A grant has been awarded to Drs. Nancy Moran and Katrina Mangin of the University of Arizona, and Dr. Anthony Ives of the University of Wisconsin to address the role of symbiotic infections in determining tolerance of insects to heat stress, both at the molecular and ecological levels. The complete genome sequence of a facultative bacterial endosymbiont of aphids will be determined. Approaches exploiting this and other genomic data will be used, including measures of expression of heat stress genes of both hosts and symbionts under different thermal environments. These studies will reveal how heat sensitivity is affected by symbiont distributions among hosts as well as by genetic variation in stress responses. In addition, the ecological consequences of variation in thermal tolerances will be examined under field environments; these experiments will reveal how heat tolerance interacts with additional biological factors, such as predators and parasites, to determine population density and persistence.
Chronic infection is a normal part of the life cycle for most animals, including humans and insects, but it is not known how such infection affects tolerance to changing environmental conditions. At the same time, the forces that maintain symbiotic associations are dependent on the joint effects of genetic and environmental factors, but no studies have addressed these together. In this project, researchers with expertise in both ecology and molecular biology will apply methodologies from both fields to obtain answers to these issues. By illuminating the molecular and ecological mechanisms through which heat affects animal populations, the findings will demonstrate how geographic ranges and abundances of individual species are impacted by changes in climate over time. Results will be particularly relevant to insects that are agricultural pests and vectors of disease, a large proportion of which have symbiotic associations similar to those of aphids. In addition, a substantial educational program will introduce Arizona secondary school teachers to the use of state-of-the-art molecular tools for analyzing how organisms interact with environmental stress.
