New Communities on Eucalypts Grown Outside Australia

Sarah Mansfield

doi:10.3389/fpls.2016.01812

Abstract

The expansion of eucalypt forestry worldwide has been accompanied by accidental and deliberate introductions of Australian insects associated with eucalypts. Local insect species have also colonized introduced eucalypts in many regions. This situation provides a unique opportunity to observe the development of new insect communities across trophic levels. Here the history of Australian invaders and native colonizers on eucalypts outside Australia is reviewed from the perspective of herbivore guilds: leaf chewers, sap suckers, wood borers, gall formers, termites. Historical patterns of invasion are identified across these guilds. Very few species of Australian leaf chewers, wood borers or termites have become widespread but these guilds are proportionately high in native colonizers. In contrast, sap suckers have multiple invasive species globally with relatively fewer native colonizers. The gall former guild also has several invasive species but so far includes no native colonizers, perhaps due to their tendency to have highly specific host plant associations. Natural enemies of Australian invaders are also members of new eucalypt insect communities, partly through planned biological control programs, but the rate of accidental introductions at higher trophic levels is increasing steadily. At the same time, local natural enemies enter eucalypt communities either to form new associations with Australian invaders or to follow native colonizers into this new habitat. Australian sap suckers have attracted far more new associations than other guilds so far. Native leaf chewers have often been followed by their local natural enemies into eucalypt communities, particularly in Brazil. Generally there are fewer records relating to local natural enemies and their role in new eucalypt communities. The complexity of new eucalypt communities outside Australia is expected to increase in future.

Highlights

The worldwide expansion of eucalypt forestry has been accompanied by accidental introductions of Australian insect herbivores associated with eucalypts
Australian invaders can be classified into guilds but the relative proportion of native colonizers will be an underestimate for most guilds because there is not sufficient information to assign every native colonizer to a guild. For those native colonizers that could be identified (Figure 4), native leaf chewers, wood borers, termites and sap suckers are more dominant on eucalypts than Australian members of those guilds whereas gall formers are almost exclusively invasive Australian species
There is one reported example where an Australian pest has arrived in a new country (T. peregrinus in Portugal) in association with a new predator, the South American lacewing Hemerobius bolivari (Garcia et al, 2013)

Summary

Introduction

The worldwide expansion of eucalypt forestry (genera Angophora, Corymbia and Eucalyptus, Hui et al, 2014) has been accompanied by accidental introductions of Australian insect herbivores associated with eucalypts. In this contribution the history of eucalypt insect communities that have developed outside Australia is reviewed from the perspective of herbivore guilds, including both the Australian invaders and native colonizers, to compare the relative success of these two groups across different guilds. Irrespective of geographic origin, were grouped into the following feeding guilds: leaf chewers, sap suckers, gall formers, wood borers, termites, and others.

Results

Conclusion