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.


Bronstein, J. L. (1998). The contribution of ant-plant protection studies to our understanding of mutualism. Biotropica, 30(2), 150-161.


One common class of ant-plant mutualism involves ants that defend plants from natural enemies in return for food and sometimes shelter. Studies of these interactions have played a major role in shaping our broad understanding of mutualism. Their central contribution has come via their development of approaches to measuring the benefits, costs, and net outcomes of mutualism, and their explicit consideration of variability in all of these phenomena. Current research on these interactions is suggesting ecological and evolutionary hypotheses that may be applicable to many other forms of mutualism. It is also generating comparative data for testing the few general theories about mutualism that currently exist.

Richardson, L., & Bronstein, J. (2012). Reproductive biology of pointleaf manzanita (Arctostaphylos pungens) and the pollinator-nectar robber spectrum. Journal of Pollination Ecology, 9, 115-123.
Bronstein, J. L. (1988). Mutualism, antagonism, and the fig-pollinator interaction. Ecology, 69(4), 1298-1302.


Examines the role of style lengths in the interaction between the common monoecious Ficus pertusa species and its pollinator Pegoscapus silvestrii (Agaonidae). The author first predicts seed and wasp production from measurements of fig styles and wasp ovipositors, then compares predicted and actual numbers produced. Several other, as yet untested, factors that may limit pollinator fecundity as suggested. The study was conducted in Monteverde, Puntarenas Province, Costa Rica. -from Author

Morris, W. F., Wilson, W. G., Bronstein, J. L., & Ness, J. H. (2005). Environmental forcing and the competitive dynamics of a guild of cactus-tending ant mutualists. Ecology, 86(12), 3190-3199.


In generalized, multispecies mutualisms, competition among members of one guild can influence the net benefits that each species in the other guild receives. Hence seasonal factors that affect the dynamics of competition can also affect net benefits, especially if the benefit or cost of mutualism also varies seasonally. In the Sonoran Desert, two common species of generalist ants compete for access to extrafloral nectaries on the fishhook barrel cactus Ferocactus wislizeni, but their relative abundances vary seasonally; one ant dominates more cacti in winter/spring, and the other in summer/autumn. Recently, a third ant species, which also varies in abundance seasonally, has appeared at our study sites and is competing with resident ants for access to cactus nectaries. This empirical system motivated us to examine a metapopulation model of competition for patches in an open system with periodic forcing. We use the model to: (1) illustrate three ways in which competing species may differ in their sensitivities to environmental conditions that are consistent with seasonally displaced patterns of abundance; (2) ask under what conditions the invasion of a third competitor into a two-species system could alter the sensitivity of the system to environmental forcing at low vs. high frequency; and (3) show how differences among competitors in the pattern of seasonal forcing alone can dramatically alter the outcome of a competitor invasion. We discuss implications of these results for the ways in which seasonal variation among competing mutualists, and the benefits and costs of mutualism, may affect the functioning of generalized, facultative mutualisms. © 2005 by the Ecological Society of America.

Adler, L. S., & Bronstein, J. L. (2004). Attracting antagonists: Does floral nectar increase leaf herbivory?. Ecology, 85(6), 1519-1526.


Traits that are attractive to mutualists may also attract antagonists, resulting in conflicting selection pressures. Here we develop the idea that increased floral nectar production can, in some cases, increase herbivory. In these situations, selection for increased nectar production to attract pollinators may be constrained by a linked cost of herbivore attraction. In support of this hypothesis, we report that experimentally supplementing nectar rewards in Datura stramonium led to increased oviposition by Manduca sexta, a sphingid moth that pollinates flowers, but whose larvae feed on leaf tissue. We speculate that nectar composition may provide information about plant nutritional status or defense that floral visitors could use to make oviposition decisions. Thus, selection by floral visitors and leaf herbivores may be inextricably intertwined, and herbivores may represent a relatively unexplored agent of selection on nectar traits.