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Lloyd Stark

Associate Professor
School of Life Sciences
Office: SEB 4170
Phone: 702-895-3119
Fax: 702-895-3956


The primary focus in my lab is an investigation into unbalanced sex ratios in bryophytes with particular attention to sex-specific responses to stress as mediated by the costs of sexual reproduction. Species under study are the cosmopolitan moss Bryum argenteum, the desert moss Syntrichia caninervis, the rare species Pterygoneurum lamellatum, the model organism Physcomitrella patens, and a variety of species in the genera Tortula, Aloina, Funaria and others. Types of stress responses that may be helpful in understanding the female-biased sex ratio that characterizes most bryophyte species include gametophytic and sporophytic desication tolerance (DT), thermotolerance, nutrient stress, microsite disturbance, and overgrowth competition. Current problems under study include the relationship between stress and offspring sex ratios, the cost of inducible vs. constitutive DT systems, plasticity of phenology patterns, sex allocation in mosses, experimental demonstrations of rhizautoicy and self-compatibility in mosses, and the timing of the DT response in both generations of mosses. My graduate students are studying (i) predictive models of species distribution in deserts and (ii) heat shock protein expression during thermal stress.

Desiccation tolerance is the ability of an organism or structure to dry out entirely while retaining viability throughout this dried state. My research focuses on the ecology of tolerating desiccation in the mosses. It includes assessments of constitutive (native) vs. inducible (stimulated) desiccation tolerance, the desiccation tolerance of vegetative and reproductive phases, and phenomena such as hardening and dehardening to desiccation tolerance (becoming increasingly or decreasingly desiccation tolerant). Specifically, my laboratory is investigating how the three components of desiccation tolerance, (i) the rate of drying, (ii) the duration spent in the dried state, and (iii) the equilibrium relative humidity reached, affect the capacity of a species or species structure to tolerate desiccation. We focus on desert mosses.


Ecological Desiccation Tolerance of Bryophytes, Reproductive Biology and Life History of Bryophytes, Desert Bryophytes

Selected Publications

  • Horsley, K., L. R. Stark, and D. N. McLetchie. 2011. Does the silver moss (Bryum argenteum) exhibit gender specificity in growth rate, asexual fitness, or prezygotic reproductive effort? Annals of Botany, in press.
  • Benassi, M., L. R. Stark, J. C. Brinda, D. N. McLetchie, M. Bonine, and B. D. Mishler. 2011. Plant size, sex expression and sexual reproduction along an elevation gradient in a desert moss. Bryologist, in press.
  • Stark, L. R., J. C. Brinda, and D. Nicholas McLetchie. 2011. Effects of increased summer precipitation and N deposition on Mojave Desert populations of the biological crust moss Syntrichia caninervis. Journal of Arid Environments 75: 457-463.
  • Tuba, Z., N. Slack, and L. R. Stark (editors). 2011. Bryophyte Ecology and Climate Change. Cambridge University Press, Cambridge.
  • Cole, D. C., L. R. Stark, M. Bonine, and D. N. McLetchie. 2010. Transplant survivorship of bryophyte soil crusts in the Mojave Desert. Restoration Ecology 18: 198-205.
  • Stark, L. R., D. N. McLetchie, and S. M. Eppley. 2010. Sex ratios and the shy male hypothesis in the moss Bryum argenteum (Bryaceae). Bryologist 113: 788-797.
  • Stark, L. R., J. Brinda, and D. N. McLetchie. 2009. An experimental demonstration of the cost of sex and a potential resource limitation on reproduction in the moss Pterygoneurum (Pottiaceae). American Journal of Botany 96: 1712-1721.
  • Stark, L. R., D. N. McLetchie, and S. P. Roberts. 2009. Gender differences and a new adult eukaryotic record for upper thermotolerance in the desert moss Syntrichia caninervis. Journal of Thermal Biology 34: 131-137.
  • Stark, L. R., M. J. Oliver, B. D. Mishler, and D. N. McLetchie. 2007. Generational differences in response to desiccation stress in the desert moss Tortula inermis. Annals of Botany 99: 53-60.
  • Brinda, J. C., L. R. Stark, J. R. Shevock, and J. R. Spence. 2007. An annotated checklist of the bryophytes of Nevada, with notes on collecting history in the state. Bryologist 110: 673-705.
  • Proctor, M. C. F., M. J. Oliver, A. J. Wood, P. Alpert, L. R. Stark, N. L. Cleavitt, and B. D. Mishler. 2007. Desiccation-tolerance in bryophytes: a review. Bryologist 110: 595-621.

Additional Information

SEB Program Group: Arid Lands Soil-Plant-Water Stress Interactions
SEB Lab Location: 4156
SEB Lab Phone Number: 702-895-4144