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Bullock JM, Wichmann MC, Hails RS, Hodgson DJ, Alexander MJ, Morley K, Knopp T, Ridding LE, Hooftman DAP. Human-mediated dispersal and disturbance shape the metapopulation dynamics of a long-lived herb. Ecology 2020; 101:e03087. [PMID: 32320472 DOI: 10.1002/ecy.3087] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 02/12/2020] [Accepted: 03/30/2020] [Indexed: 11/11/2022]
Abstract
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.
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Affiliation(s)
- James M Bullock
- UK Centre for Ecology & Hydrology, Benson Lane, Wallingford, Oxfordshire, OX10 8BB, United Kingdom
| | - Matthias C Wichmann
- UK Centre for Ecology & Hydrology, Benson Lane, Wallingford, Oxfordshire, OX10 8BB, United Kingdom.,Heinz Sielmann Stiftung, Unter den Kiefern 9, 14641, Wustermark, OT Elstal, Germany
| | - Rosemary S Hails
- UK Centre for Ecology & Hydrology, Benson Lane, Wallingford, Oxfordshire, OX10 8BB, United Kingdom.,National Trust, Heelis, Kemble Drive, Swindon, SN2 2NA, United Kingdom
| | - David J Hodgson
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn, TR10 9FE, United Kingdom
| | - Matt J Alexander
- UK Centre for Ecology & Hydrology, Benson Lane, Wallingford, Oxfordshire, OX10 8BB, United Kingdom
| | - Kathryn Morley
- Defra, 2 Marsham Street, London, SW1P 4DF, United Kingdom
| | - Tatjana Knopp
- UK Centre for Ecology & Hydrology, Benson Lane, Wallingford, Oxfordshire, OX10 8BB, United Kingdom
| | - Lucy E Ridding
- UK Centre for Ecology & Hydrology, Benson Lane, Wallingford, Oxfordshire, OX10 8BB, United Kingdom
| | - Danny A P Hooftman
- UK Centre for Ecology & Hydrology, Benson Lane, Wallingford, Oxfordshire, OX10 8BB, United Kingdom.,Lactuca: Environmental Data Analyses and Modelling, Diemen, 1112NC, The Netherlands
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