My research interests are dominated by the physiological basis of caste differences in social insects, especially ants. Why ants? Some think it may have been early determination. I am especially interested in the relevance of physiology to both social organization and evolution of insect sociality. My research has included included regulation of oogenesis, storage of proteins by adult workers and queens, mechanisms of sperm storage by queens, and, of course, caste determination.
Caste determination: We are working on the molecular basis of caste determination in honey bees. Since caste is determined by the diet larvae receive, caste determination involves signaling pathways that are fundamental to pathways regulated by nutrition in all organisms, even single-celled ones. Insulin and TOR signaling pathways are turning out to be especially important. We are also working to understand how pathways are shaped by natural selection acting at the level of the colony, in addition to at the level of the individual. Our partner in this project is Jay Evans and the USDA Bee Research Lab in Maryland. We are also collaborating with Gloria DeGrandi-Hoffman at the USDA Bee Research Lab in Tucson.
Role of endosymbionts in the biology of Camponotus ants: Molecular methods have opened up the world of unculturable bacteria for us. The presence of endosymbionts in Camponotus has been known for decades but only now are we able to explore the functional relationship between Blochmannia bacteria and their ant hosts. We are working to understand the dynamic interactions between the partners, through development, in different castes and in different ecological contexts. Our research partner in this work is Jennifer Wernegreen at the Josephine Bay Paul Center at Woods Hole. I also have a long standing interest in the relationship between cephalotine ants and their gut symbionts.
Storage proteins: Storage proteins serve insects as a bank for amino acid and nitrogen reserves. The importance of storage proteins was first understood in the context of metamorphosis. Members of my lab have shown that storage proteins play many roles in adult insects as a resource for : claustral colony founding in ants, seasonal storage in ants, colony founding in termites, autogenous egg production in mosquitoes, and egg production in Lepidoptera. As universal indicators of nutritional state, storage proteins are turning out to be important aspects of our research on both caste determination in honey bees and endosymbiont interactions in Camponotus.
Ming Huang is a Ph.D. student interested in ecology and caste in Pheidole ants. Several local species have highly unusual soldier castes showing a wide range of soldier sizes. He is interested in the development of worker caste demography during colony ontogeny and in the ecological significance of super soldiers.
Kirk Anderson is a post-doctoral researcher studying genetic and environmental systems of queen determination in Pogonomyrmex ants.
Norm Buck is research specialist with extensive experience with biochemical, molecular, and programming tools important in probing numerous aspects of insect biology.
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When we started our project on the molecular basis of caste determination in honey bees, the honey bee genome sequencing project had not even begun. Its progress, then its completion, allowed us to take a huge leap forward and see if insulin signaling is involved in the response of future queen and worker larvae to their radically different diets. And the answer is... yes it is!
Here we go over what is known so far about how gene expression results in polyphenisms. The best part is that we look ahead to the new age of research on caste determination and develop some focal questions.
I did this work in Germany while on sabbatical. We were startled to find that the egg protein of some ponerines has a structure similar to that of sawflies instead of other ants and higher Hymenoptera. Go figure.
This is a really neat study showing the dynamics of females and males during a mating flight AND the paternity of the offspring.
I wrote this review as an attempt to compare social insects with other insects, so there is a social insect section. The review points out some neat unstudied questions in Lepidoptera also.
This paper is a review and summary of all our work on the character and function of storage proteins in ants.
This was our first paper showing that storage proteins (hexamerins) are involved in claustral colony founding by queens and are accumulated by workers in the absence of brood. Therefore, adult ants have co-opted this typically larval specific protein for caste-specific functions
This was our first research addressing mechanisms of egg development and its inhibition. Since regulation of female reproduction is the 'cornerstone' of insect sociality, I wanted to investigate how the insects did it. The results demonstrate that workers build up high vitellogenin titers in the blood and that social factors are important in determining these.
This was a synthesis of everything I knew about mechanisms generating worker castes in ants. Could these mechanisms produce the spectacular caste systems seen in ants like Eciton? Looks like it. If I could revise the paper today, I would include a discussion of non-cue based systems and de-emphasize negative feedback.
In this paper, I synthesized all the information available at the time to put processes of caste determination in social Hymenoptera into a single framework. In the past ten years, the area to which the most information has been added is caste and reproductive differentiation in wasps.
Graduate Interdisciplinary Program in Insect Science
Department of Entomology
The University of Arizona