Exploring links between physiology and ecology at macro-scales: the role of respiratory metabolism in insects

Sl. Chown et Kj. Gaston, Exploring links between physiology and ecology at macro-scales: the role of respiratory metabolism in insects, BIOL REV, 74(1), 1999, pp. 87-120
Citations number
Categorie Soggetti
Biology,"Experimental Biology
Journal title
ISSN journal
1464-7931 → ACNP
Year of publication
87 - 120
SICI code
The relationships between macro-ecological patterns and physiological inves tigations in insects, especially those dealing with respiratory metabolism, are assessed in an attempt to encourage the development of the interaction between macroecology and physiological ecology. First, we demonstrate that although physiological ecology has been explicitly concerned with a number of issues relating to species boundaries, many questions remain unanswered . We argue that there are essentially two ways in which the relationship be tween physiological tolerances and species range boundaries have been inves tigated. The correlational approach involves physiological inference, physi ological prediction, isocline analyses and climatic matching, and has often been criticized for a lack of rigour, while the experimental approach seek s to examine experimentally the relationships between physiological variabl es and range edges. Second, we use the recent debate on processes underlyin g latitudinal patterns in body size to caution against the conflation of pa tterns and processes operating at intraspecific and interspecific levels, t he dangers inherent in invoking single explanatory variables, and an undue focus on adaptationist (e.g. optimization) rather than nonadaptationist exp lanations or some combination of the two. We show that both positive and ne gative relationships between body size and latitude have been found at the intraspecific level and suggest that interactions between temperature-induc ed heterochrony, and the relationship between habitat durational stability, growing season length, and generation time can be used to explain these di fferences. Similar variation in documented patterns is demonstrated at the interspecific level, and the mechanisms usually proffered to explain such d ines (especially the starvation/desiccation-resistance hypothesis) are disc ussed. Interactions between various environmental factors, such as host-pla nt quality, and their effects on size dines are also discussed. Third, we a rgue that respiratory metabolism, as a measure of ATP cost, and its spatiot emporal variation are critical to many explanations of macroecological patt erns. Adaptive changes in metabolism reputedly involve both depression (str ess resistance) and elevation of metabolic rate, although recent studies ar e increasingly calling these ideas into question. In particular, flow-throu gh respirometry is revolutionizing results by allowing careful separation o f resting (or standard) and active metabolic rates. These techniques have r arely been applied to studies of metabolic cold adaptation in insects, one of the most polemical adaptations ascribed to high-latitude and high-altitu de species. We conclude by arguing that physiological investigations of spe cies tolerances are important in the context of macroecology, especially sp ecies distributional patterns and the possible impact of climate change the reon. However, we caution that relationships between abiotic variables, spe cies tolerances, and distributional ranges may be non-linear and subject to considerable modification by the presence of other species, and that many of the pressing questions posed by macroecology have not been addressed by insect physiologists. Nonetheless, we suggest that because an understanding of the dynamics of species distributions is of considerable importance, es pecially in the context of current conservation problems, insect physiologi cal ecology has much future scope.