DOI: 10.5061/dryad.j6h230v
title: Data from: Population spatial synchrony enhanced by periodicity and low detuning with environmental forcing

description: Explaining why fluctuations in abundances of spatially disjunct
 populations often are correlated through time is a major goal of
 population ecologists. We address two hypotheses receiving little to no
 testing in wild populations: a) that population cycling facilitates
 synchronization given weak coupling among populations, and b) that the
 ability of periodic external forces to synchronize oscillating populations
 is a function of the mismatch in timescales (detuning) between the force
 and the population. Here, we apply new analytical methods to field survey
 data on gypsy moth outbreaks. We report that at timescales associated with
 gypsy moth outbreaks, spatial synchrony increased with population
 periodicity via phase locking. The extent to which synchrony in
 temperature and precipitation influenced population synchrony was
 associated with the degree of mismatch in dominant timescales of
 oscillation. Our study provides new empirical methods and rare empirical
 evidence that population cycling and low detuning can promote population
 spatial synchrony.
description: Defoliation
 DataThe data are the annual
 proportion of land area defoliated by gypsy moths across the Northeastern
 United States for 1990-2015. Defoliation was mapped with aerial surveys
 conducted by each state. Frequency of defoliation (0/1) in 1 × 1 km
 rasters was aggregated into 8 × 8 km grid cells. The data are limited to
 1,327 focal grid cells in which defoliation was detected in 4 or more
 years both in the focal grid cell and at least 1 of the 8 nearest
 neighbour grid cells. The column headings “xcoord” and “ycoord” are
 coordinates expressed in meters based on the NAD 1983 Albers Projection,
 Central Meridian &gt; -96, Standard Parallel 1 = 20, Standard Parallel 2 =
 60, Latitude Of Origin = 40 and Datum = D North American 1983. The
 remaining columns are years 1990-2015.PRISM weather
 dataThis file contains
 weather data derived from the the PRISM Climate Group, Oregon State
 University (http://prism.oregonstate.edu), spatially referenced within 8 ×
 8 km grid cells. The cells in this data are limited to 1,327 focal grid
 cells in which gypsy moth defoliation was detected in 4 or more years both
 in the focal grid cell and at least 1 of the 8 nearest neighbour grid
 cells. The first set of columns are weather variables abbreviated as
 “tmax” (mean maximum temperature, “tmin” = mean minimum temperature, and
 “ppt” = precipitation. The month for weather variable is given as 01-12
 (January – December). Temperature is in units of degrees Celsius and
 precipitation is in millimeters. The column headings “xcoord” and “ycoord”
 are coordinates expressed in meters based on the NAD 1983 Albers
 Projection, Central Meridian &gt; -96, Standard Parallel 1 = 20, Standard
 Parallel 2 = 60, Latitude Of Origin = 40 and Datum = D North American
 1983. The remaining columns are years 1990-2015.R code for
 wavelet_ncLISA functionCode by Jonathan Walter,
 borrowing from Ottar Bjornstad's 'ncf' package, with
 dependencies on Dan Reuman's 'wsyn' package for measuring
 local cross-wavelet synchrony.R Code
 localPhaseSynch_pairwise functionCode by Jonathan Walter,
 borrowing from Ottar Bjornstad's 'ncf' package, with
 dependencies on Dan Reuman's 'wsyn' package and the
 'circular' package for measuring local phase
 synchrony.