Thermal physiology and ecology
Neotropical ants (Formicidae) experience a wide range of thermal environments: they forage and nest in diverse microhabitats from above- to below-ground, are active day versus night, and some species span wide elevational ranges. We are exploring how these omnipresent tiny animals respond to their thermal environments by measuring individual, colony, population and species differences in thermal physiology. We are also interested in social thermal homeostasis, especially in army ant bivouacs. After an initial focus on army ants and leaf cutter ants of tropical forests, we are developing new projects on desert seed harvesting ants in Israel.
Brains and the evolution of body shape
Animals range widely in body size, but also vary in shape. Are there fundamental factors that play a strong role in the evolution of animal body structure? We are exploring how brain investment may affect body shape, largely via impacting relative head size.
Neural tissue is among the most expensive to produce and maintain. Recent collaborative work with Alexey Polilov showed that in insects, brains are more strongly hypoallometric than all other major organ systems: small-bodied species have relatively huge brains. We are testing how the need to house brains may constrain the evolution of animal shape via relative head volume and anterior/posterior weight distributions.
Neuroecology: Evolution of brain architecture in social insects
Paper wasp species vary in colony size, mode of colony founding, nest architecture, and in the degree of queen-worker caste differentiation. We are exploring how species differences in behavior and development, such as nest architecture and caste determination, have affected the evolution of the amount of investment in functionally distinct brain regions. The family Vespidae ranges from solitary species, through species with small simple societies, to those with large and complex colonies. We are quantifying how the evolution of social behavior affected brain investment, leading to developing new theory on brain/behavior relationships in the form of adjustments to the social brain hypothesis. Much of this work has focused on paper wasps, but we are making parallel inquiries using social spiders.
Brain development and plasticity: Individual and caste differences in brain architecture
The main goal of this project is to assess whether neural plasticity in the brain, particularly in the mushroom bodies, plays a functional role in social insect workers' task performance. After initial work on paper wasps we recently began work on caste-flexible dampwood termites and social desert isopods. We use microscopy techniques to measure the volumes of functionally distinct regions of individual's brains. We test whether the size of different brain regions corresponds to individual differences in age, social rank or caste, and task performance. We used Golgi staining methods to quantify changes in dendritic processes of brain neurons that may underlie changes in neuropil volume.
Division of labor and behavioral physiology in social insects
Social dominance is often based on aggressive interactions that influence individuals' access to resources. Dominance among female social wasps plays a role in governing the separation between reproductive roles (queen castes) and sterile, helping roles (worker castes). My lab has worked on independent-founding (Polistes and Mischocyttarus) and swarm-founding (Polybia) social wasps to assess how interactions within the worker force influence task performance and non-reproductive division of labor (polyethism). We are particularly interested in the role of adult nutrition in governing social roles. We used stable isotope analyses to test for behavior-related nutritional (trophic level) differences among colony mates.
Competition and facilitation among foragers: Bird/army ant interactions
A diverse fauna of birds attends army ant raids in montane tropical forests. The birds obtain food at the swarm raids by capturing small animals that flee the advancing army ants. The montane attendants are particularly interesting because few or no true antbirds (Thamnophilidae) are present in montane forests; we are exploring the possibility that high-fidelity specialized ant following behavior has evolved convergently in some montane bird species. Raid attending birds provide a good system for exploring the balance of inter-species competition with facilitation and information sharing.
Some birds that specialize as army ant followers engage in elaborate behavior called bivouac checking. These birds visit the temporary resting clusters of a series of army ant colonies in the early morning, apparently assessing the ant's raid activity for that day. We are interested in the cognitive implications and challenges of bivouac checking for the birds.
Developing a non-nutritive sweetener as a human-safe insecticide
We found the sweet polyalcohol erythritol is effective as an insecticide when ingested by insects. Starting with lab fruit flies, the work has expanded to testing on other insects (several species of ants, mosquitoes, termites and field tests on berry crop pests). We hold a provisional US patent for use of erythritol in insect control. We are excited about the potential for contributing new safer methods of insect control in a range of systems and contexts.