Response to environmental change: Genetic variation and fitness in Drosophila buzzatii following temperature stress

Abstract

How do organisms adapt to environmental change? This question is not new, and was the focal point of studies of natural animal populations by Andrewartha and Birch (1954), Levins (1968), Parsons (1983), and Hoffmann and Parsons (1991). For the conservation of rare species, how populations respond to environmental change is an important consideration when estimating the level of care and monitoring that should be expended to guarantee their survival. Few environments are truly constant, either in time or space, and therefore environmental change, at some scale, will affect the majority of animal and plant species (Grime, 1989). Many recent changes to the environment have been induced by humans over a much shorter time frame than normal without human disturbance (Dobson et al., 1989; Holt, 1990; Kareiva et al., 1983). Such changes may cause physiological stress that is expressed by a reduction in growth or performance. Where genetic variation is present for resistance to stress factors, populations may adapt according to the stress experienced. Without this variation, no genetic response is possible, although stress effects will continue to act on the physiology, influence population size, and may cause extinction. Therefore, knowledge of the effects of stress and of genetic variation for stress resistance is necessary for decision-making with respect to choices of reserves designed to protect particular species, choosing the individuals to introduce to a reserve, and estimating long-term performance of populations in environments that may change unpredictably.