Adaptive capabilities and fitness consequences associated with pollution exposure in fish

Abstract

Many fish populations are exposed to harmful levels of chemical pollution and selection pressures associated with these exposures have led to the evolution of tolerance. Our understanding of the physiological basis for these adaptations is limited, but they are likely to include processes involved with the absorption, distribution, metabolism and/or excretion of the target chemical. Other potential adaptive mechanisms include enhancements in antioxidant responses, an increased capacity for DNA and/or tissue repair and alterations to the life cycle of fish that enable earlier reproduction. Analysis of single-nucleotide polymorphism frequencies has shown that tolerance to hydrocarbon pollutants in both marine and estuarine fish species involves alteration in the expression of the xenobiotic metabolism enzyme CYP1A. In this review, we present novel data showing also that variants of the CYP1A gene have been under selection in guppies living in Trinidadian rivers heavily polluted with crude oil. Potential costs associated with these adaptations could reduce fitness in unpolluted water conditions. Integrating knowledge of local adaptation to pollution is an important future consideration in conservation practices such as for successful restocking, and improving connectivity within river systems.This article is part of the themed issue 'Human influences on evolution, and the ecological and societal consequences'.

Keywords: adaptation; chemical pollution; fish; genetic adaptation; single-nucleotide polymorphism; tolerance.

Figure 1.

Distribution of alleles for a DNA microsatellite within the CYP1A gene for guppies living in four rivers in Trinidad. The Vance and Morne rivers are unconnected by freshwater and have stretches that are heavily contaminated with crude oil, described in [27]. Within each polluted river, data are pooled for populations from unpolluted and polluted stretches as no frequency differences were observed. Numbers within the pie charts are the sizes (bp) of each allele.