Abstract

For a plant species to become invasive it has to progress along the introduction-naturalization-invasion (INI) continuum which reflects the joint direction of niche breadth. Identification of traits that correlate with and drive species invasiveness along the continuum is a major focus of invasion biology. If invasiveness is underlain by heritable traits, and if such traits are phylogenetically conserved, then we would expect non-native species with different introduction status (i.e. position along the INI continuum) to show phylogenetic signal. This study uses two clades that contain a large number of invasive tree species from the genera Acacia and Eucalyptus to test whether geographic distribution and a novel phylogenetic conservation method can predict which species have been introduced, became naturalized, and invasive. Our results suggest that no underlying phylogenetic signal underlie the introduction status for both groups of trees, except for introduced acacias. The more invasive acacia clade contains invasive species that have smoother geographic distributions and are more marginal in the phylogenetic network. The less invasive eucalyptus group contains invasive species that are more clustered geographically, more centrally located in the phylogenetic network and have phylogenetic distances between invasive and non-invasive species that are trending toward the mean pairwise distance. This suggests that highly invasive groups may be identified because they have invasive species with smoother and faster expanding native distributions and are located more to the edges of phylogenetic networks than less invasive groups.

Highlights

  • In order to anticipate which introduced species might become invasive it is crucial to identify those characteristics that are correlated with, and potentially drive, species overcoming the so-called introduction-naturalization-invasion (INI) continuum (Blackburn et al 2011; Richardson and Pysek 2012; Hui et al 2013)

  • Visual inspection does not identify specific clades that are highly represented by introduction status in either the acacia or eucalypt phylogenies

  • There is no indication of clustering of any of the naturalized or invasive comparisons in Acacia when compared with a tree that does not contain non-introduced species

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Summary

Introduction

In order to anticipate which introduced species might become invasive it is crucial to identify those characteristics that are correlated with, and potentially drive, species overcoming the so-called introduction-naturalization-invasion (INI) continuum (Blackburn et al 2011; Richardson and Pysek 2012; Hui et al 2013). The continent has been drifting away from other large landmasses for 50 million years, which has limited dispersal to and from Australia (Crisp and Cook 2013) This has led to the evolution of large and unique flora, such as wattles (genus Acacia), eucalypts (genera Angophora, Corymbia and Eucalyptus) and several lineages of the Proteaceae such as members of the Banksia and the Grevillea/Hakea clades, that are wholly, or almost exclusively, native to the continent. These lineages evolved during large-scale environmental fluctuations that fostered their diversifications, notably during relatively recent periods of aridification (over the last 8–10 million years; Byrne et al 2008)

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