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The role of indirect interspecific effects in the stochastic dynamics of a simple trophic system
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  • Laura Bartra-Cabré,
  • Brage Hansen,
  • Aline Magdalena Lee,
  • Kate Layton-Matthews,
  • Maarten Loonen,
  • Eva Fuglei,
  • Leif Loe,
  • Vidar Grøtan
Laura Bartra-Cabré
Norwegian University of Science and Technology

Corresponding Author:laurabc9@gmail.com

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Brage Hansen
Norwegian Institute for Nature Research
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Aline Magdalena Lee
Norges teknisk-naturvitenskapelige universitet
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Kate Layton-Matthews
Norwegian Institute for Nature Research
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Maarten Loonen
University of Groningen
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Eva Fuglei
Norwegian Polar Institute
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Leif Loe
Norwegian University of Life Sciences
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Vidar Grøtan
Norwegian University of Science and Technology
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Abstract

Understanding indirect interspecific effects (IIEs) on population dynamics is key for predicting community dynamics. Yet, empirically teasing apart IIEs from other interactions and population drivers is data-demanding. We used stochastic population models parameterized with long-term vital rate time series to simulate population trajectories and examine IIEs in a high-arctic vertebrate trophic chain: Svalbard reindeer, its scavenger (Arctic fox), and a migratory fox prey (barnacle goose). Reindeer carcass supply shaped fox abundance fluctuations, subsequently affecting goose fluctuations. Yet reindeer and goose population growth rates were only weakly correlated, probably due to stochasticity, density dependence and life history traits. However, by isolating the effects of individual processes within our simulation model, we demonstrate the presence of strong IIEs on goose population fluctuations and extinction probability. Thus, we highlight the long-term impact of species interactions, including IIEs, on species coexistence and communities, beyond immediate effects and short-term fluctuations.