A century of data suggests a key role for biological interactions in the global spread of the South American cactus moth, Cactoblastis cactorum (Berg)

The global spread of the South American cactus moth, Cactoblastis cactorum, has been very well documented.  All of the populations outside the native range are derived from a set of collections made in 1925 from a single ecotype of the moth along the Argentine-Uruguayan border. These data provide a unique opportunity to evaluate the role of biological interactions on invasion success. Environmental niche models based on locations in the native range suggest that biological interactions have constrained invasion success in North America. I will present data on the biological interactions along the stable northern limit of the moth in the USA and discuss the influence of host physiology and competition in establishing this limit. In addition, I will discuss the distribution of hosts and potential new associations with cactus-associated insects that will influence further westward spread of the moth along the gulf coast. Data will be evaluated in the context of historical data collected from lab notebooks and reports of early work in the Americas and subsequent introduction of the moth into Australia. Together, the data suggest a central role for biological interactions in the past, present and future spread of this invasive insect.