Research Interests


My research focuses on the ecology and management of diversity and distributions, particularly relating to biological invasions. The image below is a word cloud constructed in Wordle from the titles of my publications and conference presentations since 2005. It neatly summarizes my recent research activity.

Most of my recent research falls into one or more of the categories to follow.

Trees and shrubs as invasive species - understanding invasion dynamics & forging management strategies in a changing world

Woody plants were not widely considered to be important invasive alien species until fairly recently. Thousands of species of trees and shrubs have, however, been moved around the world. Many species have spread from planting sites, and some are now among the most widespread and damaging of invasive organisms [read a recent global review and the 2013 update of the database].

Pines (genus Pinus) and other conifers have featured prominently in my research on the dynamics of plant invasions. Because of the large number of species in the genus Pinus (about 111), the wide range of ecological adaptations in different species, and because many species have been so widely planted in many habitats outside their natural range, studies on pine invasions have been useful for shedding light on many aspects of plant invasion ecology. Recent research in my lab on pines as invasive species has focussed on understanding macroecological patterns, and providing guidelines for strategic management of pine invasions in the southern hemisphere.

Australian acacias or “wattles” (1012 recognized species native to Australia, previously grouped in Acacia subgenus Phyllodineae) are currently a strong focus of my research. Many species have been moved around the world by humans over the past 250 years. This has created the opportunity to explore how evolutionary, ecological, historical and sociological factors interact to affect the distribution, usage, invasiveness and perceptions of a globally important group of plants. Recent research on Australian acacias by my group has dealt with:

Other work on particular invasive tree species or genera has dealt with the invasion ecology of Brazilian peppertree (Schinus molle) and the ecology of Eucalyptus trees as introduced species around the world. Several studies have addressed the invasion ecology of Eucalyptus camaldulensis along rivers of the Western Cape. My group is currently also working on aspects of the invasion ecology of “brooms” (25 genera in the tribe Genisteae, Fabaceae), Casuarina, Lantana camara, dry-seeded species of Myrtaceae, Proteaceae, and Prosopis in South Africa.

South Africa’s fynbos biome has been severely invaded by non-native tree species. The management of invasive trees is one of the most taxing challenges facing conservation managers in this region. Substantial research effort has been and will continue to be devoted to exploring the complexity inherent in managing invasive woody plants in the fynbos. This work involves a range of modelling approaches, scenario planning, and other methods aimed at providing guidelines for more effective management.

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Mutualisms - key drivers of invasions.... key casualties of invasions

Symbiotic relationships between plants and other organisms are crucial mediators of invasion success for introduced plants. Seed dispersal and pollination by animal agents and relationships between plants and micro organisms in the soil often determine whether a species will invade and/or the extent to which it will spread in a new environment. Many non-native plant species become invasive by infiltrating pollination or seed dispersal networks. Biological invasions also have a profound effect on naturally occurring mutualisms. Some such impacts are widely known, but the mechanisms that produce such impacts are poorly understood. Many types of invasive species have huge potential to alter evolutionary trajectories by causing many types of changes to prevailing mutualisms. This introduces a new layer of complexity to programmes aiming to reduce or mitigate the effects of biological invasions.

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Invasion ecology - firming up the game rules

Invasion ecology is the study of the human-mediated introductions of organisms, especially to areas well outside their potential range as defined by their natural dispersal mechanisms and biogeographic barriers. The field covers all aspects relating to the introduction of organisms, their capacity to naturalize and invade in the target region, their interactions with resident biota and, increasingly, the consideration of costs and benefits of their presence and abundance with reference to human value systems. Interest in biological invasions has grown exponentially in the past two decades. I have a special interest in contributing to the development of clear and objective concepts in invasion ecology, particularly relating to plant invasions. Contributions in this area in recent years have included the following:

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Practical biogeography: approaches for sustainable conservation in the Anthropocene

The increasing human domination of the world is forcing us to revisit key tenets of paradigms relating to conservation of biodiversity. Biological invasions are interacting with numerous other human-mediated drivers to bring about radical changes to ecosystems worldwide. Such changes provide numerous challenges for conservationists and resource managers. I am very interested in contributing to the development of novel approaches for sustainable ecosystem management in our rapidly changing world. To this end, I have been involved in the following initiatives:

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