Weeds Down Under: Invasion of the sub-Antarctic wilderness of Macquarie Island

Abstract

The sub-Antarctic islands are some of the least inhabited and most protected ecosystems in the world. Due to their isolation and low human visitation they have escaped the worst effects of alien plant invasion. The sub-Antarctic islands are all nature reserves due to their high conservation values, and Australia's Macquarie and Heard Islands are World Heritage Areas. The sub-Antarctic climate is harsh and the vascular flora is relatively species poor, yet they support a number of endemic species. Despite the isolation of these islands, 108 alien plant species have become established since European discovery, posing threats to their biodiversity. 'Poa annua '(L.) has quickly become widespread throughout the sub-Antarctic since its introduction and is present on all the major island groups. It is widespread on Macquarie Island, readily colonising disturbed areas and competes with native vegetation for space. The highly invasive capabilities of the grass are due to its high phenotypic and genotypic variability, wide tolerance of environmental conditions, and high fecundity. We are investigating the ecology and control of 'P. annua' to broaden understanding of invasion biology and to assist in the development of non-native plant management in the sub-Antarctic and Antarctic region. While previous studies have shown 'P. annua' is a successful weed, in this study we will quantify its traits and growth in the sub- Antarctic. This paper provides a background to the study of 'P. annua' in the sub-Antarctic.