The effect of autocorrelation in environmental variability on the persistence of populations: an experimental test

Despite its significance regarding the conservation and management of biological resources, the body of theory predicting that the correlation between successive environmental states can profoundly influence extinction has not been empirically validated. Identical clonal populations from a model experimental system based on the collembolan Folsomia candida were used in the present study to investigate the effect of environmental autocorrelation on time to extinction. Environmental variation was imposed by variable implementation (present/absent) of a culling procedure according to treatments that represented six patterns of environmental autocorrelation. The average number of culling events was held constant across treatments but, as environmental autocorrelation increased, longer runs of both favourable and unfavourable culling tended to occur. While no difference was found among the survival functions for the various treatments, the time taken for 50% of the component populations to become extinct decreased significantly with increasing environmental autocorrelation. Similarly, analysis of all extinct populations demonstrated that time to extinction was shortened as environmental autocorrelation increased. However, this acceleration of extinction can be fully offset if sequential introduction is used in place of simultaneous introduction when founding the populations.