ABSTRACT
Evolutionary responses to pollution are referred to as resistance. It is implicit that resistance has a genetic basis, and what is known of its genetic inheritance is outlined in section 13.5. This chapter considers how genetic changes in resistance come about. Resistance represents an evolutionary response to environmental changes resulting from pollution, and the first sections of this chapter describe the general phenomenon of evolutionary response to environmental change. Pollution represents an environmental change for the worse, and resistance generally defends organisms against the deleterious consequences of pollution. Such defence may reduce an organism’s mortality rate, but this is sometimes expensive, using energy and/or nutrients that could otherwise have been used for reproduction or somatic growth. Defence may, therefore, involve a tradeoff between production and survival: increased survival may only be obtained at a cost of reduced growth or reproduction. As a result, resistance may have a fitness cost in an unpolluted environment. The possible physiological basis of this trade-off has been consid-
ered in Chapter 8, the evolutionary implications are considered here in section 13.3. Four cases studies of evolutionary responses to pollution at the end of the chapter consider the evolution of pesticide resistance, of heavy metal tolerance in plants, of industrial melanism and of TBT resistance in dog whelks. These include some of the best documented studies of evolutionary responses to environmental changes. They show that the evolution of resistance generally consists in the selection of pre-existing genes rather than the appearance of new genes. The first sections of this chapter are quite theoretical, and an attractive approach for those encountering this material for the first time may be to begin by reading the case studies.
