Cross-attraction between an exotic and a native pine bark beetle: a novel invasion mechanism?

Min Lu,Daniel R Miller,Jiang-Hua Sun

doi:10.1371/journal.pone.0001302

Abstract

BackgroundAside from the ecological impacts, invasive species fascinate ecologists because of the unique opportunities that invasives offer in the study of community ecology. Some hypotheses have been proposed to illustrate the mechanisms that allow exotics to become invasive. However, positive interactions between exotic and native insects are rarely utilized to explain invasiveness of pests.Methodology/Principal FindingsHere, we present information on a recently formed association between a native and an exotic bark beetle on their shared host, Pinus tabuliformis, in China. In field examinations, we found that 35–40% of P. tabuliformis attacked by an exotic bark beetle, Dendroctonus valens, were also attacked by a native pine bark beetle, Hylastes parallelus. In the laboratory, we found that the antennal and walking responses of H. parallelus to host- and beetle-produced compounds were similar to those of the exotic D. valens in China. In addition, D. valens was attracted to volatiles produced by the native H. parallelus.Conclusions/SignificanceWe report, for the first time, facilitation between an exotic and a native bark beetle seems to involve overlap in the use of host attractants and pheromones, which is cross-attraction. The concept of this interspecific facilitation could be explored as a novel invasive mechanism which helps explain invasiveness of not only exotic bark beetles but also other introduced pests in principle. The results reported here also have particularly important implications for risk assessments and management strategies for invasive species.

Highlights

Invasive species have long fascinated ecologists and invasive biologists, because they can cause tremendous destruction, and because we do not yet understand fully how they can successfully invade novel communities [1,2,3]
We found H. parallelus on roots of P. tabuliformis at both locations in China, with a significant association with attacks by D. valens (ANOVA, F2, 27 = 68.71, P,0.001 at the Tunlanchuan Forest Station; F2, 27 = 57.41 at Yaopin Forest Station, P,0.001)
Healthy pines with no evidence of attacks by D. valens had low numbers of roots infested by H. parallelus (,0.05%), with approximately one adult beetle on each attacked root (Fig. 1A–B)

Summary

Introduction

Invasive species have long fascinated ecologists and invasive biologists, because they can cause tremendous destruction, and because we do not yet understand fully how they can successfully invade novel communities [1,2,3]. Facilitation between exotic and native invertebrates has received much less attention the relevance of facilitation may be important, especially when several invasion mechanisms work in synergy [7,8,9] This may be true for bark beetles (Coleoptera: Scolytidae) that breed in the phloem tissue of coniferous trees, often in multiple-species associations [10]. For the first time, facilitation between an exotic and a native bark beetle seems to involve overlap in the use of host attractants and pheromones, which is cross-attraction The concept of this interspecific facilitation could be explored as a novel invasive mechanism which helps explain invasiveness of exotic bark beetles and other introduced pests in principle. The results reported here have important implications for risk assessments and management strategies for invasive species

Objectives

Methods

Results

Conclusion