Journal : Exotic invasive plant accumulates native soil pathogens which inhibit native plants

Journal of Ecology

Volume 96 Issue 1 Page 58-67, January 2008

To cite this article: Seema Mangla, Inderjit, Ragan M. Callaway (2008) Exotic invasive plant accumulates native soil pathogens which inhibit native plants
Journal of Ecology 96 (1) , 58–67 doi:10.1111/j.1365-2745.2007.01312.x

Abstract

Exotic invasive plant accumulates native soil pathogens which inhibit native plants

• Seema Mangla ¹¹Centre for Environmental Management of Degraded Ecosystems (CEMDE), University of Delhi, Delhi 110007, India; and ,
• Inderjit ¹*¹Centre for Environmental Management of Degraded Ecosystems (CEMDE), University of Delhi, Delhi 110007, India; and *Correspondence author. E-mail: inderjit@cemde.du.ac.in and
• Ragan M. Callaway ²²Organismal Biology and Ecology, Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA

• ¹Centre for Environmental Management of Degraded Ecosystems (CEMDE), University of Delhi, Delhi 110007, India; and ²Organismal Biology and Ecology, Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA

*Correspondence author. E-mail: inderjit@cemde.du.ac.in

Key-words: allelopathy, Chromolaena odorata, Fusarium, fungal pathogen, indirect interactions, invasion, soil biota, soil pathogen, root leachate

Summary

1.	We investigated the role of a native generalist soil pathogen through which a non-native invasive plant species may suppress naturalized/native plant species.
2.	We found that rhizosphere soils of Chromolaena odorata, one of the world's most destructive tropical invasive weeds, accumulate high concentrations of the generalist soil borne fungi, Fusarium (tentatively identified as F. semitectum), thus creating a negative feedback for native plant species.
3.	Soils collected beneath Chromolaena in the Western Ghats of India inhibited naturalized/native species and contained over 25 times more spores of the pathogenic fungi Fusarium semitectum than soils collected at the same locations beneath neighbouring native species that were at least 20 m from any Chromolaena plant. Sterilization of these soils eliminated their inhibitory effect. Chromolaena root leachate experimentally added to uninvaded soils increased Fusarium spore density by over an order of magnitude, and increased the inhibitory effect of the soils.
4.	The positive effect of Chromolaena root leachates on Fusarium spores was attenuated by activated carbon, suggesting a biochemical basis for how the invader stimulated the pathogen.
5.	Synthesis. Invasive plants have been shown to escape inhibitory soil biota in their native range and to inhibit soil biota in their invaded range, but our results indicate that the impacts of Chromolaena are due to the exacerbation of biotic interactions among native plants and native soil biota, which is to our knowledge a new invasive pathway.