Invasive plant Alternanthera philoxeroides suffers more severe herbivory pressure than native competitors in recipient communities.

Shufeng Fan,Haihao Yu,Xianru Dong,Dan Yu,Xiuwen Chen,Chunhua Liu,Ligong Wang

doi:10.1038/srep36542

Abstract

Host-enemy interactions are vital mechanisms that explain the success or failure of invasive plants in new ranges. We surveyed the defoliation of invasive Alternanthera philoxeroides and co-occurring native plants on two islands during different seasons over three consecutive years and measured the leaf nitrogen content and the C/N ratio of each plant species. To evaluate the effects of herbivory on A. philoxeroides, an herbivore exclosure experiment was conducted. We found that the mean defoliation of A. philoxeroides was higher than that of native plants, regardless of whether the dominant species was A. philoxeroides or native plants. A. philoxeroides defoliation increased significantly as the months progressed, whereas the defoliation of the total population of native plants was constant. The leaf nitrogen content was positively correlated with defoliation, and it was highest in A. philoxeroides. Additionally, A. philoxeroides in the herbivore exclusion treatment showed an increase in shoot biomass and total shoot length. Our study revealed that native generalist herbivores prefer the invasive plant to the natives because of the higher leaf nitrogen content. These results support the biotic resistance hypothesis, suggesting that native herbivore species can limit the population spread of invasive plants.

Highlights

The preferences of different herbivores for native vs. exotic plants vary, which might have contributed to the inconsistent results
In China, more than fifteen generalist insects feed on A. philoxeroides[35,36], but there are no reports in the literature discussing the preference of these generalist insects for this invasive species versus native plants or evaluating the effects of native herbivores
The significant species ×season interactions indicated that differences in the defoliation response to seasons varied among A. philoxeroides and the total native plants (Table 1)

Summary

Introduction

The preferences of different herbivores for native vs. exotic plants vary, which might have contributed to the inconsistent results. In China, more than fifteen generalist insects feed on A. philoxeroides[35,36], but there are no reports in the literature discussing the preference of these generalist insects for this invasive species versus native plants or evaluating the effects of native herbivores. We attempted to test three hypotheses: (i) the invasive plant A. philoxeroides will suffer more herbivory damage than the co-occurring native plants in invaded communities, and species dominance will affect the preference of the herbivores for A. philoxeroides vs the native plants; (ii) A. philoxeroides will present higher leaf N concentrations or a lower leaf C/N ratio than the native plants, which will be a contributing factor to its higher defoliation; and (iii) native herbivores will limit the populations of A. philoxeroides. This study contributes to a better understanding of how native herbivores can drive the success of exotic plant species in their new ranges

Methods

Results

Conclusion