Biology Reference
In-Depth Information
Fig. 2.22
Cumulative growth in reptile and amphibian introductions for the five geographic
regions receiving the greatest numbers of introductions. Asia = red, Caribbean = pink, Europe =
yellow, North America = blue, and Pacific Islands = green
Table 2.5
Exponential growth rates for regions receiving the greatest numbers of
introductions
Pathway
Time span
Growth equation
R
2
Doubling time (years)
Asia
1880-1999
y = 0.4470e
0.4114x
0.9696
16.8
Caribbean
1850-1999
y = 3.1657e
0.2179x
0.9875
31.7
Europe
1850-1999
y = 11.326e
0.2287x
0.9815
30.2
North America
1850-1999
y = 1.6030e
04133x
0.9821
16.7
Pacific
1850-1999
y = 7.7378e
0.2089x
0.9873
33.0
This same cause is suggested by the higher success rates reported on Mediterranean
and Atlantic islands relative to mainland Europe. Both of these insular areas receive
adequate or considerable herpetological scrutiny and are unlikely to have unsuccess-
ful establishments heavily under-reported. Differences with mainland Europe likely
reflect the more equable climate of the insular areas.
Cumulative growth curves for the five geographic regions receiving the greatest
numbers of introductions indicate that each has experienced exponential growth in
introduction rates (Fig. 2.22), although Asia has only done so since the 1880s, when
the first introductions were documented. Growth rates throughout this 150-year
period have been highest for North America, consonant with its high overall num-
bers of introductions (Fig. 2.20), and for Asia, which trails behind North America
in total numbers of introductions (Fig. 2.20) because of its later onset of introduc-
tions. Data for Europe suggest a lower growth rate (Table 2.5), but this could partly
result from poorer data quality: dates for most European introductions available to
me are less well documented in the literature than for North America (dates availa-
ble for 24% of my European records vs. 51% of those from North America).
