Modeling the natural variation in host quality for an invasive consumer, Cactoblastis cactorum (Berg)

Direct and indirect, trait-mediated effects are important in influencing species interactions, and consequently species’ distributions, dynamics, and persistence. Direct trait-mediated effects may be especially important for specialist consumers whose persistence depends on specific interactions, as well as invasive species that lose, gain, or exchange interactions within an invaded community. The South American cactus moth, Cactoblastis cactorum (Berg), is an invasive specialist whose presence and persistence is directly related to the host species found in the local community. We hypothesize that variation in the macronutrient content of prickly-pear cacti (Opuntia spp., the hosts of C. cactorum) tissues plays an important role in C. cactorum survival and fitness. Here we present the results of field surveys and a series of statistical models that predict the distribution of protein, carbohydrate, lipid, and water concentrations in tissues of natural Opuntia communities. Ultimately, we seek to reconcile these predictive models of regional Opuntia macronutrient concentrations with nutritional performance landscapes for C. cactorum to develop a mechanistic invasion model for this species. Results from this investigation may provide direct insight into identifying Opuntia that may facilitate the future spread of this invasive consumer.