Biology Reference
In-Depth Information
management. I find it useful to organize the most relevant research issues along the
lines adopted by Rejmánek et al. (2005) for plant invasions. Rejmánek and com-
pany asserted that five research questions comprise the core of invasion biology and
that these questions need to be answered if we are to progress in understanding and
controlling invasions. The questions are:
1. Which taxa invade?
2. How fast?
3. What makes ecosystems invasible?
4. What is the impact?
5. How can we control or eradicate harmful invaders?
Let us address for each what research could most profitably be undertaken in the
near term to advance understanding and management of herpetofaunal invasions.
Which Taxa Invade?
As noted earlier, knowledge of which factors lead to establishment or invasion suc-
cess is virtually undeveloped for alien reptiles and amphibians except for the study
by Bomford et al. (2005, in press). But a variety of ecological attributes - especially
biotic attributes - remains unexamined. Meshaka (2004) noted that most of Florida's
established herpetofauna shared a small suite of attributes linked to early and pro-
longed breeding, broad diet, and tolerance of human disturbance. More broadly,
Rodda and Tyrrell (in press) compared ecological features hypothesized to charac-
terize reptiles and amphibians among the three assemblages of urban, pet-trade, and
invasive herpetofauna. They found that features hypothesized to favor invasiveness
overlapped considerably with those features thought to favor persistence in urban
settings and, to a lesser extent, with those that favor selection for the pet trade. This
work presents a useful summary of hypotheses that might explain herpetological
invasiveness, but statistical tests demonstrating a preponderance of these attributes
among naturalized aliens compared to other herpetofauna remain to be done. Such
studies are currently hindered by lack of broad summaries of the required ecological
information, as well as by the lack of a reasonable means of ranking herpetological
invasiveness. Even though a few herpetofaunal species can clearly be pointed to as
demonstrably invasive, and others are just as demonstrably not invasive, develop-
ment of a reliable metric of herpetological invasiveness has yet to be attempted.
Indeed, opinions differ as to whether invasiveness should be defined based on eco-
logical impacts or on magnitude and rapidity of range expansion (e.g., Richardson
et al., 2000a; Daehler, 2001), although the two likely have a high degree of overlap.
Regardless of what definition might be chosen, we currently lack objective criteria
for classifying degree of invasiveness among alien herpetofauna. This clearly
imposes an unmet precondition for identifying which species invade. Beyond that
remains the large body of work to be undertaken in determining whether herpeto-
logical invasiveness can be predicted on the basis of species attributes.
