BIODIVERSITY AND CLIMATE 193Table 7. Spearman rank test rho values for environmental variables and the percentage of fauna that are
represented by herptile (amphibian + reptile) species, by region
n
Absolute latitude
Elevation
MAT
MART
CMM
WMM
Radiation
Cumulative T 0
Cumulative T 5
Annual precipitation
P range
Months T 10 P 40
PET
Mean annual NDVI
NDVI ISD
South
America_ - - - - - - - - - - - - - - -North
America144
-0.923
NS
0.902
-0.489
0.820
0.897
NS
0.913
0.918
0.520
0.333
0.799
0.901
0.816
-0.832Europe204
-0.861
NS
0.769
NS
0.602
0.792
0.830
0.772
0.807
NS
NS
0.380
0.781
0.588
-0.817Arabia_ - - - - - - - - - - - _ - - -Southern
Africa21
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NSAustralia40
NS
NS
NS
NS
NS
NS
NS
NS
NS
-0.731
NS
-0.763
NS
NS
NS(p < 0.0001; NS, not significant, p > 0.0001)consequences of barriers to dispersal during the
Cenozoic. Similarly, the diversity of most
organic groups follows distinct patterns of diver-
sification through time (Sepkoski 1996), which
means that the overall diversity of any group at
a specific moment will depend on where it is
placed in its diversification history.
These historical factors appear to affect the
taxonomic composition of the fauna (names),
rather than absolute numbers or the relationship
between species diversity and environmental
variables. The correspondence analysis of North
American and European non-avian tetrapod
generic names (Figs 13 and 14, Table 8),
supports this. Axis 1 (Fig. 14) reflects historical
compositional differences between the two
continents, but the remaining variance com-
prises the physiological structure of the diversity
(temperature, axis 2, and water, axis 3; Figs 13
and 14), which dominate when the continents
are considered individually. This is consistent
with studies of Pleistocene beetle assemblages
that provide a sensitive measure of palaeo-
climate throughout the Quaternary (Atkinson et
al 1986). Despite the fact that with each inter-
glacial-glacial fluctuation the composition of the
Fig. 13. The results of a correspondence analysis (CA) of North American and European genera, (a) Axes 1
and 2, which comprise 65.2% of the total variance, (b) Axes 3 and 4.