Biology Reference
In-Depth Information
Green iguanas ( Iguana iguana ) have become abundant on Puerto Rico, where
they now pose an airstrike hazard at San Juan's international airport (Engeman et al.,
2005b). There have been five collisions of airplanes with iguanas at this location,
and flight operations were temporarily halted six times during a two-month period
in 2001 because of iguana incursions on the runways (Engeman et al., 2005b). The
size and abundance of these lizards make them an important airstrike hazard in San
Juan and of potential importance at airports in other parts of their introduced range
(Engeman et al., 2005b).
Scientific Loss
The irreversible damage that alien invasions can cause is not limited to ecological
and economic impacts but includes epistemological loss as well. Information lost
can include knowledge of original range for a species, evolutionary status of popu-
lations, and ecological relationships within invaded regions. Such knowledge loss
can have practical importance for conservation efforts.
Rampant introduction of reptile and amphibian species has resulted in many
species being cryptogenic; that is, the distinction between their native vs. introduced
ranges is obscure or totally unknown (Carlton, 1996). The term was originally
coined in the context of marine species, many of which have presumably hitch-
hiked on the bottoms of ships for thousands of years, resulting in complete uncer-
tainty about the extent of their original ranges. However, among reptiles and
amphibians many examples exist too, and most are derived from introductions
made prior to the historically recent period of scientific documentation. It is almost
certain that the set of lizards ( Gehyra mutilata , G. oceanica , Hemidactylus garnotii ,
Hemiphyllodactylus typus , Lepidodactylus lugubris , Nactus pelagicus ,
Cryptoblepharus poecilopleurus , Emoia cyanura , E. impar , Lipinia noctua ) that
occurs throughout most of the Pacific islands has been introduced by humans
through at least part of this region during the past two millennia. However, we do
not yet know in most cases exactly where they were introduced; we know in none
of these cases where exactly their native ranges lie. To discriminate among the two,
detailed molecular studies using a variety of sensitive markers and comprehensive
geographical sampling need to be done; to date, these are lacking. So, it remains
virtually certain that much of the currently occupied ranges of these species are due
to human introductions (e.g., Moritz, 1987; Beckon, 1992; Moritiz et al., 1993;
Fisher, 1997; Austin, 1999; Ineich, 1999), but details are opaque.
Identical problems hold in many other regions. In the Caribbean, which islands
were occupied by Eleutherodactylus johnstonei , E. martinicensis , Geochelone
carbonaria , and Iguana iguana prior to human activities are variously argued about
but not known with confidence (Underwood, 1962; Lazell, 1973; Lescure, 1983;
Censky, 1988; Corke, 1992; H. Kaiser, 1992, 1997; Breuil, 2002; Powell, 2004). It is
uncertain whether the population of Trachemys decussata on Grand Cayman is
native or introduced by Amerindians (Seidel, 1996). In France, the native range of
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