Jason Pienaar

Jason  Pienaar

Assistant Professor


  • Ph.D., Genetics, University of Pretoria, South Africa, 2005
  • Postdoctoral research: Florida State University, the University of Florida, the University of Hawaii, and the University of Gothenburg, Sweden

Research Interests

My research interests span different levels of phenotypic evolution. Mainly I develop game theoretical models to predict optimal sex allocation in patch-structured populations, phylogenetic comparative methods to test the generality of adaptive evolutionary processes and I dabble with Tardigrades.

Sex allocation and other maternal effects in patch structured populations.
Fig wasps are phenomenal – their ability to adjust sex allocation under conditions that select for a range of biased sex ratios result in an almost perfect model organism for quantitatively testing the precision of adaptation. A wide range of models that predict sex allocation strategies based on various assumptions of the evolutionary process can be tested with simple count data obtained from fig wasp populations.

Phylogenetic comparative methods for adaptive evolution.
Most phylogenetic comparative methods are geared towards correcting potential pseudo-replication that comes about through phylogenetic relatedness. Thus trait values for different species in the same selective environment may be similar because they exhibit a general adaptive solution or because they inherited the trait from a common ancestor without subsequent change. Using the latter case as evidence for the former is often assumed to be akin to using numerous eyewitness accounts of an event from the same eyewitness as repeated, reliable evidence.  A widely used solution is to simply ignore / correct for the portion of trait values that are similar and focus only on testing whether traits differ in different selective environments, but this approach ignores the possibility of maintenance of species trait values under stabilizing selection. Our goal here is to develop macroevolutionary methods that are consistent with the theoretical frameworks (optimality, population and quantitative genetics) used to understand the microevolutionary process.

Tardigrades are terrific. I have recently started a project to develop these organisms into a model comparative system for studying trait adaptation across species.

Selected Publications

Pienaar, J., Ilany, A., Geffen E.,  & Yom-Tov, Y.  2013. Macroevolution of life history traits in passerine birds: adaptation and phylogenetic inertia. Ecology Letters 16: 571-576.

Davis, R. B., Javois, J., Pienaar, J., Ounap, E. & Tammaru, T. 2012. Disentangling determinants of egg size using an advanced phylogenetic comparative method: Maternal body size is the primary factor in geometrid moths. Journal of Evolutionary Biology 25: 210-212.

Bartozek, K, Pienaar, J., Hansen, T.F. & Mosstad, P. 2012. A multivariate comparative method for studying adaptive optimality.  Journal of Theoretical Biology 314: 204-215.

Uyeda, J. C., Hansen, T. F., Arnold, S. J. & Pienaar, J.  2011. The million year wait for macro evolutionary bursts.  Proceedings of the National Academy of Sciences 108: 15908-15913.

Wayne, M. L., Pienaar, J., Telonis-Scott, M., Sylvestre, L-S, Nuhzdin, S., V. & McIntyre, L. M. 2011. Expression of defense genes in Drosophila evolves under a different selective regime from expression of other genes. Evolution 65: 1068-1078.

Labra, A., Pienaar, J. & Hansen, T. F. 2009. Evolution of thermal physiology in liolaemus lizards: adaptation, phylogenetic inertia and niche tracking. The American Naturalist 174: 204-220.

Hansen, T. F., Pienaar, J. & Orzack, S. H. 2008. A comparative method for studying adaptation to a randomly evolving environment. Evolution 62: 1965-1977.

Pienaar, J. & Greeff, J. M. 2006. Adaptive non-Fisherian sex ratios in a patchily distributed population with outbreeding. Evolutionary Ecology 20: 431-445.

Moore, J. C., Pienaar, J. & Greeff, J. M.  2004 Male morphological variation and the determinants of body size in two Otitesella fig wasps.  Behavioral Ecology 15 735-741.

Pienaar, J. & Greeff, J. M. 2003. Maternal control of offspring sex and male morphology in the Otitesella fig wasps. Journal of Evolutionary Biology 16: 244-253.

Pienaar, J. & Greeff, J. M. 2003. Male dimorphic Otitesella fig wasps have equal fitness but are not genetically discrete. Ecology Letters 6: 286-289.