Alien plant species on roadsides of the northwestern Patagonian steppe (Argentina).

Giselle Ailin Chichizola,Adriana Edit Rovere,Sofía Laura Gonzalez

doi:10.1371/journal.pone.0246657

Abstract

The introduction of alien species represents one of the greatest threats to biodiversity worldwide. Highway construction increases the dispersal and invasion of exotic plant species. This study examined the assembly process of the plant communities to determine whether the roadsides of the Patagonian steppe represent a reservoir and dispersal source of invasive exotic species. We analyzed the composition of exotic and native species and functional groups present in the established vegetation and seed banks of roadsides and reference areas nearby. The type of dispersal of exotic and native species at the roadsides was also evaluated. Total cover and that of exotic and native species was lower at the roadsides than in the reference areas; however, at the roadsides the cover and seed abundance of exotic species was higher than that of native species. In the roadsides vegetation, native shrubs such as Acaena splendens predominated, along with exotic perennial herbs and grasses which were mainly represented by Rumex acetosella. In the seed bank the predominant species were exotic perennial herbs, also represented by R. acetosella, annual exotic species such as Epilobium brachycarpum and Verbascum thapsus, and annual native species such as Heliotropium paronychioides. No exotic shrubs were found either at the roadsides or in the reference areas. The species at the roadsides did not present a dominant type of dispersal. The abundance of exotic species at the roadsides, both in the aboveground vegetation and the seed bank, may be due to the stressful environment and the characteristics of the species themselves, such as the ability to form seed banks. This work revealed that the roadsides of the Patagonian steppe constitute reservoirs of invasive exotic species, highlighting the importance of identifying them and controlling their spread, with a view to generating ecosystem management programs.

Highlights

The introduction of alien species represents one of the major threats to biodiversity at a global level [1]
Once successfully introduced outside their natural range, potentially invasive exotic plant species can propagate in the new environment if their ecological needs are met, establishing self-sustaining populations [5]
A total of 53 plant species belonging to 47 genera and 25 families were found in the vegetation and seed bank at the roadsides (RS) and the reference areas (RA)

Summary

Introduction

The introduction of alien species represents one of the major threats to biodiversity at a global level [1]. Exotic species can transform a habitat, affecting biodiversity on different spatial scales, contributing to species extinction [2] and creating severe challenges in terms of their management and control [3]. More homogeneous habitats are created at the roadsides, affecting microclimatic conditions and causing considerable reduction in competition, where fast-growing ruderal species with high seed production generally become established, many of which are exotic [8, 9]. These habitats may represent a starting point for the dispersal of some exotic species, enabling them to spread and extend their distribution to non-degraded natural habitats [10]. The colonizing potential of a species and its persistence in the invaded environment depend on its ability to overcome environmental and dispersal barriers, aspects which are related to its reproductive and dispersal characteristics [14]

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Conclusion