How does rising atmospheric CO2 affect marine organisms?

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Evolution to the Rescue
Bell, G. and Gonzalez, A. 2009. Evolutionary rescue can prevent extinction following environmental change. Ecology Letters 12: 942-948.

According to theory, whether evolution can save species from going extinct, due to the negative effects of rapid environmental change (such as unprecedented increases in the atmosphere's CO2 concentration and temperature), depends, in the words of the authors, "upon several crucial variables: population size, the supply of genetic variation, and the degree of maladaptation to the new environment." Edging towards a positive answer to this important question, they reference the widely demonstrated fact that "microbial populations often adapt rapidly to highly stressful environments, the classic example being antibiotic resistance in pathogenic bacteria (Levin et al., 1997)," and they go on to note that "animals and plants may also adapt rapidly to anthropogenic stress, including heavy metal pollution (McNeilly and Bradshaw, 1968), smoke damage (Kettlewell, 1973), herbicides (Jasieniuk et al., 1996), pesticides (Georghiou, 1972) and over-fishing (Handford et al., 1977)."

What was done
"Using techniques in experimental evolution," Bell and Gonzalez say they "tested the conditions for evolutionary rescue (ER)" in a study of hundreds of yeast populations that "were exposed to normally lethal concentrations of salt in conditions where the frequency of rescue mutations was estimated and population size was manipulated."

What was learned
The two researchers report that "in a striking match with theory," they observed "a clear example of the U-shaped curve hypothesized by Gomulkiewicz and Holt (1995) to characterize ER: the dual process of collapse under stress followed by selection leading to renewed adaptation and subsequent growth," which chain of events suggests that the original yeast population "contained a small number of resistant cells at the outset which were able to proliferate as the majority of susceptible cells were dying."

What it means
The Canadian scientists say their results "demonstrate that rapid evolution is an important component of the response of small populations to environmental change," and that they "provide the first experimental demonstration of ER and confirm that it is qualitatively and quantitatively consistent with the outcome predicted by theory," citing the studies of Gomulkiewicz and Holt (1995), Holt and Gomulkiewicz (1997), Bell (2008) and Orr and Unckless (2008). Hence, there is reason to believe that earth's plants and animals are genetically well prepared to weather the types of rapid climate change that they have, in fact, already encountered and survived in centuries and millennia past.

Bell, G. 2008. Selection, the Mechanism of Evolution. Oxford University Press, Oxford, United Kingdom.

Georghiou, G.P. 1972. The evolution of resistance to pesticides. Annual Review of Ecology and Systematics 3: 133-168.

Gomulkiewicz, R. and Holt, R.D. 1995. When does evolution by natural selection prevent extinction? Evolution 49: 201-207.

Handford, P., Bell, G. and Reimchen, T. 1977. A gillnet fishery considered as an experiment in artificial selection. Journal of the Fisheries Research Board of Canada 34: 954-961.

Holt, R.D. and Gomulkiewicz, R. 1997. The evolution of species niches: a population dynamic perspective. In: Othmer, R.G., Adler, F.R., Lewis, M.A. and Dallon, J.C. (Eds.) Case Studies in Mathematical Modelling: Ecology, Physiology, and Cell Biology. Prentice Hall, Egelwood Cliffs, New Jersey, USA.

Jasieniuk, M., Brule-Babel, A.L. and Morrison, I.N. 1996. The evolution and genetics of herbicide resistance in weeds. Weed Science 44: 176-193.

Kettlewell, H.B.D. 1973. The Evolution of Melanism: The Study of a Recurring Necessity. Oxford University Press, Oxford, United Kingdom.

Levin, B.R., Lipsitch, M., Perrot, V., Schrag, S., Antia, R., Simonsen, L. et al. 1997. The population genetics of antibiotic resistance. Clinical Infectious Diseases 24: S9-S16.

McNeilly, T. and Bradshaw, A.D. 1968. Evolutionary processes in populations of copper tolerant Agrostis tenuis Sibth. Evolution 22: 108-118.

Orr, H.A. and Unckless, R.L. 2008. Population extinction and the genetics of adaptation. American Naturalist 172: 160-169.

Reviewed 16 December 2009