Spatial extent of the data

Many of the macrophysiological patterns we have explored and sought to understand from a mechanistic perspective have required data covering a range of latitudinal bands. This raises the important question of how geographically extensive are the data available for this purpose (Chown et al. 2002a).

Perhaps unsurprisingly, the majority of the work on insect physiological ecology appears to have been undertaken in the Holarctic (Fig. 7.3). This clearly has to do with both the geographic distribution of scientists in the field and the restrictions of the investigation undertaken by

Figure 7.3 Global geographic extent of investigations of metabolic rate, water loss, development rate, upper lethal temperature, lower lethal temperature, and body temperature regulation in insects.

Source: Reprinted from Comparative Biochemistry and Physiology B, 131, Chown et al., 587-602, © 2002, with permission from Elsevier.

Chown et al. (2002a) (e.g. the non-Anglophone literature, especially from Asia, was largely excluded). Nonetheless, spatial variation in investigations of tolerances, metabolism, development and thermoregulation highlights several fascinating trends. Foremost among these is the tendency for investigations of particular traits to be biased to certain geographic regions. Thus, studies of lower lethal temperatures (LLTs) of insects tend to be undertaken in cold regions, and those of upper lethal temperatures in warm, often arid regions (Addo-Bediako et al. 2000). Similarly, investigations of desiccation resistance tend to be most common in desert regions (Addo-Bediako et al. 2001), and investigations of development rates in tropical species tend to be scarce (Honek 1996). These tendencies preclude firm conclusions regarding a range of issues, such as hemispheric variation in responses (Section 7.4), latitudinal variation in development rate, and covariation in environmental temperature and insect responses (Section 7.3) (Chown et al. 2002a). Clearly, if these questions are to be addressed in the future, then a carefully considered expansion of the geographic extent of insect macrophysiology will have to be undertaken.

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