Biology Reference
In-Depth Information
Fig. 3.1
Growth in number of scientific studies that treat the ecological and evolutionary impacts
of alien reptiles and amphibians
by the large number of literature claims not surveyed here that purport, but do not
document, the decline of native species of herpetofauna coincident with the advent
of alien forms.
The late genesis of these impact studies is problematic in another way. The
absence of such studies seems sometimes to have been interpreted as demonstrating
the absence of impacts, especially when combined with the absence of obvious
effects upon casual inspection - effects that we've grown to expect to be obvious
because they are apparent for many plant, mammal, insect, or forest-pathogen inva-
sions. The problem is that impacts caused by invasive herpetofauna are usually not
obvious, even to trained biologists. Instead, they have proven to be subtle and diffi-
cult to discern without careful study. This form of denial was perhaps most apparent
in the case of the brown treesnake - a species now widely viewed as the poster child
for invasive herpetofauna, but which was vehemently denied as having any role in
Guam's bird declines until years of careful research (Savidge, 1987a; Savidge et al.,
1992) demonstrated that position to be baseless. But earlier claims for the neutral
effect of Florida's alien herpetofauna (L.D. Wilson and Porras, 1983; Butterfield
et al., 1997) - claims repeated for other jurisdictions too (e.g., McKeown, 1996) -
also seem to reflect this pattern of reasoning. In raising this issue, I in no way intend
to argue that most herpetological introductions do or will impose damaging
impacts. I simply don't know whether that's true or not; insufficient data have been
gathered to allow for generalizations. But I will argue that the diversity of evidence
provided above shows herpetological invasions cause or are likely to cause far more
damage than they have hitherto been credited with. Moreover, I suggest this
