Are Introduced Species Better Dispersers Than Native Species? A Global Comparative Study of Seed Dispersal Distance

Habacuc Flores-Moreno,Fiona J Thomson,Angela T Moles,David I Warton,Nina Farwig

doi:10.1371/journal.pone.0068541

Habacuc Flores-Moreno, Fiona J Thomson + Show 3 more

Open Access

https://doi.org/10.1371/journal.pone.0068541

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Journal: PloS one	Publication Date: Jun 20, 2013
Citations: 84	License type: CC BY 4.0

Affiliation: UNSW Sydney, Manaaki Whenua – Landcare Research

Abstract

We provide the first global test of the idea that introduced species have greater seed dispersal distances than do native species, using data for 51 introduced and 360 native species from the global literature. Counter to our expectations, there was no significant difference in mean or maximum dispersal distance between introduced and native species. Next, we asked whether differences in dispersal distance might have been obscured by differences in seed mass, plant height and dispersal syndrome, all traits that affect dispersal distance and which can differ between native and introduced species. When we included all three variables in the model, there was no clear difference in dispersal distance between introduced and native species. These results remained consistent when we performed analyses including a random effect for site. Analyses also showed that the lack of a significant difference in dispersal distance was not due to differences in biome, taxonomic composition, growth form, nitrogen fixation, our inclusion of non-invasive introduced species, or our exclusion of species with human-assisted dispersal. Thus, if introduced species do have higher spread rates, it seems likely that these are driven by differences in post-dispersal processes such as germination, seedling survival, and survival to reproduction.

Highlights

It has often been suggested that introduced and/or invasive species have greater natural dispersal abilities than do native or less invasive species [1,2,3,4]
Thompson and Davis [5] state that research on traits of invasive plants “has revealed that, when compared with natives or non-invasive aliens, invasive aliens ...produce more seeds that are better dispersed...”, and Ordonez and Olff [4] state that “ analyses comparing regional and global species pools of natives and aliens have found that aliens .... produce more seeds that are better dispersed...”
Once we have accounted for the effect of seed mass, plant height and dispersal syndrome, there is no significant difference in mean seed dispersal distance between native and introduced species

Summary

Introduction

It has often been suggested that introduced and/or invasive species have greater natural dispersal abilities than do native or less invasive species [1,2,3,4]. The idea that introduced species disperse their seeds better than natives species underpins much of our understanding of the dynamics of introduced species, including rates of spread [6,7,8], range sizes [6,7,9] and the ability of introduced species to take advantage of colonization opportunities arising from disturbance and/or an increase in resource levels [10,11,12,13]. We provide the first general test of the fundamental idea that introduced plant species achieve greater dispersal distances under natural conditions than do native species. The few studies that have compared actual dispersal distances between pairs or small sets of introduced and co-occurring native species have found conflicting results, reporting introduced species to have greater seed dispersal distances than native species [19], or no significant difference between introduced and native species [20,21]

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