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Evolution in Constant and Fluctuating Environments: Thermal Tolerances of Desert Pupfish (Cyprinodon)

James H. Brown and C. Robert Feldmeth
Evolution
Vol. 25, No. 2 (Jun., 1971), pp. 390-398
DOI: 10.2307/2406931
Stable URL: http://www.jstor.org/stable/2406931
Page Count: 9
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Evolution in Constant and Fluctuating Environments: Thermal Tolerances of Desert Pupfish (Cyprinodon)
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Abstract

We compared the thermal tolerances and ability to acclimate to environmental temperature of populations of desert pupfish from thermally constant springs and thermally fluctuating streams and marshes. All populations had similar abilities to withstand extreme temperatures and to acclimate. Even Cyprinodon diabolis, which has been isolated in a thermally constant spring for at least 30,000 years and undergone many morphological changes, is capable of tolerating as wide a range of temperatures as C. salinus and populations of C. nevadensis which encounter temperature fluctuations from 0 to 40 C in their present habitats. These results suggest that some homeostatic systems may be highly resistant to evolutionary change and that the usually predicted correspondence between the range of an environmental parameter which an organism encounters and the range of that parameter which it can tolerate does not always occur.

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