Environmental variability can select for optimism or pessimism |
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Authors: | McNamara John M Trimmer Pete C Eriksson Anders Marshall James A R Houston Alasdair I |
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Institution: | School of Mathematics, University of Bristol, University Walk, Bristol BS8 1TW, UK. john.mcnamara@bristol.ac.uk |
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Abstract: | We propose operational definitions of reproductive optimism and pessimism; optimism involves behaving in a way that gives too much weight (in terms of producing surviving offspring) to positive events, pessimism gives too much weight to negative events. Natural selection maximizes the long-term growth of a lineage rather than short-term measures such as numbers of offspring. Consequently, optimism or pessimism can be favoured by natural selection, even though such biases appear irrational from a short-term perspective. We investigate the evolution of optimism in a metapopulation. The circumstances of a patch change over time, independently of other patches. With sufficient dispersal between patches, stochasticity affects members of a lineage largely independently and optimism is favoured. With little dispersal, the temporal fluctuations of a patch affect many members similarly; pessimism is then favoured. Our results establish that the spatial and temporal structure of the environment is crucial in determining the direction of evolved biases. |
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Keywords: | Metapopulation natural selection optimism rationality spatial variation stochasticity temporal variation |
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