Retention time variability as a mechanism for animal mediated long-distance dispersal.

Vishwesha Guttal,Frederic Bartumeus,Gregg Hartvigsen,Andrew L Nevai,Jeffrey A Harvey

doi:10.1371/journal.pone.0028447

Abstract

Long-distance dispersal (LDD) events, although rare for most plant species, can strongly influence population and community dynamics. Animals function as a key biotic vector of seeds and thus, a mechanistic and quantitative understanding of how individual animal behaviors scale to dispersal patterns at different spatial scales is a question of critical importance from both basic and applied perspectives. Using a diffusion-theory based analytical approach for a wide range of animal movement and seed transportation patterns, we show that the scale (a measure of local dispersal) of the seed dispersal kernel increases with the organisms' rate of movement and mean seed retention time. We reveal that variations in seed retention time is a key determinant of various measures of LDD such as kurtosis (or shape) of the kernel, thinkness of tails and the absolute number of seeds falling beyond a threshold distance. Using empirical data sets of frugivores, we illustrate the importance of variability in retention times for predicting the key disperser species that influence LDD. Our study makes testable predictions linking animal movement behaviors and gut retention times to dispersal patterns and, more generally, highlights the potential importance of animal behavioral variability for the LDD of seeds.

Highlights

Dispersal is the unidirectional movement of an organism, or its reproductive unit, away from the place of its origin [1]
We determine how an absolute measure of long-distance dispersal (LDD), defined as the number of seeds falling beyond a threshold distance, is influenced by seed retention time patterns
We present an analytical model that makes testable predictions relating animal movement behavior and seed retention time characteristics to seed dispersal patterns

Summary

Introduction

Dispersal is the unidirectional movement of an organism, or its reproductive unit (e.g., seeds), away from the place of its origin [1]. While short-distance dispersal has been well studied for a long time, it is only relatively recently that the significance of the basic as well as applied aspects of LDD in ecology [1] and epidemiology [7] have been well recognized. This has led to a surge in empirical and theoretical studies to device quantitative measures of LDD events. The kurtosis, or the shape, of the kernel measures the distribution of the probability density at both the peak and tails of the kernel [12]

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