Methods for estimating long‐distance dispersal

Abstract

Long-distance dispersal (LDD) includes events in which propagules arrive, but do not necessarily establish, at a site far removed from their origin. Although important in a variety of ecological contexts, the system-specific nature of LDD makes ''far removed'' difficult to quantify, partly, but not exclusively, because of inherent uncertainty typically involved with the highly stochastic LDD processes. We critically review the main methods employed in studies of dispersal, in order to facilitate the evaluation of their pertinence to specific aspects of LDD research. Using a novel classification framework, we identify six main methodological groups: biogeographical; Eulerian and Lagrangian movement/redistributional; short-term and long-term genetic analyses; and modeling. We briefly discuss the strengths and weaknesses of the most promising methods available for estimation of LDD, illustrating them with examples from current studies.The rarity of LDD events will continue to make collecting, analyzing, and interpreting the necessary data difficult, and a simple and comprehensive definition of LDD will remain elusive. However, considerable advances have been made in some methodological areas, such as miniaturization of tracking devices, elaboration of stable isotope and genetic analyses, and refinement of mechanistic models. Combinations of methods are increasingly used to provide improved insight on LDD from multiple angles. However, human activities substantially increase the variety of long-distance transport avenues, making the estimation of LDD even more challenging.

Environmental variability and the initiation of dispersal: turbulence strongly increases seed release

“…The quantification of dispersal is a rapidly developing area of research (Levin et al 2003;Nathan et al 2003). For plants, great progress has been made in measurement and modelling of wind dispersal (Greene & Calogeropoulos 2002;Nathan et al 2002;Levin et al 2003).…”

Patterns of pollen dispersal in a small population of Pinus sylvestris L. revealed by total-exclusion paternity analysis

“…Even though this study uses a wider scale than most previous paternity analyses of wind-pollinated trees, the data do not allow reliable estimates of the tail of the distribution, which, as suggested by the observed portion of long-distance immigrants, may extend over tens of kilometres. On the other hand, long-distance dispersal events are likely to be governed by complex stochastic atmospheric processes that are poorly predicted by standard empirical or mechanistic models (Bullock and Clarke, 2000), and they may require novel experimental and analytical approaches (Nathan et al, 2003).…”

The shape of the spatial kernel and its implications for biological invasions in patchy environments

“…[11,12]) studies. In the ecological literature, they are also known as dispersal kernels [3,13], redistribution kernels [14,15], dispersal curves [16] and displacement kernels [17,18], and in epidemiological publications they are sometimes called contact kernels [7,19].…”