Biology Reference
In-Depth Information
Chapter 3
Impacts of Alien Reptiles and Amphibians
The entire motivation for concerning ourselves with invasive alien species, of
course, relates to the ecological and economic damage these species cause. For
many non-herpetological taxa, as noted in Chapter 1, damages have been extensive
and severe, justifying the considerable attention that has been devoted to a host of
invasive pests of all groups. As for these better-known taxa, when determining the
degree of attention that alien reptiles and amphibians might merit as a management
problem it is imperative to assess to what extent these species inflict damage.
Clearly, if these animals are not affecting natural or human ecosystems, concern for
their introduction will be lessened. And, indeed, it has been argued that most reptile
and amphibian introductions to Florida provide no such impact, and the threat of
alien herpetofauna there has been largely discounted (L.D. Wilson and Porras,
1983; Butterfield et al., 1997). Alternatively, if it be shown that alien reptiles and
amphibians do cause an array of ecological or societal damages, a greater responsi-
bility for management response would inhere. In either event, a broader awareness
of these impacts or their absence would improve our assessment of the relative
standing of alien reptiles and amphibians as environmental, conservation, or social
problems. It would concomitantly serve to identify obvious research needs for fur-
ther clarifying extent and ecological mechanisms of impact as well as control and
mitigation measures.
A broad survey of ecological impacts attending invasive reptile and amphibian
introductions has not previously been available. In providing one here, I confine my
attention to studies that clearly demonstrate some level of impact from alien her-
petofauna and that provide some evidence or compelling argument as to what the
mechanism of such impact might be. In including instances that provide only reasoned
argument to identify impact mechanism I hope to highlight several hypotheses that
have languished in the literature for lack of further investigation. The literature
occasionally contains correlational evidence that simply notes the decline or disap-
pearance of a native species to be coincidental with expansion of a naturalized alien
(e.g., Münch, 2001). However, such correlations need not result from the intro-
duced alien per se; both species may simply be responding differently to underlying
environmental changes (cf. L.D. Wilson and Porras, 1983 for herpetological
examples). Such instances are generally omitted in this summary because evi-
dence identifying the causative mechanism of replacement is not provided.
