Evolution in Spatially-Structured Populations:
Gynodioecy in Silene Vulgaris

Theory suggests that when fitness if frequency-dependent, variance in the local frequency of a trait can be an important component of fitness, but there are few specific examples of this in nature. One example is sex expression in gynodioecious plants where the fitness of both females and hermaphrodites are a function of the frequency of hermaphrodites, so fitness is likely to vary among local populations as the sex ratio varies. We have developed a general model that incorporates spatial structure into the evolution of frequency dependent traits, and have applied it to sex expression in gynodioecious plants. Our work in experimental and in natural populations has shown that the relative fitness of females and hermaphrodites depends on the local frequency of the two sexes. The Silene system therefore represents a clear example of how spatial structure, per se, can influence the outcome of evolution.

This project aims to establish the genetic basis of gynodioecy in Silene vulgaris, and how that varies among populations. For example, we have shown the cytoplasmic male sterility alleles are more structured spatially than are the nuclear restorers. The eventual goal is to combine our crossing studies with molecular phylogenetic analyses of the nuclear and cytoplasmic genomes to elucidate the role of spatial variation in the evolution of sex expression.

Publications - More at Dave McCauley's Page

• Barr, C.M., M. Neiman and D.R. TAYLOR. 2005. Inheritance and recombination of mitochondrial genomes in plants, fungi and animals. New Phytologist 168:39-50.
• Olson, M. McCauley, D. and D.R. TAYLOR.  2005. Genetics and adaptation in structured populations: Sex ratio evolution in Silene vulgaris. Genetica 123:49-62.
• Invgvarsson, P.K. and D.R. Taylor. 2002. Genealogical evidence for epidemics of selfish genes. Proc Nat. Acad. Sci.
• Taylor, D.R., Olson, M., and D. McCauley. 2001. A quantitative genetic analysis of nuclear cytoplasmic male sterility in structured populations of Silene vulgaris. Genetics 158: 833-841.
• McCauley, D. E., Olson, M.S. and D. R. Taylor. 2001 The influence of metapopulation stucture on genotypic fitness in a gynodioecious plant. Evolutionary Ecology 14: 181-194.
• Taylor, D.R., D. McCauley and S. Trimble. 1998. Colonization success of females and hermaphrodites in the gynodioecious plant, Silene vulgaris. Evolution 53: 745-751.
• McCauley, D.E. and D.R. Taylor. 1997. Local population structure and the evolutionary dynamics of cytoplasmic male sterility. American Naturalist 150: 406-419.

Department of Biology, PO Box 400328 University of Virginia, Charlottesville, VA 22904-4328
Email: drt3b@virginia.edu  Phone:(434)982-5217