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

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.

Effect of density-dependent individual movement on emerging spatial population distribution: Brownian motion vs Levy flights

“…Whilst considerable progress has been done over the last two decades in the understanding of this phenomenon [45,51,52,59], the effect of many relevant factors on the ecological pattern formation remains obscure and many questions yet wait to be answered, so that the problem remains to be a focus of research and discussion [65]. In particular, the role of individual movement behavior remains poorly understood, in spite of arguably being a key factor in spatial ecology [10,57]. Here we attempted to relate the problem of understanding of populations spatial patterning to another major focus in ecology, namely, to the effect of different individual movement patterns [68,84,89].…”

Individual differences in dominance-related traits drive dispersal and settlement in hatchery-reared juvenile brown trout

“…Dispersal is a central issue for the understanding of evolutionary processes and population dynamics 1 , 2 , with profound implications for current spatial distributions, local population densities, demographic dynamics, and the genetics of spatially-structured populations 3 – 5 . Moreover, dispersal processes are important because of their implications for forecasting animal distributions and for robust decision-making in the areas of resource management and conservation of biodiversity 6 .…”

Three-dimensional random walk models of individual animal movement and their application to trap counts modelling

“…All species change their location in space at least during some stages of their life. Movement is known to have fundamental implications for individual survival, behaviours and reproduction, the population dynamics, and on fitness and evolution (Clobert et al, 2001;Bullock et al, 2002). The capacity for movement is prolific across different species.…”