Alien plant invasions and native plant extinctions: a six-threshold framework

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Bitou bush (Chrysanthemoides monilifera), a South African shrub, has become a significant alien invader in Australia. Bitou bush has been listed a key threatening process under Australian threatened species legislation. Over 150 native plant species have been identified as being threatened from bitou bush invasion. This photo shows bitou bush invading the understorey of Coastal Banksia Woodland in New South Wales, where it threatens numerous native plant species as identified through the NSW Threat Abatement Plan (DEC2006). Photo copyright: Paul Downey
Bitou bush (Chrysanthemoides monilifera), a South African shrub, has become a significant alien invader in Australia. Bitou bush has been listed a key threatening process under Australian threatened species legislation. Over 150 native plant species have been identified as being threatened from bitou bush invasion. This photo shows bitou bush invading the understorey of Coastal Banksia Woodland in New South Wales, where it threatens numerous native plant species as identified through the NSW Threat Abatement Plan (DEC2006). Photo copyright: Paul Downey

Currently there is debate around whether the outcome of alien plant invasions is the extinction of native plants. In a new study published in AoB PLANTS, Downey and Richardson refocus the debate around a series of thresholds along an extinction trajectory where extinction is the end point. They identify and discuss a range of factors that influence our ability to state that extinction has occurred and the role of these factors in determining breaches of the other thresholds along the trajectory. Over-emphasis on the end point of the extinction trajectory ignores strong evidence for declines and breaches of other thresholds along the trajectory which are critical for understanding and managing the threat.

Reference

Paul O. Downey, David M. Richardson, 2016, 'Alien plant invasions and native plant extinctions: a six-threshold framework', AoB Plants, vol. 8, http://dx.doi.org/10.1093/aobpla/plw047


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