Our research focuses on the population dynamics of plants and how they are influenced by impacts of natural disturbances and global environmental change. We are particularly interested in the interactive effects of fire, grazing and drought in grasslands and woodlands in southern Australia, and how climate change, fragmentation and shrub encroachment affect ecosystems.

Thursday, 19 May 2011

Abundance at 'home' predicts abundance 'away'

One of the best things about teaming up with collaborators, either in your own university, across different institutions, or even across continents, is that it allows you to probe some of the big questions in ecology.

And one of the biggest (and most important) questions that many of us are trying to answer is: why do plants invade new systems? And which species do so? And what are the traits that underpin this?

Recently, I teamed up with a 36-strong global research team that took aim at the reasons for plant invasions in herbaceous ecosystems. Using data collected as part of the Nutnet Project, a research network looking at the importance of top-down and botton-up processes on grassland diversity, we tried to understand why some invaders are common in new habitats, while others are not. Predicting the success of invading species has always relied on the assumption that these plants are more abundant in their new settings than they are in their native communities because they behave in a special way.

Cirsium vulgare - one of the 26 species that
we had data on for the 'home' and 'away' range
(Photo: Royal Botanic Gardens Sydney)
We are not so sure this assumption is correct.

Indeed, we think we have found something pretty cool. Because our study was a global one, we were lucky enough to have data on plant abundance of 26 species in their 'home' range - this allowed us to see which species are common and rare in their natural habitats. For the same 26 species, we had data when they had invaded new habitats (usually grasslands on new continents), which we called the 'away' range.

We discovered two really important things: 1) increases in species abundance in the new range are, in fact, unusual. So, those species that were uncommon in their 'home' range were often uncommon in their 'away' range. 2) We saw quite strong evidence that species common at 'home' were also common 'away' - this might be a really useful way to predict future invader potential.

Hence, success of a plant in its native range can possibly be used to predict its spread at introduced sites – a criterion which currently is not included in biosecurity screening programs.

We've just published this work in Ecology Letters. Check it out.

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