Environmental variability can select for optimism or pessimism.
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.
School of Mathematics, University of Bristol, University Walk, Bristol BS8 1TW, UK. john.mcnamara@bristol.ac.uk
John M
JM
McNamara
Pete C
PC
Trimmer
Anders
A
Eriksson
James A R
JA
Marshall
Alasdair I
AI
Houston
D000818:Animals; D005075:Biological Evolution; D004777:Environment; D008954:Models, Biological; D011157:Population Dynamics; D012098:Reproduction; D012641:Selection, Genetic