When populations are synchronized, they rise and fall together. Analysis of population synchrony and its relationship to distance has played a major role in population ecology but has been absent from most studies of managed populations, such as agricultural arthropods. The extent to which populations at different locations are synchronized reflects the relative roles of shared environmental impacts such as weather and localizing processes such as dispersal. The strength and pattern of synchrony, and the processes generating synchrony, have direct management implications. We bring together two major paths of population ecology research: spatial synchrony of population dynamics, which has been studied across birds, mammals, and insects, and spatial ecology of agricultural arthropod populations. We compare and contrast synchrony of two arthropod species, a spider mite and a leafhopper, at approximately 50 locations across a vineyard region spanning 30 km distances, at within-year (weekly) and between-year time scales over 11 years.
Results/Conclusions
For both species, synchrony is more strongly localized for annual peak abundance across 11 years than it typically is for weekly dynamics within each year's growing season. This suggests that between-year processes such as over-wintering merit greater investigation. Within each year, both localized and region-wide synchrony was found for both species, but leafhoppers showed stronger localization than spider mites, corresponding to their longer generation time and stronger dispersal ability. This demonstrates that the overall herbivore dynamics of the system occur at multiple spatial scales and that the importance of different processes generating synchrony vary by species. The analysis includes new spatiotemporal randomization and bootstrap tests that can be applied to many systems. Our results highlight the value of large-scale, long-term monitoring programs for many kinds of managed populations. They also point toward the potential to test synchrony mechanisms more directly and to synthesize synchrony and landscape analyses.
