Gastropod Seed Dispersal: An Invasive Slug Destroys Far More Seeds in Its Gut than Native Gastropods

Tamara Blattmann,Eva Knop,Manfred Türke,Steffen Boch

doi:10.1371/journal.pone.0075243

Tamara Blattmann, Eva Knop + Show 2 more

Open Access

https://doi.org/10.1371/journal.pone.0075243

Copy DOI

Journal: PLoS ONE	Publication Date: Sep 25, 2013
Citations: 49	License type: CC BY 4.0

Affiliation: University of Bern, Technical University of Munich

Abstract

Seed dispersal is one of the most important mechanisms shaping biodiversity, and animals are one of the key dispersal vectors. Animal seed dispersal can directly or indirectly be altered by invasive organisms through the establishment of new or the disruption of existing seed dispersal interactions. So far it is known for a few gastropod species that they ingest and defecate viable plant seeds and consequently act as seed dispersers, referred to as gastropodochory. In a multi-species experiment, consisting of five different plant species and four different gastropod species, we tested with a fully crossed design whether gastropodochory is a general mechanism across native gastropod species, and whether it is altered by the invasive alien slug species Arion lusitanicus. Specifically, we hypothesized that a) native gastropod species consume the seeds from all tested plant species in equal numbers (have no preference), b) the voracious invasive alien slug A. lusitanicus – similarly to its herbivore behaviour – consumes a higher amount of seeds than native gastropods, and that c) seed viability is equal among different gastropod species after gut passage. As expected all tested gastropod species consumed all tested plant species. Against our expectation there was a difference in the amount of consumed seeds, with the largest and native mollusk Helix pomatia consuming most seeds, followed by the invasive slug and the other gastropods. Seed damage and germination rates did not differ after gut passage through different native species, but seed damage was significantly higher after gut passage through the invasive slug A. lusitanicus, and their germination rates were significantly reduced.

Highlights

Animals are important dispersal vectors of plant propagules [1] which is crucial for biodiversity, plant population dynamics, species distributions, and gene flow [2,3,4]
We hypothesized that a) native gastropod species consume the seeds from all tested plant species in equal numbers, b) the voracious invasive alien slug A. lusitanicus – to its herbivore behaviour – consumes a higher amount of seeds than native gastropods, and that c) seed viability is equal among different gastropod species after gut passage
The mean number of consumed seeds was significantly higher for A. lusitanicus compared to the native gastropod species, except for H. pomatia which consumed significantly more seeds of three plant species than A. lusitanicus (Fig. 1, Table S1)

Summary

Introduction

Animals are important dispersal vectors of plant propagules [1] which is crucial for biodiversity, plant population dynamics, species distributions, and gene flow [2,3,4]. Beside various vertebrates and insects, gastropods have been discovered as endozoochorous (transport of propagules inside animals) seed dispersal vectors of propagules [5,6,7,8,9,10]. Invasive alien species successfully establish and spread outside their native range, and they often cause enormous economic costs and ecological damage [13]. They might either directly or indirectly disrupt seed-dispersal interactions. They directly influence the local seed-dispersal mechanism by consuming fruits which would be dispersed by native species [14]. Hansen et al [17] showed that an alien species replaced the dispersal service of a native species which became extinct

Methods

Results

Conclusion