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Conservation of Mass‐Specific Metabolic Rate among High‐ and Low‐Elevation Populations of the Acridid Grasshopper Xanthippus corallipes

Patricia Daly Ashby
Physiological Zoology
Vol. 70, No. 6 (November/December 1997), pp. 701-711
DOI: 10.1086/515877
Stable URL: http://www.jstor.org/stable/10.1086/515877
Page Count: 11
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Conservation of Mass‐Specific Metabolic Rate among High‐ and Low‐Elevation Populations of the Acridid Grasshopper Xanthippus corallipes
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Abstract

ABSTRACT High‐elevation populations of many grasshopper species produce small adults in response to shortened growing seasons and cooler ambient temperatures. Mass‐specific metabolic rate tends to increase with elevation, and several authors have argued that this is an adaptation to accelerate development. In the present study, the relationship of thermoregulation and metabolism was investigated in adults of the acridid grasshopper Xanthippus corallipes from six populations along an elevation gradient. Thermoregulation was measured in the field, and several lines of evidence suggested that afternoon body temperatures were actively maintained within each population. Populations were found to maintain stable afternoon body temperatures that correlate negatively with elevation. Elevation had a strong negative effect on adult mass. Mass‐specific metabolic rates at 35° and 45°C correlated positively with elevation. However, population differences in mass explained most of the variation in mass‐specific metabolic rates, and when mass was used as a covariate, the effect of elevation disappeared. Mass‐specific metabolic rates at afternoon field body temperatures were estimated and found not to differ among populations. Thus, differences in thermoregulation offset the effect of mass on mass‐specific metabolic rate across populations, such that X. corallipes adults exhibited a common mass‐specific metabolic rate in the wild, independent of large population differences in mass and ambient temperatures.

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