Potential distribution of Opuntia species susceptible to the attack of Cactoblastis cactorum and possible demographic impact on a wild Opuntia population

Background/Question/Methods Population ecology is an important tool for creating managing programs for preventing invasive species. Cactoblastis cactorum (cactus moth) is native to South America, olygophagous on Opuntia. The cactus moth was used for the control of Opuntia in Australia and other countries including some from the Caribbean. Since the introduction of Cactoblastis cactorum in the Caribbean it has moved northward to Florida, and Isla Mujeres, and Isla Contoy in SE Mexico. The presence of the cactus moth in Mexico is of great concern because most Opuntia species have a biological, social or economic importance. We modelled the potential distribution in Mexico of the Opuntia species attacked by the cactus moth and of their morphologically related species using herbarium data and bioclimatic models based on national scale digital cartography. We also modelled the demographic effects of an invasion by C. cactorum on a wild Opuntia population, using Lefkovitch matrix population models. Demographic data was obtained from one wild Opuntia species and the damage by the cactus moth was projected with matrix population models. Perturbations were done on the matrix elements simulating the reduction of demographic processes according to the damage reported by the cactus moth on Opuntia in South Africa

Results/Conclusions The potential distribution of cactus moth partially coincides with the potential distribution of the Opuntia species. The Opuntia species are mainly distributed in the north and center of Mexico, by richness these areas are the most susceptible of damage by the cactus moth attack. Demographically unperturbed Opuntia population showed numerical equilibrium or moderate population increase, while a 10% reduction in plant growth considerably decreased the rate of population increase. Our results suggest that the 58 wild Opuntia species could be seriously affected throughout Mexico by the cactus moth, with important economic social and biological consequences