Abstract
As the single opportunity for plants to move, seed dispersal has an important impact on plant fitness, species distributions and patterns of biodiversity. However, models that predict dynamics such as risk of extinction, range shifts and biodiversity loss tend to rely on the mean value of parameters and rarely incorporate realistic dispersal mechanisms. By focusing on the mean population value, variation among individuals or variability caused by complex spatial and temporal dynamics is ignored. This calls for increased efforts to understand individual variation in dispersal and integrate it more explicitly into population and community models involving dispersal. However, the sources, magnitude and outcomes of intraspecific variation in dispersal are poorly characterized, limiting our understanding of the role of dispersal in mediating the dynamics of communities and their response to global change. In this manuscript, we synthesize recent research that examines the sources of individual variation in dispersal and emphasize its implications for plant fitness, populations and communities. We argue that this intraspecific variation in seed dispersal does not simply add noise to systems, but, in fact, alters dispersal processes and patterns with consequences for demography, communities, evolution and response to anthropogenic changes. We conclude with recommendations for moving this field of research forward.
Highlights
For most plants, seed dispersal represents the main opportunity to move and has an important impact on plant fitness, species distributions, community composition and patterns of biodiversity (e.g. Merritt et al 2010; Vellend 2010; Kroiss and Hillerslambers 2015)
We propose that intraspecific variation in seed dispersal has important implications for our understanding of plant fitness, as well as population, community and landscape dynamics
In contrast to their Gaussian counterparts, these kernels have higher probabilities of short-distance dispersal events, creating a more peaked distribution, and higher probabilities of rare, long-distance dispersal events, creating a fatter or thicker tail (Box 4). These dispersal kernels preserve the mean distance travelled by a seed, but lead to faster rates of either constant or ever-accelerating spatial spread (Box 4). These population-level leptokurtic kernels could arise due to intraspecific variation in seed dispersal (Box 2), and have been the focus of numerous studies (Neubert and Caswell 2000; Petrovskii and Morozov 2009; Bouin et al 2012; Stover et al 2014; Horvitz et al 2015; Schreiber and Beckman, 2019)
Summary
For most plants, seed dispersal represents the main opportunity to move and has an important impact on plant fitness, species distributions, community composition and patterns of biodiversity (e.g. Merritt et al 2010; Vellend 2010; Kroiss and Hillerslambers 2015). These dispersal kernels preserve the mean distance travelled by a seed, but lead to faster rates of either constant or ever-accelerating spatial spread (Box 4) These population-level leptokurtic kernels could arise due to intraspecific variation in seed dispersal (Box 2), and have been the focus of numerous studies (Neubert and Caswell 2000; Petrovskii and Morozov 2009; Bouin et al 2012; Stover et al 2014; Horvitz et al 2015; Schreiber and Beckman, 2019). As discussed above, ignoring intraspecific variation in seed dispersal can underestimate population spread rates This is critical for predicting future range shifts, as the ability of plants to track rapid changes in climate remains largely uncertain There are many exciting research directions that can be pursued with the use of field (e.g. observational, experimental) studies, modelling studies (e.g. statistical, computational, mathematical) and their interface
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