Dr. Janette A. Steets

Postdoctoral Fellow

Institute of Arctic Biology

University of Alaska Fairbanks

Fairbanks, AK 99775

Office: 248 WRRB

Telephone: (907) 474-5437

E-mail: jsteets at iab.alaska.edu

Education

Ph.D., 2005; Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA.

Dissertation Title: Antagonisms and mixed mating: consequences for the demography of Impatiens capensis.

Advisor: Dr. Tia-Lynn Ashman

B.S., 2000; Department of Biology, Muhlenberg College, Allentown, PA.

Honors Thesis Title: Male-female interactions as a mechanism of nonrandom mating in Mirabilis jalapa.

Advisor: Dr. Richard Niesenbaum

Research Interests

The main thrust of my research is to understand the ecological and genetic forces that control phenotypic diversity and shape adaptive evolution in plants. At a more general level, I am interested in the interplay between ecology and evolution, addressing questions from molecular evolution to population ecology. My research combines observations from wild populations and manipulative experiments, demographic and population projection modeling, and population genetics to gain insights into the selective forces in natural populations and their consequences for population persistence and evolutionary change. Below are a few of my research projects.

I. Adaptation to the Arctic environment

Climate is a powerful selective agent to which plants adapt locally. In the Arctic, plants are faced with extreme climatic conditions, including short, cold growing seasons and low precipitation. For my post-doctoral work with Drs. Naoki Takebayashi and Diana Wolf at the University of Alaska Fairbanks, I am investigating mechanisms for how Arabidopsis lyrata subsp. kamchatica adapts to one aspect of the Arctic climate, low water availability. I have found that the density of trichomes (i.e., leaf hairs) is positively correlated with dryness of habitat. To evaluate whether A. l. kamchatica adapts to local water conditions, I am estimating the magnitude of phenotypic selection on trichome density and physiological traits, including water-use efficiency (quantified using stable isotope signatures and infrared gas analysis), in natural populations that differ in water availability. If A. l. kamchatica adapts to local water conditions, I expect to find divergent selection on these morphological and physiological traits in water-abundant and water-stressed populations.

II. Ecological interactions, mating systems, and population dynamics

As part of my dissertation research at the University of Pittsburgh, I examined the effects of antagonistic interactions for mating system expression of Impatiens capensis. Impatiens capensis produces both obligately selfing (i.e., cleistogamous) and facultatively outcrossing (i.e., chasmogamous) flowers on a single individual, thus, the mating system of this plant is dependent on both the relative production of flower types as well as the selfing rate of the facultatively outcrossing flowers. I found that two of the most prevalent antagonistic interactions faced by plants, vegetative herbivory and intraspecific competition, increase selfing by increasing the proportional production of selfing flowers. Further, I investigated the effects of vegetative herbivory on selfing rate in four natural populations of I. capensis and found that herbivory reduced the selfing rate of the facultatively outcrossing flowers due to changes in flowering phenotype and pollinator visitation and faunal composition. This work demonstrates that interactions between plants and their antagonists affect mating system and further suggests that fluctuations (e.g., spatial or temporal) in the antagonism environment may contribute to the maintenance of mixed mating systems.

I also examined the demographic effects of mixed mating and the consequences of herbivory-induced changes in mating system for I. capensis population dynamics. I found that selfed individuals had higher rates of germination and survival and lower rates of fecundity than did their outcrossed counterparts. In addition, population growth rate was most sensitive to changes in the vital rates of selfed individuals, indicating a large demographic significance of selfing for the populations studied. Herbivory had demographic consequences as this antagonism significantly reduced population growth rate due to its effect on vital rates of selfed individuals. This work is the first to explicitly consider mating system and antagonism-induced changes in mating system in a demographic framework and contributes more generally to our understanding of the relative contribution of genetics and environment in population growth.

Parts of this research were conducted in collaboration with Dr. Tia-Lynn Ashman, Dr. James Hamrick, Dr. Tiffany Knight, and Rhiannon Salla.

III. The ecological and evolutionary causes and consequences of pollen limitation

Pollen sufficiency is an important determinant of plant fitness and thus a major factor influencing plant ecology and evolutionary change. In collaboration with Drs. Tia-Lynn Ashman, Martin Burd, Diane Campbell, Michele Dudash, Mark Johnston, Tiffany Knight, Susan Mazer, Randy Mitchell, Martin Morgan, Jana Vamosi, and Will Wilson, we have recently synthesized hundreds of empirical studies of pollen limitation through a working group at the National Center for Ecological Analysis and Synthesis (NCEAS; funded from 2003-2005). We performed both meta-analysis and phylogenetically-corrected comparative analyses to determine the ecological attributes and plant characteristics that are generally related to pollen limitation. Most recently, we have extended this work to relate pollen limitation to angiosperm species richness. We found a significant positive relationship between pollen limitation and regional species richness, indicating that plants occurring in species-rich communities may be more prone to pollen limitation because of interspecific competition for pollinators.

Publications

Steets, J. A., T. M. Knight, and T.-L. Ashman. Accepted. The interactive effects of vegetative herbivory and mating system for the demography of Impatiens capensis. The American Naturalist.

Knight, T. M., J. A. Steets, and T.-L. Ashman. 2006. A quantitative synthesis of pollen supplementation experiments highlights the contribution of resource reallocation to estimates of pollen limitation. American Journal of Botany 93 (2): 271-277.

Steets, J. A., J. L. Hamrick, and T.-L. Ashman. 2006. The consequences of vegetative herbivory for the maintenance of intermediate outcrossing in an annual plant. Ecology 87(11): 2717-2727.

Steets, J. A., R. Salla, and T.-L. Ashman. 2006. Competition-dependent effects of herbivory for mating system expression in Impatiens capensis. The American Naturalist 167 (4): 591-600.

Vamosi, J. C., T. M. Knight, J. A. Steets, S. J. Mazer, M. Burd, and T.-L. Ashman. 2006. Pollination decays in biodiversity hotspots. Proceedings of the National Academy of Sciences 103(4): 956-961.

Knight, T. M., J. A. Steets, J. Vamosi, M. Burd, D. Campbell, M. Dudash, M. Johnston, S. J. Mazer, R. J. Mitchell, and T.-L. Ashman. 2005. Pollen limitation of plant reproduction: pattern and process. Annual Review of Ecology, Evolution, and Systematics 36: 467-497.

Ashman, T.-L., T. M. Knight, J. A. Steets, P. Amarasekare, M. Burd, D. Campbell, M. Dudash, M. Johnston, S. J. Mazer, R. J. Mitchell, M. T. Morgan, and W. G. Wilson. 2004. Pollen limitation of plant reproduction: ecological and evolutionary causes and consequences. Ecology 85(9): 2408-2421.

Steets, J. A. and T.-L. Ashman. 2004. Herbivory alters the expression of a mixed-mating system. American Journal of Botany 91(7): 1046-1051.