BIODIVERSITY AND CLIMATE 195
Table 9. Predicted palaeotemperature and palaeolatitude values for the Middle Eocene Messel Shale fauna,
Germany
Species
Reptiles
Ectotherms
Tetrapods
Genera
Reptiles
Ectotherms
Tetrapods
Families
Reptiles
Ectotherms
Tetrapods
Composition
39.7%
46.0%
n = 63
43.4%
50.9%
n = 53
40.0%
47.1%
n-34
MAT (°C)
16.2 ±3.6
13.6 ±3.8
7.5 ±5.4
17.9 ±3.5
16.5 ± 3.6
10.0 ± 5.5
20.0 ± 3.6
13.9 ±4.3
15.7 ±6.1
CMM (°C)
7.6 ± 5.7
4.4 ± 6.2
-2.8 ± 8.5
9.5 ± 5.6
8.1 ± 6.0
0.0 ± 8.7
12.5 ± 5.4
4.8 ± 6.5
6.1 ± 9.3
Absolute
latitude (deg.)
35.8 ± 5.6
40.4 ± 5.5
50.8 ± 6.0
32.9 ± 5.3
35.5 ± 5.0
46.2 ± 6.3
30.6 ± 6.8
40.5 ± 7.7
3.4 ± 8.5
See text for description of the method
Table 10. Palaeotemperature and latitude estimates for the Middle Eocene of Messel, based on other data (see
text for details)
Modern values
Fossil floras
Presence of fossil crocodilians
Presence of fossil palms
Palaeogeography
MAT (°C)
8.6
25-30
>14.2
>13
CMM (°C)
0
>10
>5.5
>0
Absolute latitude
(deg.)
49.8
44.0 ± 0.9
faunas changed, such that the assemblage of one
interglacial will be different from the next in the
same place, they still represent the same climate
interpretation (e.g. Elias 1994): different taxo-
nomic participants, but the same physiologically
dependent diversity structure.
Although the results of this study strongly
imply an underlying fundamental relationship
between environmental energy procurement
and terrestrial taxonomic diversity, the exact
mechanism by which this proceeds has not been
addressed. It is possible that it could be through
affecting evolutionary rates (i.e. generation,
mutation and selection) as postulated by various
authors (Stevens 1989; Currie 1991; Rohde
1992). Area is also important, and has been
shown to be a fundamental determinant of
global diversity patterns (MacArthur & Wilson
1963; Sepkoski 1976; Rosenzweig 1995), and it is
interesting to note that not only do areas of high
orographic relief fall off derived regressions
using the methodology in this study, but so too
do islands (Fig. 16).
These relationships between diversity and
energy procurement have some important
consequences. Firstly, if the relationship
between the proportion of ectotherms and
endotherms is a function of climate (Fig. 11)
then this may indeed provide a tool for palaeo-
climate as suggested by Ostrom (1970), and
supported by the experiment using the Messel
Fauna presented in his paper. However, at this
stage such an application should be viewed with
caution, since it is unclear why the proportion of
ectotherms to endotherms should follow the
strong linear trend observed in Figure 11.
Secondly, if energy, as temperature, is the
limiting factor for ectotherms, then as tempera-
tures increase towards low latitudes not only
should ecotherm diversity increase, but the
proportion of ectotherms comprising faunas
should also increase. This is indeed the case (Fig.
11), and this would seem to imply that the limit
on reptile diversity in the modern world is
contemporary climate, which has major impli-
cations for the consequences of future climate
