Convergence and divergence in gene expression among natural populations exposed to pollution

We used Fundulus cDNA arrays to compare metabolic gene expression patterns in the brains of individuals among nine populations: three independent, polluted Superfund populations and two genetically similar, reference populations for each Superfund population. We found that up to 17% of metabolic genes have evolved adaptive changes in gene expression in these Superfund populations. Among these genes, two (1.2%) show a conserved response among three polluted populations, suggesting common, independently evolved mechanisms for adaptation to environmental pollution in these natural populations.Significant differences among individuals between polluted and reference populations, statistical analyses indicating shared adaptive changes among the Superfund populations, and lack of reduction in gene expression variation suggest that common mechanisms of adaptive resistance to anthropogenic pollutants have evolved independently in multiple Fundulus populations. Among three independent, Superfund populations, two genes have a common response indicating that high selective pressures may favor specific responses.Many natural populations are continuously exposed to chemical stressors. One indication of this is that in 2004, over 4.24 billion pounds of industrial chemicals were disposed or released to the environment by facilities required to report to the EPA, including 576 million pounds of air emissions and 210 million pounds of surface water releases [1]. What are the biological consequences of chronic exposure to environmental pollution? We addressed this question using natural populations of the teleost Fundulus heteroclitus that inhabit and have adapted to highly polluted Superfund sites [2-5]. These populations are exposed to some of the highest concentrations of aromatic hydrocarbon pollutants of any vertebrate species [6]. Compelling evidence for adaptation in these populations is that embryos from the polluted sites are resistant to the toxic effects of the contaminated