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Australian Cane Toads: Expanding Their Ranges in Response to Climate Changes
Lindstrom, T., Brown, G.P., Sisson, S.A., Phillips, B.L. and Shine, R. 2013. Rapid shifts in dispersal behavior on an expanding range edge. Proceedings of the National Academy of Sciences USA 110: 13,452-13,456.

The authors write that "dispersal biology at an invasion front differs from that of populations within the range core, because novel evolutionary and ecological processes come into play in the non-equilibrium conditions at expanding range edges."

What was done
Seeking to determine how individual members of a given species disperse at an invasion front, Lindstrom et al. analyzed an extensive dataset they derived from their radio-tracking of invasive cane toads (Rhinella marina) over the first eight years following their arrival at a site in tropical Australia.

What was learned
The five Australian scientists found that "pioneer toads spent longer periods in dispersive mode and displayed longer, more directed movements while they were in dispersive mode." In fact, they discovered that "overall displacement per year was more than twice as far for toads at the invasion front compared with those tracked a few years later at the same site."

What it means
As for what these observations imply, Lindstrom et al. concluded that "studies on established populations (or even those a few years post-establishment) thus may massively underestimate dispersal rates at the leading edge of an expanding population." And they therefore stated that "this, in turn, will cause us to under-predict the rates at which native taxa can expand into newly available habitat under climate change," proffering as an example the fact - as has also been demonstrated by the study of Perkins et al. (2013) - that "previous models of spread rate in toads have underestimated observed spread rates."

Perkins, T.A., Phillips, B.L., Baskett, M.L. and Hastings, A. 2013. Evolution of dispersal and life-history interact to drive accelerating spread of an invasive species. Ecology Letters 16: 1079-1087.

Reviewed 1 January 2014