Studies of sensory cues and signals mediating plant-animal interactions have tended to focus only on one scale (community or individual) and one context (attraction). Relatively little is known as to how sensory cues modify behavior across scales and in different contexts. In this study, the tobacco hornworm hawkmoth (Manduca sexta) will be used to address the behavioral roles of relative humidity in foraging choices at different scales (local, habitat and landscape) and contexts (sex, age, nutritional status) and how these interact (additively, synergistically) to modify transitions in nectivorous behaviors of orientation, habitat selection and foraging and their implications for moth fitness. Cross-disciplinary training will be given to atmospheric science undergraduates from Cornell who will not only model relative humidity profiles at the study site, but will come to Arizona to learn, first hand, how climactic variables influence biological processes. This study will also support an outreach program that uses insects to teach biological principals to 2nd grade students in specially designed workshops and classroom visits, reaching over 5000 elementary school students most of whom are minority and of poverty economic status. These students will gain hands-on experience as to the importance of water and humidity in desert environments, how and why insects behave, and that bugs are inherently fascinating. Over 70 Undergraduate Preceptors will be trained in outreach teaching and how to convey an enthusiasm for science to the general public. An outreach program at Cornell ('Insectapalooza') is focused on the extraordinary biology of insects, and will guarantee a strong impact of this project on the public in two diverse cities. The undergraduate students and postdoctoral fellows will receive cross-disciplinary training in ecophysiology, behavior, pollination biology, nutritional ecology and community structure, as well as one-on-one mentoring in experimental design, manuscript writing and the oral presentation of scientific research.
Why don’t animals always respond to stimuli that indicate the presence of food, appropriate habitat or a potential mate? Context-dependence – the impact of an animal’s physiological state, experience, or an external cue that modifies meaning – remains a major hurdle to reaching a nuanced, predictive understanding of behavior, including our own. For example, it has long been known that pest insects, such as locusts or cutworm moths, are indifferent to sex pheromones during migration. This context-dependence of pheromone responses advises to avoid biocontrol strategies (such as pheromone traps) when pest insects are migrating, and suggests alternative control methods, which could exploit, for example, orientation cues used by these insects as they travel long distances. Despite recent breakthroughs in our understanding of insect sensory biology, ranging from identification of the key visual, olfactory and other chemical stimuli that define their sensory world to mapping how nervous systems encode and perceive these stimuli, there remain surprising gaps in our knowledge of how environmental cues (temperature, barometric pressure, relative humidity, atmospheric CO2) modify the perception of such stimuli. We studied the importance of ambient humidity at several spatial scales and in different behavioral contexts, on the orientation, feeding behavior and survivorship of the tobacco hornworm moth (Manduca sexta), a well-studied model insect, and a related, more abundant species, the white lined sphinx moth (Hyles lineata). The Intellectual merits of this project stem neither from novel technological approaches nor from the discovery of hidden genes or neural circuits, but rather from the project’s nested design of exploring the effects of humidity (and the resource it represents – water) at several different scales, and behavioral contexts. Our experiments revealed that humidity is crucial to the moths’ survival – they die sooner and show reduced activity in drier settings – and their feeding preferences, drinking more dilute nectar when they are water stressed, effectively balancing their energetic and osmotic demands. One of our most exciting discoveries was that the night-blooming flowers pollinated by hawkmoths produce transient humidity gradients when they first open, due to the presence of large volumes of nectar within them. We showed that Hyles lineata moths detect and prefer such flowers over those without humidity gradients, and interpret this to mean that they can use such information to find rewarding flowers without having to land or probe within them. In a similar vein, we used behavioral assays to measure how Manduca sexta moths respond to humidity at different scales and contexts. Flying moths consistently oriented towards the more humid air plume in wind tunnel assays, but did not show comparable biases in the context of attractive floral volatiles, or when humidity gradients were established in still air, either at the scale of floral arrays or at a larger (habitat) scale of a greenhouse. These results suggest that moths may respond differently to environmental cues when in flight, especially during long distance dispersal flights between habitats, for which they are famous. The Broader impacts of the project were realized locally at Cornell University, where we had proposed to cross-train a student with a background in atmospheric/earth sciences in behavioral biology. Our hope was to fill an important gap in the way life scientists currently are trained. At present, many organismal biologists are aware of the importance of climate and its volatility, but lack the training necessary to evaluate climatic data. Conversely, few earth scientists have enough training in organismal biology to understand how environmental change will impact living communities. We recruited an earth sciences major, Noah Kaminsky, among seven other undergraduate student researchers, and trained him in all aspects of work on Manduca moths, from maintenance of their lab colony to the design and implementation of behavioral experiments. He presented his work at CURB (http://courses2.cit.cornell.edu/CURB/default.htm), an undergraduate student symposium at Cornell, and since graduation has entered a science education MS program at the American Museum of Natural History. This project involved the training of two postdoctoral researchers (co-PI Joaquin Goyret and postdoc Martin von Arx), two research assistants (Stephanie Topp, Michael Wolfin) and seven additional undergraduates (Kayleigh Sullivan, Margaret Henderson, Trisha Basu, Michael Yuang, Curran Reddy, Karen Chang and Brian Worthington) during this project, all of whom participated in CURB as well as Insectapalooza (http://entomology.cals.cornell.edu/news-events/insectapalooza), an annual open house hosted by Cornell’s Entomology Department, which reaches over 3000 local residents of Tompkins County NY each October. Ms. Sullivan published her project and has begun medical studies at Tufts University, and Mr. Reddy currently works in an exobiology lab at NASA-Ames research center in California. The remaining students will be graduating from Cornell within the next year.
