Allelopathic Effects of Native Versus Invasive Plants on One Major Invader.

Gabrielle Thiébaut,Héctor Rodríguez-Pérez,Michèle Tarayre

doi:10.3389/fpls.2019.00854

Abstract

Allelopathy is defined as the effects (stimulatory and inhibitory) of a plant on the development of neighboring plants through the release of secondary compounds. Autoallelophaty is the beneficial or harmful effect of a plant species on itself. The allelopathic potential belonging to a native species could induce a biotic resistance against invasive plants, whereas allelochemicals released by exotic species could favor the establishment of invasive species (invasional meltdown). The aim of our study was to examine the potential allelopathic effect of four plant species on the target species Ludwigia hexapetala using two experiments. In the first experiment, we tested the allelopathic effect of root and leaf leachates of the two congeneric exotic species Ludwigia hexapetala and Ludwigia peploides on L. hexapetala, while in the second experiment, we studied the allelopathic effect of root and leaf leachates of a sympatric exotic species Myriophyllum aquaticum and of one native species Mentha aquatica on L. hexapetala. We measured the stem length to calculate the relative growth rate and four physiological traits (nitrogen balance index and flavonol, chorophyll, anthocyanin indices) of the target plants on a weekly basis. At the end of the experiment, we determined the aboveground and belowground biomass. We also counted the number of lateral branches and measured their lengths. We found that the root leachates of L. peploides and of Myriophyllum aquaticum had stimulated the synthesis of flavonols of L. hexapetala. Leaf leachate of L. hexapetala also stimulated its own flavonol synthesis. Also, the root leachate of L. peploides had stimulated the total biomass and length of lateral branches of L. hexapetala, whereas the production of lateral branches had been stimulated by root leachates of both Ludwigia species and by leaf leachate of Myriophyllum aquaticum. The autoallelopathy of L. hexapetala could explain its invasiveness. Both leachates produced by Mentha aquatica had no effect on the physiological and morphological traits of the invasive L. hexapetala and indicated no biotic resistance in the recipient community. The two invasive plant species Myriophyllum aquaticum and L. peploides could favor the establishment of L. hexapetala. These results suggested an “invasional meltdown.”

Highlights

Many aquatic plant species have been introduced to other continents either accidentally or voluntary for ornamental purposes for example
The root leachate of L. peploides and the leaf leachate of L. hexapetala significantly stimulated the synthesis of flavonols of L. hexapetala after 3 and 4 weeks, respectively
There was no significant effect of both leaf and root leachates of both L. hexapetala and L. peploides on the nitrogen balance index (NBI), chlorophyll, and anthocyanin indices (Figures 1A–D, Table 1)

Summary

Introduction

Many aquatic plant species have been introduced to other continents either accidentally or voluntary for ornamental purposes for example. Susceptibility of an Invader to Allelopathy introduced ranges but coexist with neighbors in their native habitat (Ridenour and Callaway, 2001). Many studies suggest that allelopathy may contribute to the ability of exotic species to form dense stands in invaded ecosystems (Hierro and Callaway, 2003). Many ecosystems often contain combinations of exotic species These communities of invaders could be driven by facilitation or mutualistic interactions between exotic species, according to the theory of “invasional meltdown” (Simberloff and Von Holle, 1999). Plants that have co-evolved with a species with an allelopathic ability may be less susceptible to allelochemicals, while newly exposed species may exhibit less resistance (theory NWH, Callaway and Aschehoug, 2000). Allelochemicals released by native plants could affect the growth of invasive species and would, constitute a biotic resistance against plant invasion (Christina et al, 2015)

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