The power of biocontrol for understanding invasions: An analysis of historical and contemporary data

The South American Cactus Moth, Cactoblastis cactorum (Berg) is well-known as a successful biological control species.  After its introduction to Australia by Alan P. Dodd in the 1920s, it quickly eradicated most of the prickly pear cactus that had previously been broadly distributed in Queensland and New South Wales.  Following this (and other) successes, the species has become invasive along the Gulf coast of North America where its western spread poses a threat to both native cactus communities and agriculture in the southwestern US and northern Mexico.  We combine an analysis of A.P. Dodd's rearing notes with data from the native range and invasive populations in North America to demonstrate that any niche shift in this species is the result of ecological displacement that is caused by the different environmental niches occupied by suitable hosts, and not the rapid evolution of exotic populations.  The results of this work demonstrate how biological control species can help to identify the mechanisms that play important roles in the establishment and spread of exotic consumers.