Spatial variation in branch size promotes metapopulation persistence in dendritic river networks |
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Authors: | Chaoqun Ma Yang Shen Daniel Bearup William F. Fagan Jinbao Liao |
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Affiliation: | 1. Ministry of Educations Key Laboratory of Poyang Lake Wetland and Watershed Research, School of Geography and Environment, Jiangxi Normal University, Nanchang, China;2. School of Mathematics, Statistics and Actuarial Sciences, University of Kent, Canterbury, U.K.;3. Department of Biology, University of Maryland, College Park, MD, U.S.A. |
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Abstract: | - Despite years of attention, the dynamics of species constrained to disperse within riverine networks are not well captured by existing metapopulation models, which often ignore local dynamics within branches.
- We develop a modelling framework, based on traditional metapopulation theory, for patch occupancy dynamics subject to local colonisation–extinction dynamics within branches and regional dispersal between branches in size-structured, bifurcating riverine networks. Using this framework, we investigate whether and how spatial variation in branch size affects species persistence for dendritic systems with directional dispersal, including one-way (up- or downstream only) and two-way (both up- and downstream) dispersal.
- Variation in branch size generally promotes species persistence more obviously at higher relative extinction rate, suggesting that previous studies ignoring differences in branch size in real riverine systems might overestimate species extinction risk.
- Two-way dispersal is not always superior to one-way dispersal as a strategy for metapopulation persistence especially at high relative extinction rate. The type of dispersal that maximises species persistence is determined by the hierarchical level of the largest, and hence most influential, branch within the network. When considering the interactive effects of up- and downstream dispersal, we find that moderate upstream-biased dispersal maximises metapopulation viability, mediated by spatial branch arrangement.
- Overall, these results suggest that both branch-size variation and species traits interact to determine species persistence, theoretically demonstrating the ecological significance of their interplay.
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Keywords: | downstream dispersal local branch dynamics metapopulation model spatial branch-size heterogeneity upstream dispersal |
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