Measuring and testing for spatial synchrony

Spatial synchrony in abundance among populations at different locations has been studied for many species. Different statistics have been used as meas ures of synchrony, and various techniques have been employed to test the hy pothesis that there is no synchrony. In this paper we first describe and co ntrast various measures of synchrony and then discuss testing for no synchr ony. Tests that ignore the serial correlation are commonly employed but are incorrect if there is serial correlation present, as is often the case wit h populations followed over time. Alternative approaches and their limitati ons are presented including tests based on residuals, adjusted degrees of f reedom tests, and bootstrap procedures. We recommend tests based on residua ls in a model-based setting. We also discuss some of the difficulties of fi nding model-free approaches and suggest some methods based on confidence in tervals for future study.