Biology Reference
In-Depth Information
Figure 9.12. Effect of incubation temperature on mass-corrected embryonic
development time for aquatic ectotherms (fish, amphibians, zooplankton, aquatic
insects) and birds. Reprinted from Gillooly, Charnov, West, Savage, Van, and
Brown (
2002
), with the permission of MacMillan Publishing Ltd., and the authors.
with that of vertebrates at another, i.e., comparisons should not be made
across phyla, but should be restricted to lower taxa.
We conclude that, although evidence is still limited, the important
study of Gillooly et al.(
2002
), in particular, demonstrates that generally an
increase in temperature does indeed shorten generation times, supporting
one key element in the hypothesis that effective evolutionary time
determines latitudinal gradients in diversity.
Early studies of the effect of temperature on mutation rates were
discussed by Rohde (
1992
, references therein). There is indeed evidence
that raised temperature increases mutation rates (e.g., Timof´eff-
Ressovsky et al.
1935
; Bazin et al.
1997
), but more studies are needed to
provide evidence for more taxa and a variety of genes.
There is a wealth of evidence showing an acceleration of physiolo-
gical processes with temperature. Pandian and Vivekanandan (
1985
)
have shown that maintenance metabolism, food intake, and growth
arehigherintropicalthanincold-waterfish,andaccordingtoTarr
(
1969
), high temperatures lead to a decrease in metabolic loss and an
increase in food consumption of fish. Although most selection is char-
acterized by stasis, and although mutations and selection do not deter-
mine speed of speciation on their own, but in conjunction with
mechanisms that bring about genetic isolation, it seems intuitively likely
that, under otherwise identical conditions, species that have higher
mutation rates, faster physiological processes, and shorter generation
