When will invasive species be considered native?

Dr Daniel Montesinos is a Senior Research Fellow at JCU, based at the Australian Tropical Herbarium. He said the spread and integration of invasive species into native habitats is unprecedented.

“Biological invasions today are exceptional in that we have no historical records of such a rapid geographic spread of any single species at the same time across every landmass on Earth,” said Dr Montesinos.

He said geographic speciation - the formation of a new and distinct species - happens when biological populations of the same species become isolated due to geographical barriers such as mountains, but also by human introduction into new environments either accidentally or intentionally.

“We expected evolutionary changes to occur over thousands or millions of years. But the time frame we are now looking at for this happening with invasives is less than 200 years,” said Dr Montesinos.

He said invasive populations exposed to climatic niches different from their home ranges can result in rapid local adaptation to the new environments.

“Adaptations commonly involve differences in physiology, size, growth rates and fitness, which result in significant differences in invasive populations from their origin. The evidence we have from some invasive alien species indicates that their transformation into a new species is closer than we expected, it’s now a matter of when not if,” said Dr Montesinos.

He said evidence for invaded communities adapting to invasive species is also mounting.

“One example of this is the coevolution we see between invasive and native plants, in which native plant communities become increasingly tolerant to allelochemicals (protective herbicides) produced by the invasive, which in turn reduce allelochemical production in populations where native plants are tolerant of their presence.

“We also have abundant evidence of invasives integrating into natural interaction networks, for example native bees pollinating introduced weeds,” said Dr Montesinos.

He said for some invasive alien species there is already enough evidence of developing but significant levels of change at the phenotypic, genotypic, and reproductive levels - enough to consider giving them a new name as a new native species.

“The integration of invasives does not lessen their impact in terms of biodiversity loss, extinctions, behavioural changes, disruption of interaction networks, changes in ecosystem functioning and ecosystem services - including changes in nutrient cycling, hydrology, habitat structure, and disturbances.

“These impacts are real and lasting, but so is the naturalisation of numerous non-native species and the need to, at some point, accept them as ‘neo-natives’,” said Dr Montesinos.