The changing patterns of plant naturalization in Australia

Abstract

Aim: To identify the temporal patterns of plant naturalization in Australia, particularly the interaction between taxonomy, geographic origin and economic use. Location: Australia. Methods: From Australia's Virtual Herbarium, we compiled a database of information for the entire naturalized flora of Australia. We then examined the database in discrete time intervals to determine the changes in patterns of naturalized species taxonomy, geographic origin and economic use over time. Results: Contrary to prevailing hypotheses, we found no evidence to indicate that the rate of alien flora naturalization is increasing in Australia. The number of naturalized species has grown linearly during the period 1880-2000, with the underlying rate of new species detected per thousand specimens declining over the same time period. Despite this, the diversity of both species taxonomy and geographic origin has increased over the last 120 years, leading to increased rates of growth in the total phylogenetic diversity of the Australian flora. Main Conclusions: By classifying species according to their likely origin and economic use, we are able to infer the circumstances driving the patterns of naturalization. In particular, we identify how the contribution of individual pathways has changed since European settlement corresponding with the socio-economic development of the continent. Our study illustrates how the changing nature of 'high-risk' pathways is relevant to directing interventions such as biosecurity regulation.