The total dispersal kernel: a review and future directions

Abstract

The distribution and abundance of plants across the world depends in part on their ability to move, which is commonly characterized by a dispersal kernel. For seeds, the total dispersal kernel (TDK) describes the combined influence of all primary, secondary and higher-order dispersal vectors on the overall dispersal kernel for a plant individual, population, species or community. Understanding the role of each vector within the TDK, and their combined influence on the TDK, is critically important for being able to predict plant responses to a changing biotic or abiotic environment. In addition, fully characterizing the TDK by including all vectors may affect predictions of population spread. Here, we review existing research on the TDK and discuss advances in empirical, conceptual modelling and statistical approaches that will facilitate broader application. The concept is simple, but few examples of well-characterized TDKs exist. We find that significant empirical challenges exist, as many studies do not account for all dispersal vectors (e.g. gravity, higher-order dispersal vectors), inadequately measure or estimate long-distance dispersal resulting from multiple vectors and/or neglect spatial heterogeneity and context dependence. Existing mathematical and conceptual modelling approaches and statistical methods allow fitting individual dispersal kernels and combining them to form a TDK; these will perform best if robust prior information is available. We recommend a modelling cycle to parameterize TDKs, where empirical data inform models, which in turn inform additional data collection. Finally, we recommend that the TDK concept be extended to account for not only where seeds land, but also how that location affects the likelihood of establishing and producing a reproductive adult, i.e. the total effective dispersal kernel.

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

“…There is a need to understand better the degree to which humans disperse different species, and its impact on populations, metapopulations and metacommunities. One way forward may be to consider dispersal by humans in the context of the Total Dispersal Kernel, TDK (Rogers et al 2019). The TDK describes the combined contribution of all dispersal vectors to an overall dispersal kernel, and this concept encourages researchers to consider the full range of dispersal processes in a system.…”

Rapid changes in seed dispersal traits may modify plant responses to global change

“…To illustrate some of the population and community level impacts that changes in dispersal traits can have, we discuss changes in plant traits, changes in external conditions and changes in animal disperser traits. Including animal dispersers not only gives a more complete picture of the systems in which rapid responses in dispersal are addressed (even if the mechanisms may be different), but also demonstrates how seed dispersal can be affected when biotic dispersal vectors respond to environmental changes and thus influence the total dispersal kernel (Rogers et al , this issue-b). To be comparable with plant dispersal, we consider animal movement broadly, including such topics as natal dispersal, seasonal migration, foraging movement, settlement behaviour and movements within home ranges.…”

How far might plant-eating dinosaurs have moved seeds?

“…effect on germination) which is difficult, if not impossible, to infer from the fossil record. Most plant species are dispersed by multiple vectors, passive and active, which form the total dispersal kernel [39]. From the plant perspective, understanding the total seed dispersal kernel requires considering multiple dispersal vectors and hence, for 10 100 1000 10 000 100 000 10 100 1000 10 000 100 000 10 100 1000 10 000 100 000 10 100 1000 10 000 100 000 Figure 2.…”