Human‐mediated dispersal and disturbance shape the metapopulation dynamics of a long‐lived herb

Bullock, James M. ORCID:; Wichmann, Matthias C.; Hails, Rosemary S.; Hodgson, David J.; Alexander, Matt J.; Morley, Kathryn; Knopp, Tatyana; Ridding, Lucy E.; Hooftman, Danny A.P.. 2020 Human‐mediated dispersal and disturbance shape the metapopulation dynamics of a long‐lived herb. Ecology, 101 (8), e03087. 14, pp.

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As anthropogenic impacts on the natural world escalate, there is increasing interest in the role of humans in dispersing seeds. But the consequences of this Human‐Mediated Dispersal (HMD) on plant spatial dynamics are little studied. In this paper, we ask how secondary dispersal by HMD affects the dynamics of a natural plant metapopulation. In addition to dispersal between patches, we suggest within‐patch processes can be critical. To address this, we assess how variation in local population dynamics, caused by small‐scale disturbances, affects metapopulation size. We created an empirically based model with stochastic population dynamics and dispersal among patches, which represented a real‐world, cliff‐top metapopulation of wild cabbage Brassica oleracea. We collected demographic data from multiple populations by tagging plants over eight years. We assessed seed survival, and establishment and survival of seedlings in intact vegetation vs. small disturbances. We modeled primary dispersal by wind using field data and used experimental data on secondary HMD by hikers. We monitored occupancy patterns over a 14‐yr period in the real metapopulation. Disturbance had large effects on local population growth rates, by increasing seedling establishment and survival. This meant that the modeled metapopulation grew in size only when the area disturbed in each patch was above 35%. In these growing metapopulations, although only 0.2% of seeds underwent HMD, this greatly enhanced metapopulation growth rates. Similarly, HMD allowed more colonizations in declining metapopulations under low disturbance, and this slowed the rate of decline. The real metapopulation showed patterns of varying patch occupancy over the survey years, which were related to habitat quality, but also positively to human activity along the cliffs, hinting at beneficial effects of humans. These findings illustrate that realistic changes to dispersal or demography, specifically by humans, can have fundamental effects on the viability of a species at the landscape scale.

Item Type: Publication - Article
Digital Object Identifier (DOI):
UKCEH and CEH Sections/Science Areas: Biodiversity (Science Area 2017-)
UKCEH Fellows
ISSN: 0012-9658
Additional Information. Not used in RCUK Gateway to Research.: Open Access paper - full text available via Official URL link.
Additional Keywords: anthropogenic, colonization, demography, extinction, human-vectored dispersal, long-distance dispersal, spatial dynamics, stochasticity
NORA Subject Terms: Ecology and Environment
Date made live: 08 Jul 2020 16:18 +0 (UTC)

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