Biology Reference
In-Depth Information
A
B
y
=
-10.05
x
+
39.70
r
=
-0.81,
n
=
319
y
=
-8.54
x
+
33.88
r
=
-0.96,
n
=
11
6
4
2
0
3.4
3.6
3.8
3.4
3.6
3.8
C
D
y
=
-10.81
x
+
40.45
r
=
-0.98,
n
=
9
y
=
-10.25
x
+
38.90
r
=
-0.83,
n
=
274
6
4
2
0
3.4
3.6
3.8
3.4
3.6
3.8
Temperature
-1
(1000/K)
Figure 9.13. The prediction that direct temperature effects on speciation rates are
responsible for latitudinal gradients in species diversity was tested by Allen and
collaborators, who have shown that diversity can be predicted from the biochemical
kinetics of metabolism, as shown by the examples which illustrate the effects of mean
ambient temperatures on species richness of North American trees (A), Costa Rican
trees along a 2600m elevational gradient on Volcan Barva (B), North American
amphibians (C), and Ecuadorian amphibians along a 4000m elevational gradient in
the Andes (D). From Allen, Brown, and Gillooly (
2002
). Reprinted by permission of
the authors and the American Association for the Advancement of Science.
the tropics. They compared rDNA substitution rates for a group of
closely related plant species from different biomes in the western
Pacific. Rates were indeed higher in habitats with greater biologically
available energy. Martin and McKay (
2004
) compared the within-species
patterns of mitochondrial DNA variation across 60 vertebrate species
from two oceans, six continents, and 119 degrees latitude. After con-
trolling for geographic distance, they found greater genetic divergence
of populations within species at lower latitudes, providing further strong
support for the hypothesis. Kaspari et al.(
2004
) have shown that the
energy-speciation hypothesis is the best predictor of ant species richness,
i.e., it predicts the slope of the temperature diversity curve and accounts
for most of the variation in diversity.
