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Living on the edge: ecological and evolutionary mechanisms of range expansion in invasive species

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posted on 2022-03-29, 03:30 authored by Samiya Tabassum
Despite ongoing research into traits of successful invasive species, few studies have examined how selection on such traits change during the course of an invasion. This is despite increasing recognition that populations in the invaded range are generally not at equilibrium and many invasive species are still undergoing range expansion. As a species expands in its range from its range core where it was first introduced, populations at the edge of the range may experience different ecological (e.g. fewer enemies) and evolutionary conditions (i.e. selection for increased dispersal, growth and reproduction). Changes in these conditions towards range edges may facilitate continual range expansion and examining how such selective pressures vary across the range of invasive species may increase our understanding of factors determining species' ranges. This thesis explores the ecological and evolutionary mechanisms of range expansion in exotic invasive species using two coastal exotic dune plants (Gladiolus gueinzii Kunze (Iridaceae) and Hydrocotyle bonariensis Lam. (Apiaceae)) occurring along eastern Australia. In particular, it examines variation in enemy attack across ranges (Chapter 2) as well as selection for increased growth (Chapter 3), dispersal (Chapter 4) and reproduction (Chapter 5) towards range edges to facilitate further range expansion. Both H. bonariensis and G. gueinzii did not show consistent responses in terms of enemy release and trait shifts towards range edges. Hydrocotyle bonariensis experienced increased enemy attack and growth towards range edges however there were no such differences towards range edges for G. gueinzii. These inconsistent responses highlight the complexity of understanding factors influencing range expansion within and across species and provide a rich avenue for continued research.


Table of Contents

Chapter 1. Introduction -- Chapter 2. Does enemy damage vary across the range of exotic plant species? Evidence from two coastal dune plant species in eastern Australia -- Chapter 3. Mixed evidence for shifts to faster carbon capture strategies towards range edges of two coastal invasive plants in eastern Australia -- Chapter 4. Have your cake and eat it toov: greater dispersal ability and faster germination towards range edges of an invasive plant species in eastern Australia -- Chapter 5. It doesn't take two to tango : increased capacity for self-fertilisation towards range edges of two coastal invasive plant species in eastern Australia -- Chapter 6. Discussion.


Includes bibliographical references Empirical thesis.

Awarding Institution

Macquarie University

Degree Type

Thesis PhD


PhD, Macquarie University, Faculty of Science and Engineering, Department of Biological Sciences

Department, Centre or School

Department of Biological Sciences

Year of Award


Principal Supervisor

Michelle Leishman


Copyright Samiya Tabassum 2018. Copyright disclaimer:






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