PIERRE BINGGELI

 in association with John B. Hall and John R. Healey

AN OVERVIEW OF INVASIVE WOODY PLANTS IN THE TROPICS

TABLE OF CONTENTS

Summary

1 Introduction

2 Overview of invasive woody plants and their comparative analysis
2.1 Introduction
2.2 Background
2.3 Invasive Woody Species Database
2.4 Results and discussion
2.5 Future prospects

3 Invasive woody plants in the tropics
3.1 An historical perspective of the introduction of exotics
3.2 Human perception, ignorance and experience
3.3 Invasive tendencies and species biology
3.4 Time-lags
3.5 Management and policy implications
3.6 Research needs

4 Provisional list of woody plant species invasive in the tropics

5 Case histories of highly invasive woody species in the tropics
5.1 Introduction
5.2 Species description
5.3 Species accounts

6 Acknowledgements

7 Bibliography

School of Agricultural and Forest Sciences Publication Number 13, 
University of Wales, Bangor
1998

SUMMARY

Using databases and associated literature a review of invasive woody plants in the tropics and sub-tropics is presented. It focuses on information not readily available in published overviews on biological invasions.

Using data on 3579 bibliographical references and 653 invasive woody species temporal, spatial, taxonomic and ecological trends and patterns are described. Data for the tropics and sub-tropics are compared to those of the world.

The importance of historical and socio-economic factors in the introduction and subsequent spread of exotic species is examined. The difficulty in identifying the taxonomic nature of an introduced plant, ascertaining whether a plant is native or alien and obtaining historical information is stressed.

Invasive tendencies of woody species and the predictability of a species becoming invasive are reviewed in relation to species characteristics, disturbance regimes and environmental factors. Time-lags between the introductions of tropical woody plants and their spread are investigated in more detail. Published evidence shows that major changes in a biotic factor (e.g. grazing, pollinator, seed disperser) or an abiotic (e.g. fire, wind, flood, logging) factor determines the duration of time-lag.

A list of 235 woody species in tropical and sub-tropical regions is presented with species listed according to life-form and degree of invasiveness. Eighteen species selected from the most highly invasive species category are investigated in greater detail in the form of short species accounts.

1. INTRODUCTION

Biological invasions are considered to be one of the major threats to the earth's biodiversity. Many animal and plant taxa are highly invasive and some species dramatically affect the structure and function of ecosystems. During the 1980s the Scientific Committee on Problems of the Environment (SCOPE) programme attempted to draw attention to this major threat as well and summarize the available information. As a result a large number of books and proceedings were published (e.g. Drake et al. 1989, Duffey 1988, Groves & Di Castri 1991, Ramakrishnan 1991). In the plant kingdom a great number of invasive species are woody. However, a perusal of the SCOPE-related literature indicates that no serious attempt was made at gathering, analyzing and interpreting the available information on woody plant invaders. For example, Rejmáneck (1989) in his review included only 32 woody species. Whitmore (1991) produced a similar review for the tropics, chiefly based on evidence from south-east Asia, and claimed that all tropical moist forests are resistant to invaders although several cases had been previously reported (Binggeli 1990). The books by Cronk & Fuller (1995), Pysek et al. (1995) and Rejmáneck (1996)  provide a much broader, but not comprehensive, review of the subject. 

In this study on woody plant invasions it is intended to:
1.	Provide an overview of the literature and of the main taxonomic, biogeographical and ecological attributes of woody invasive plant species with special reference to the tropics and subtropics (including wet, dry and montane regions). 
2.	Investigate some historical aspects of woody species introductions in the tropics in some detail, 
3.	Raise some key ecological questions such as the existence of time-lags, the reasons for their existence, and whether we can predict events after a potential introduction, 
4.	Produce a provisional list of tropical invasive woody plants, and  
5.	Provide species accounts on a number of highly invasive species and which pay special attention to the autecology of the invaders. An attempt is made to evaluate differences in ecology between the native and invaded ranges in each of these accounts.

Much of the information reported in this study is based on a number of databases on invasive woody plants and associated reprint collection.