Abstract
The Allee threshold, the critical population density separating growth from decline in populations experiencing strong Allee effects, can vary over space and time but few empirical studies have examined this variation. A lack of geographically extensive, long-term studies on low density population dynamics makes studying variability in Allee effects difficult. We used North American gypsy moth population data from 1996 to 2016 to quantify Allee thresholds in 11 regions of the invasion front. Allee thresholds spanned a continuum from being undetectable due to strong population growth at all densities, to being unmeasurable because populations declined across all densities. The lag-1 temporal autocorrelation in Allee thresholds tended to be negative and spatial synchrony in Allee thresholds extended no further than adjacent regions. This work furthers understanding of spatiotemporal variation in Allee effects using extensive empirical data at the range edge of an invasive insect.
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Data and analysis code are available at https://github.com/jonathan-walter/gmAlleeVar.
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Acknowledgements
The authors thank the Gypsy Moth Slow the Spread program for data and logistical support. JAW was supported by a NatureNet Science Fellowship and USDA-NIFA 2016-67012-24694; KLG by USDA-NIFA 2014-67012-23539; DMJ by NSF DEB-1556767; and PCT by NSF DEB-1556111.
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Walter, J.A., Grayson, K.L., Blackburn, L.M. et al. Spatiotemporal variability in Allee effects of invading gypsy moth populations. Biol Invasions 22, 189–193 (2020). https://doi.org/10.1007/s10530-019-02096-5
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DOI: https://doi.org/10.1007/s10530-019-02096-5