Abstract
BackgroundAnthropogenic disturbances can lead to intense selection pressures on traits and very rapid evolutionary changes. Evolutionary responses to environmental changes, in turn, reflect changes in the genetic structure of the traits, accompanied by a reduction of evolutionary potential of the populations under selection. Assessing the effects of pollutants on the evolutionary responses and on the genetic structure of populations is thus important to understanding the mechanisms that entail specialization to novel environmental conditions or resistance to novel stressors.ResultsUsing an experimental evolution approach we exposed Caenorhabditis elegans populations to uranium, salt and alternating uranium-salt environments over 22 generations. We analyzed the changes in the average values of life history traits and the consequences at the demographic level in these populations. We also estimated the phenotypic and genetic (co)variance structure of these traits at different generations. Compared to populations in salt, populations in uranium showed a reduction of the stability of their trait structure and a higher capacity to respond by acclimation. However, the evolutionary responses of traits were generally lower for uranium compared to salt treatment; and the evolutionary responses to the alternating uranium–salt environment were between those of constant environments. Consequently, at the end of the experiment, the population rate of increase was higher in uranium than in salt and intermediate in the alternating environment.ConclusionsOur multigenerational experiment confirmed that rapid adaptation to different polluted environments may involve different evolutionary responses resulting in demographic consequences. These changes are partly explained by the effects of the pollutants on the genetic (co)variance structure of traits and the capacity of acclimation to novel conditions. Finally, our results in the alternating environment may confirm the selection of a generalist type in this environment.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-014-0252-6) contains supplementary material, which is available to authorized users.
Highlights
Anthropogenic disturbances can lead to intense selection pressures on traits and very rapid evolutionary changes
For traits measured in hermaphrodites, the model with the lowest deviance information criterion (DIC) included an interaction between treatment and generation, and covariance between traits (Table 1)
As shown by the 95% highest posterior density interval (HPDI) [see Additional file 2], traits did not change across generations in the control treatment, except for a slight reduction in late fertility (Figure 1)
Summary
Anthropogenic disturbances can lead to intense selection pressures on traits and very rapid evolutionary changes. Evolutionary responses to environmental changes, in turn, reflect changes in the genetic structure of the traits, accompanied by a reduction of evolutionary potential of the populations under selection. Assessing the effects of pollutants on the evolutionary responses and on the genetic structure of populations is important to understanding the mechanisms that entail specialization to novel environmental conditions or resistance to novel stressors. It is important to consider the multivariate feature of traits in an organism to provide more robust predictions of the evolutionary trajectory of populations as a result of novel selection pressures [11]. The evolutionary potential of traits is constrained by the magnitude and sign of the genetic associations among the traits [12]. Several studies have shown that they can be altered (e.g. [15,18,19]), including by quick changes in environmental conditions [20,21]
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