Stephen M. Shuster


Phone: 928-523-9302
Office: Bldg. 21 Room 302

Research/teaching interests: 


  • animal and plant mating systems
  • male and female reproductive strategies
  • evolution and population structure in marine organisms
    • animal mating systems

    Academic highlights

    • PhD: Department of Zoology, University of California, Berkeley, 1987
    • MS  Department of Biology, University of New Mexico, Albuquerque, 1979 
    • BS Department of Zoology, University of Michigan, Ann Arbor, 1976

    My fundamental research goals are to understand (1) the processes by which genetic variation is maintained in natural populations, (2) the genetic and environmental bases for the expression of sexual phenotype, (3) how selection can be measured in nature, and (4) how mating systems and alternative mating strategies evolve.

    My research and scholarship efforts at Northern Arizona University have developed in several major directions, which are extensions of these goals:

    Alternative Mating Strategies: My primary research involves investigation of expression of adult phenotype and population sex ratio in marine isopods, Paracerceis sculpta. This project is an extension of my dissertation research and was continuously supported by NSF for nearly 25 years. The goal of this project is to understand the genetic and environmental mechanisms that maintain phenotypic variability in natural populations, and that allow alternative male mating strategies to persist in nature. In future years, I plan to specifically investigate variation in the genetic factors that cause sex ratio biases in the natural population, as well as explore the effects of climate change and predation on the character of breeding aggregations. 

    Mating System Evolution: Another project involves my continuing collaboration with Michael J. Wade at Indiana University. We are extending the theoretical principles developed in our book entitled "Mating Systems and Strategies" published by Princeton University Press in 2003, to include both plant and animal mating systems. This book outlines a novel statistical approach for measuring the intensities of natural and sexual selection in nature. This approach provides new insights into why sexual selection is such a powerful evolutionary force, and it provides unique explanations for observed variation in mating systems and alternative mating strategies for all sexually reproducing organisms.

    Community Genetics: I am also involved in community genetics research in collaboration with the Cottonwood Ecology Group at NAU. As part of this project I am interested in exploring methods for estimating the intensity and form of genetic interactions within and among species from individual to ecosystem scales, particularly using invertebrate animals. I am also interested in exploring statistical approaches for estimating how and to what degree individuals, species and communities may become genetically and phenotypically distinct.

    Invertebrate Zoology: I am broadly interested in the evolutionary biology of invertebrate animals and have expanded this interest into a co-authored textbook entitled Invertebrates, 3rd Ed., published in 2016 by Sinauer Associates (now Oxford University Press) with Richard C. Brusca of the Sonora Desert Museum and Wendy Moore of the University of Arizona. This book provides the most comprehensive and up to date treatment of invertebrate biology and evolution now available.

    Recent postdoctoral associates in my laboratory have investigated (1) the relative influences of social and sexual selection via indirect genetic effects (IGEs) on the evolution of cannibalistic behavior and body size, isopod crustaceans, (2) genetic interactions influencing the expression of parental care in sea spiders, leeches and syngnathid fish, and (3) estimates of community heritability and interspecific indirect genetic effects (IIGEs) for arthropod communities inhabiting cottonwood trees. 

    Selected publications 

    Brusca, R. C., W. Moore, and S. M. Shuster. 2016. Invertebrates, 3rd ed. Sinauer Associates, Sunderland MA. 1105 pp.

    Shuster, S. M. 2016. Operational Sex Ratio (OSR). Encyclopedia of Evolutionary Biology, R. Kliman, N. Wedell, eds. vol. 3, pp. 167–174. Oxford: Academic Press.

    Hultine, K. R., K. C. Grady, T. E. Wood, S. M. Shuster, J. C. Stella, T. G. Whitham. 2016. Climate change perils for dioecious plant species. Nature Plants DOI: 10.1038/NPLANTS.2016.109.

    Prather, R. B. and S. M. Shuster. 2015. The opportunity for post-copulatory sexual selection in the ectoparasitic pea crab, Dissodactylus primitivus. PLOSOne DOI: 10.1371/journal.pone.0145681.

    Shuster, S. M., W. R. Briggs and P. A. Dennis. 2013. How multiple mating by females affects sexual selection. Philosophical Transactions of the Royal Society B 368 (1613): 20120046.

    Shuster, S. M. 2009. Sexual selection and mating systems. Proceedings of the National Academy of Sciences 106: 10009-10016.

    Whitham, T. G., S. P. DeFazio, J. A. Schweitzer, S. M. Shuster, G. J. Allen, J. K. Bailey, S. A. Woolbright. 2008. Extending genomics to natural communities and ecosystems. Science 320: 492-495.

    Shuster, S. M. and M. J. Wade. 2003.Mating Systems and Strategies. Princeton University Press, Princeton, NJ