Population Ecology

, Volume 48, Issue 2, pp 131–138

Geographic variation in density-dependent dynamics impacts the synchronizing effect of dispersal and regional stochasticity

  • Andrew M. Liebhold
  • Derek M. Johnson
  • Ottar N. Bjørnstad
Original Article

Abstract

Explanations for the ubiquitous presence of spatially synchronous population dynamics have assumed that density-dependent processes governing the dynamics of local populations are identical among disjunct populations, and low levels of dispersal or small amounts of regionalized stochasticity (“Moran effect”) can act to synchronize populations. In this study we used historical spatially referenced data on gypsy moth (Lymantria dispar) outbreaks to document that density-dependent processes can vary substantially across geographical landscapes. This variation may be due in part to geographical variation in habitat (e.g., variation in forest composition). We then used a second-order log-linear stochastic model to explore how inter-population variation in density-dependent processes affects synchronization via either synchronous stochastic forcing or dispersal. We found that geographical variation in direct density-dependence (first order) greatly diminishes synchrony caused by stochasticity but only slightly decreases synchronization via dispersal. Variation in delayed density-dependence (second order) diluted synchrony caused by regional stochasticity to a lesser extent than first-order variation, but it did not have any influence on synchrony caused by dispersal. In general, synchronization caused by dispersal was primarily dependent upon the instability of populations and only weakly, if at all, affected by similarities in density-dependence among populations. We conclude that studies of synchrony should carefully consider both the nature of the synchronizing agents and the pattern of local density-dependent processes, including how these vary geographically.

Keywords

Spatial synchrony Moran effect Gypsy moth Population cycle Stability Lymantria dispar Outbreak 

Supplementary material

10144_2005_248_ESM_supp.pdf (91 kb)
(PDF 92 KB)

Copyright information

© The Society of Population Ecology and Springer-Verlag Tokyo 2006

Authors and Affiliations

  • Andrew M. Liebhold
    • 1
  • Derek M. Johnson
    • 2
  • Ottar N. Bjørnstad
    • 3
  1. 1.USDA Forest ServiceNortheastern Research StationMorgantownUSA
  2. 2.Department of BiologyUniversity of LouisianaMonroeUSA
  3. 3.ASI 501, Departments of Entomology and BiologyPennsylvania State UniversityUniversity Park USA

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