Present address: H. Dingle, School of Life Sciences, University of Queensland, Brisbane, Australia.
Altitudinal variation in behavioural thermoregulation: local adaptation vs. plasticity in California grasshoppers
Article first published online: 17 MAR 2005
Journal of Evolutionary Biology
Volume 18, Issue 4, pages 1087–1096, July 2005
How to Cite
SAMIETZ, J., SALSER, M. A. and DINGLE, H. (2005), Altitudinal variation in behavioural thermoregulation: local adaptation vs. plasticity in California grasshoppers. Journal of Evolutionary Biology, 18: 1087–1096. doi: 10.1111/j.1420-9101.2005.00893.x
- Issue published online: 11 MAY 2005
- Article first published online: 17 MAR 2005
- Received 25 August 2004; revised 9 December 2004; accepted 14 December 2004
- life history;
- local adaptation;
- thermoregulatory behaviour
We investigated the adaptive significance of behavioural thermoregulation in univoltine populations of the grasshopper Melanoplus sanguinipes along an altitudinal gradient in California using laboratory tests of animals raised under different temperatures. Trials consisted of continuous body temperature measurements with semi-implanted microprobes in a test arena, and observation and simultaneous recording of behavioural responses. These responses included mobility, basking and orientation of the body axes (aspect angle) towards a radiation source. Mobility and basking are determined by the altitudinal origin of the parental generation and not by the temperature treatments. With increasing altitude, individuals tend increasingly to raise body temperatures via mobility and increased basking. In contrast, body orientation towards the radiation source is influenced by the temperature treatments but not by the altitude of origin. Individuals experiencing higher temperatures during rearing show a lower tendency to lateral flanking. We conclude that body orientation responses are not adapted locally. In contrast other components of the behavioural syndrome that increase body temperature, such as mobility and basking, are adaptive in response to local selection pressure. The thermoregulatory syndrome of these grasshoppers is an important contribution to life-history adaptations that appropriately match season lengths.