g., Iverson et al., 2001) and can have practi-
cal conservation consequences (e.g., Austin et al., 2003; Palkovacs et al., 2003)
highlights the importance of this research need beyond its obvious application to
basic evolutionary and biogeographical understanding.
How Can We Control or Eradicate Harmful Invaders?
As I've noted repeatedly, control involves prevention, eradication, and population
reduction/control, each operating at a different stage of the invasion process. The first
