Biology Reference
In-Depth Information
from most of central Europe during historic times. Also, it has recently been pro-
posed that
Rana lessonae
had at least one native historic population in Great Britain
(Gleed-Owen, 2000; Beebee et al., 2005; Snell et al., 2005; but see Langton and
Burton, 2006, for a contrary opinion) even though current populations derive from
introductions. Normally, such an instance would be excluded from Table A.1; how-
ever, the introduction is so well-known and documented (and the involved lineages
are genetically distinct) that I have elected to include it in the table for the sake of
completeness. Second, there is a number of species of questionable introduction
status in certain areas, as discussed in Chapter 3. For example, it is widely assumed
that most of the geckos and skinks to be found in the eastern reaches of the Pacific
(and parts of the Indian Ocean) were introduced by humans (e.g., Beckon, 1992;
Moritz et al., 1993; Austin, 1999). Similar claims are made for populations of
Iguana iguana
and
Geochelone carbonaria
in the Caribbean (e.g., Censky, 1988;
Corke, 1992) and are becoming rather commonplace for a variety of species on
Mediterranean islands (e.g., Böhme and Wiedl, 1994; Corti et al., 1999). As dis-
cussed earlier, many of these claims are reasonable on biogeographic, morphologi-
cal, or genetic grounds but are problematic because direct evidence in support of
these claims hasn't been provided in most instances and details delineating native
from introduced ranges are lacking for all examples. I am happy to assume that
many of these hypotheses will eventually be demonstrated to be correct; nonethe-
less, I have largely left such instances out of this database for two reasons: (1) the
quality of evidence in support of such claims is generally not yet very advanced,
and it becomes difficult to justify inclusion of these claims with the same level of
confidence that characterizes the other entries in this database, which are based on
discovering species unobserved during older surveys, or known with certainty to be
foreign, or whose introduction has been directly admitted/observed; and (2) delet-
ing claims of prehistoric introductions, even if they later prove true, has no practical
effect on the analytical goals of assessing the modern phenomenon of herpetologi-
cal homogenization. Exclusion of these relatively few examples is not intended as
a curt dismissal of the truth of these claims so much as a desire to await clearer evi-
dence before including them. For some island groups, where evidence of recent
introduction is clearer and explicitly presented, I have included these species as
introductions even though they may not be listed as such for nearby areas for which
compelling arguments have not yet been made.
3.
Success
. This cell records whether or not the introduction was reported to be
established at the time of the most recent literature citation for the population in
question. Categories are “yes” if established, “no” if not established, or “?” if the
status of the introduction could not clearly be inferred from the literature.
Populations that were successfully established for years but later became extinct
(e.g.,
Podarcis sicula
in Pennsylvania) are included in the database as failures.
Including data for both established and unsuccessful introductions was done to
assess relative success of introduction pathways and to better assess pathway
importance.
