Judith Bronstein
Professor, BIO5 Institute
Professor, Ecology and Evolutionary Biology
Professor, Entomology / Insect Science - GIDP
University Distinguished Professor
Primary Department
(520) 621-3534
Research Interest
Judith L. Bronstein is University Distinguished Professor of Ecology and Evolutionary Biology, with a joint appointment in the Department of Entomology. Dr. Bronstein’s large, active lab focuses on the ecology and evolution of interspecific interactions, particularly on the poorly-understood, mutually beneficial ones (mutualisms). Using a combination of field observations, experiments, and theory, they are examining how population processes, abiotic conditions, and the community context determine net effects of interactions for the fitness of each participant species. Specific conceptual areas of interest include: (i) conflicts of interest between mutualists and their consequences for the maintenance of beneficial outcomes; (ii) the causes and consequences of "cheating" within mutualism; (iii) context-dependent outcomes in both mutualisms and antagonisms; and (iv) anthropogenic threats to mutualisms. In addition, she is Editor-in-Chief of The American Naturalist, a leading international journal in ecology and evolution. An award-winning instructor, Dr. Bronstein teaches at both the undergraduate and graduate levels; she has also run a large training grant administered by BIO5 that places life sciences graduate students in public school classrooms around Tucson. She serves in leadership positions in the College of Science (including chairing the College of Science Promotion and Tenure Committee for 2013), at the University, and at the Arizona-Sonora Desert Museum, where she is a member of the Board of Trustees and Chair of the Science and Conservation Council.


Boyle, W., Conway, C., & Bronstein, J. (2011). Why do some, but not all, tropical birds migrate? A comparative study of diet breadth and fruit preference. Evolutionary Ecology, 25, 219-236.
Bronstein, J. L., & Hossaert-McKey, M. (1996). Variation in reproductive success within a subtropical fig/pollinator mutualism. Journal of Biogeography, 23(4), 433-446.


Plants pollinated by specialists are often thought to receive exceptionally high-quality pollinator service, but in relatively low and unpredictable quantities. We examine and reject this hypothesis for an obligate mutualism between a subtropical New World fig (Ficus aurea) and its species-specific pollinator (Pegoscapus jimenezi). Fig wasps lay eggs within the flowers they pollinate; their offspring destroy a large proportion of fig's seeds. In a 6-year study of this interaction in Florida, U.S.A., we found that pollination intensity was in fact relatively high. Also contrary to expectations, reproductive success of both mutualists (as well as other wasps cohabiting the figs) was extremely variable and generally low, at three different scales of sampling: among figs from a single crop of one tree (thirty-four figs), among crops produced at different times by that tree (126 figs), and across trees over a 1-year period (379 figs). Although variable, fig contents were not completely unpredictable. For example, seed and wasp numbers increased with the number of flowers in a fig, and female and male flower numbers increased together. Little is yet known about the causes either of these relationships or of the massive fig-to-fig variation itself, although there is some evidence that they exist in other fig species as well. Further investigations of these patterns should shed new light on the ecology and evolution of this mutualism.

Contreras, H. L., Goyret, J., Arx, M. v., Pierce, C. T., Bronstein, J. L., Raguso, R. A., & Davidowitz, G. (2013). The effect of ambient humidity on the foraging behavior of the hawkmoth Manduca sexta. Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology, 199(11), 1053-1063.

PMID: 23756587;Abstract:

The foraging decisions of flower-visiting animals are contingent upon the need of an individual to meet both energetic and osmotic demands. Insects can alter their food preferences to prioritize one need over the other, depending on environmental conditions. In this study, preferences in nectar sugar concentrations (0, 12, 24 %) were tested in the hawkmoth Manduca sexta, in response to different levels of ambient humidity (20, 40, 60, and 80 % RH). Moths altered their foraging behavior when placed in low humidity environments by increasing the volume of nectar imbibed and by consuming more dilute nectar. When placed in high humidity environments the total volume imbibed decreased, because moths consumed less from dilute nectars (water and 12 % sucrose). Survivorship was higher with higher humidity. Daily foraging patterns changed with relative humidity (RH): moths maximized their nectar consumption earlier, at lower humidities. Although ambient humidity had an impact on foraging activity, activity levels and nectar preferences, total energy intake was not affected. These results show that foraging decisions made by M. sexta kept under different ambient RH levels allow individuals to meet their osmotic demands while maintaining a constant energy input. © 2013 Springer-Verlag Berlin Heidelberg.

Bronstein, J. L., Armbruster, W. S., & Thompson, J. N. (2014). Understanding evolution and the complexity of species interactions using orchids as a model system. New Phytologist, 202(2), 373-375.
Holland, J. N., DeAngelis, D. L., & Bronstein, J. L. (2002). Population dynamics and mutualism: Functional responses of benefits and costs. American Naturalist, 159(3), 231-244.

PMID: 18707376;Abstract:

We develop an approach for studying population dynamics resulting from mutualism by employing functional responses based on density-dependent benefits and costs. These functional responses express how the population growth rate of a mutualist is modified by the density of its partner. We present several possible dependencies of gross benefits and costs, and hence net effects, to a mutualist as functions of the density of its partner. Net effects to mutualists are likely a monotonically saturating or unimodal function of the density of their partner. We show that fundamental differences in the growth, limitation, and dynamics of a population can occur when net effects to that population change linearly, unimodally, or in a saturating fashion. We use the mutualism between senita cactus and its pollinating seed-eating moth as an example to show the influence of different benefit and cost functional responses on population dynamics and stability of mutualisms. We investigated two mechanisms that may alter this mutualism's functional responses: distribution of eggs among flowers and fruit abortion. Differences in how benefits and costs vary with density can alter the stability of this mutualism. In particular, fruit abortion may allow for a stable equilibrium where none could otherwise exist.