Final Conclusions

Abstract

During the course of this book it must have become apparent that neither arthropods nor reptiles show particularly marked desert adaptations. Both groups include taxa whose ecophysiology is such that they can exist and even thrive under desert conditions, mainly by avoiding thermal extremes and by the refinement of a pre-existing ability to economize in water. Nevertheless, lizards of the Australian genus Egernia are unable to reduce evaporative water loss below a certain level; and the persistence of temperate-adapted taxa in the arid zone is possible only in refugia offering relief from aridity (Henzell 1982). Furthermore, selection for arid adaptation in Amphibolurus spp. has not resulted in marked changes in the mechanisms regulating exposure; but all species of the genus prolong exposure when subjected to high heat loads (Bradshaw and Main 1968), while the rates of water loss of arid zone species are lower than those of species from temperate regions (Bradshaw 1970). Again, arid-adapted species of Phrynosorna increase their periods of exposure by retreating to their refuges at higher body temperatures or heat loads than do temperate-adapted species (Heath 1965). Morphological adaptations are primarily modifications for burrowing in or running over sand, whilst no unique anti-predator devices have been evolved in the desert.