Research
Ecological and evolutionary physiology of a sphinx moth, Manduca sexta, in North America
 Adults of Manduca quinquemaculata (left) and M. sexta (right) |
 5th instar Manduca sexta on its host plant, Datura wrightii |
 Manduca egg on Datura |
This moth species is distributed widely in North America, with additional subspecies in Central and South America. I'm interested in how a single species can span such different environments—from the Sonoran and Mojave deserts to mesic environments along the East Coast.
Most of my work focuses on the egg stage; I'm interested in other stages too, but don't have time to work on them now.
Specific questions:
- How do eggs solve the oxygen-water tradeoff problem? As non-mobile, non-drinking entities, eggs are laid with all the water they will have until hatching. But they have to spend some of that water to get oxygen. My lab has been studying this tradeoff in detail, focusing on the details of gas exchange across the eggshell. We have also been taking time-lapse movies of embryo development. The movies reveal the developmental timing of important gas-exchange processes. At present we are putting together a system for making movies of 64 eggs developing simultaneously. This high-throughput system will allow us to compare, side by side, eggs developing from different populations or under different controlled environmental conditions.
- How do eggs from different populations solve the oxygen-water tradeoff problem? Different macroenvironmental conditions pose quite divergent gas-exchange problems. My general approach is to understand the relative roles of plasticity and evolution in shaping egg responses. In other words, eggs from different parts of the continent may cope with local conditions by physiological plasticity in developmental timing and gas exchange parameters; or populations may have evolved differences: which is more important and in what contexts? During the summer of 2007 we will be collecting populations from multiple North American locations and establishing lines in the laboratory at UM. Eggs from these populations will be used for detailed examination of eggshell structure and water & oxygen exchange over development.
- What physical conditions do eggs experience in leaf boundary layers? Are boundary conditions less variable on a continent-wide scale than are macro-environmental conditions? Although plant physiologists know a lot about leaf boundary layers, insect biologists have not taken advantage of this knowledge to understand what physical conditions herbivorous insects—across different size scales—experience. We are currently working on methods for measuring the temperatures & humidities experienced by eggs. Eventually we hope to be able to log these conditions across North America, sampling from various host plants that M. sexta uses. These measurements will be integrated into broader theoretical models of boundary layer conditions and will provide the ecological context for understanding population-level differences in egg physiology.
I am currently looking for graduate students interested in working in the framework above. Please contact me if you are interested.