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Occupancy versus colonisation-extinction models for projecting population trends at different spatial scales
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  • Jenni Nordén,
  • Philip Harrison,
  • Louise Mair,
  • Juha Siitonen,
  • Anders Lundström,
  • Oskar Kindvall,
  • Tord Snall
Jenni Nordén
Norwegian Institute for Nature Research Oslo
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Philip Harrison
Uppsala University
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Louise Mair
Newcastle University
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Juha Siitonen
Natural Resources Institute Finland
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Anders Lundström
Swedish University of Agricultural Sciences
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Oskar Kindvall
Calluna AB
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Tord Snall
Sveriges lantbruksuniversitet
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Abstract

Understanding spatiotemporal population trends and their drivers is a key aim in population ecology. We further need to be able to predict how the dynamics and sizes of populations are affected in the long term by changing landscapes and climate. However, predictions of future population trends are sensitive to a range of modelling assumptions. Deadwood-dependent fungi are an excellent system for testing the performance of different predictive models of sessile species as these species have different rarity and spatial population dynamics, the populations are structured at different spatial scales and they utilize distinct substrates. We tested how the projected large scale occupancies of species with differing landscape-scale occupancies are affected over the coming century by different modelling assumptions. We compared projections based on occupancy models against colonization-extinction models, conducting the modelling at alternative spatial scales, and using fine or coarse resolution deadwood data. We also tested effects of key explanatory variables on species occurrence and colonization-extinction dynamics. The hierarchical Bayesian models applied were fitted to an extensive repeated survey of deadwood and fungi at 174 patches. We projected higher occurrence probabilities and more positive trends using the occupancy models compared to the colonisation-extinction models, with greater difference for the species with lower occupancy, colonization rate and colonization:extinction ratio than for the species with higher estimates of these statistics. The magnitude of future increase in occupancy depended strongly on the spatial modelling scale and resource resolution. We encourage using colonisation-extinction models over occupancy models, modelling the process at the finest resource-unit resolution that is utilizable by the species, and conducting projections for the same spatial scale and resource resolution at which the model fitting is conducted. Further, the models applied should include key variables driving the metapopulation dynamics, such as the availability of suitable resource units, habitat quality and spatial connectivity.

Peer review status:ACCEPTED

17 Jan 2020Submitted to Ecology and Evolution
21 Jan 2020Assigned to Editor
21 Jan 2020Submission Checks Completed
21 Jan 2020Review(s) Completed, Editorial Evaluation Pending
04 Feb 2020Editorial Decision: Accept