Modeling realized niches for invasive consumers: a geographic model of resource quality for the South American cactus moth, Cactoblastis cactorum (Berg)

For oligophagous consumers like the South American Cactus Moth, Cactoblastis cactorum (Berg), the indirect effects of climate and weather on resource quality can play a large role in limiting the species’ geographic distribution. Species distribution models based on climatic variables can predict geographic distributions, but they cannot identify the mechanistic links between environment and host quality that may actually govern the consumer’s distribution. Here we develop a series of host quality distribution models (QDMs) for North American Opuntioideae (the hosts of C. cactorum) to predict the geographic distribution of protein, carbohydrate and lipid concentrations for cactus tissues based on site, species, weather, climate, and other environmental factors. Models are compared to the known distribution of C. cactorum in North America to assess the role of each in determining host suitability. The implications for future spread will be discussed. Ultimately, these models will provide the necessary context to develop a series of consumer fitness studies based on host quality that can ultimately be used to develop a mechanistic model of spread for the cactus moth in North America.