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Clarkia xantiana (Onagraceae)

The major focus of research in my lab concerns the evolutionary ecology of reproducton in the California “wildflower” Clarkia xantiana. Studying genetic variation in this species' reproductive traits, at both local and regional scales, has generated several discoveries of broad significance. For example, our recent publications show that sets of reproductive traits (life history, breeding system, flower size) evolve together partly because single traits affect plant performance differently across geographic gradients in precipitation and partly because plant development limits possible trait combinations (Eckhart and Geber 1999; Eckhart, Geber, and McGuire 2004; Geber and Eckhart 2005). We've also learned that the geographic variation in specialist pollinator communites can generate variation in selection on breeding system (Fausto, Eckhart, and Geber 2001), and that specialist pollinators (Eckhart, Rushing, Hart, and Hansen 2006) and generalist herbivores (student projects: Twieg, Hansen, Marsh, Brummel, La Grange, McCord, Hart, Carter) contribute to complex patterns of natural selection on flower color. My students and I are also investigating how transcription regulation of pigmentation genes underlies the ecological consequences and evolutionary dynamics of flower color.

Our newest and most active project--a collaboration with investigators at Cornell University and the University of Minnesota--concerns the ecology and evolution of Clarkia xantiana's geographic range. All species have geographic range limits. Why do these limits occur where they do, rather than elsewhere? Why do some species undergo rapid range expansions, while others remain stable for long periods, and still others contract toward extinction? How is climate warming likely to influence geographic ranges? We are addressing these questions using our study species as a model.

Potential summer MAP students - please click to look at possible range-edge scenarios

Publications | Some Manuscripts on Their Way | Student Projects

  • Eckhart VM, Rushing NS, Hart GM, Hansen JD. 2006. Frequency-dependent pollinator foraging in polymorphic Clarkia xantiana ssp. xantiana populations: implications for flower colour evolution and pollinator interactions. Oikos 112:412-421.
  • Geber MA, Eckhart VM. 2005. Experimental studies of selection and adaptation in Clarkia xantiana (Onagraceae). II. Fitness variation across a subspecies border. Evolution 59:521-531.
  • Eckhart VM, Geber MA, McGuire C. 2004. Experimental studies of selection and adaptation in Clarkia xantiana (Onagraceae). I. Sources of phenotypic variation across a subspecies border. Evolution 58:59-70..
  • Fausto JA Jr, Eckhart VM, Geber MA. 2001. Reproductive assurance and the evolutionary ecology of self-pollination in Clarkia xantiana (Onagraceae). American Journal of Botany 88:1794-1800.
  • Eckhart, V.M., and M.A. Geber. 1999. Character variation and geographic distribution of Clarkia xantiana(Onagraceae): Flowers and phenology distibguish two subspecies. Madrono 46:117-125.
  • Cooper E, Eckhart VM, Watksins SC. Experimental studies of selection and adaptation in Clarkia xantiana (Onagraceae). IV. The genetics of adaptation. in prep.
  • Hart, G.M., and Eckhart, V.M. Ecological separation in diurnal foraging and food type between the major pollinators of Clarkia xantiana ssp. xantiana, in prep.
  • Geber MA, Eckhart VM . Experimental studies of selection and adaptation in Clarkia xantiana (Onagraceae). III. Phenotypic selection across a subspecies border, in prep.
  • Chu, Anna. 2007. Soil compaction and texture controls on the local range limits of Clarkia xantiana ssp. xantiana.
  • Keledjian, Amanda. 2007. Water status of Clarkia xantiana ssp. xantiana: regional versus local controls of species borders.
  • Shannon, Laura. 2006-2007. Gene regulation underlying a flower-color polymorphism in Clarkia xantiana.
  • Louthan, Allison. 2006. Edaphic characteristics and the range limit of Clarkia xantiana ssp. xantiana.
  • Singh, Indrani. 2006. Water relations and the species border of Clarkia xantiana ssp. xantiana.
  • Lundberg, Matthew. 2005. Expression studies of anthocyanin biosynthesis in Clarkia xantiana flowers.
  • Cram, Jacob. 2004. Natural selection on two flower color polymorphisms in Clarkia xantiana ssp. parviflora.
  • Vigeland, Christine. 2004. Development and biochemistry of flower color in Clarkia xantiana.
  • Carter, Daniel. 2003. Petal spots in Clarkia xantiana (Onagraceae) are associated with reduced palatability to grasshoppers.
  • Carter, Daniel. 2003. Analysis of fine-scale spatial variation in the petal spot polymorphism in Clarkia xantiana (Onagraceae): Inbreeding produces finer, more variable structure.
  • Hart, Georgia M. 2003. Sources of variation in pollinator service to Clarkia xantiana (Onagraceae).
  • McCord, Aleia. 2002. Geostatiscal analysis of geographic variation in Clarkia xantiana (Onagraceae).
  • Brummel, Rachel M. 2002. Natural selection on flower color polymorphism in Clarkia xantiana (Onagraceae).
  • Marsh, Naomi. 2002. Opposing forms of frequency-dependent foraging choices in the pollinators of Clarkia xantiana (Onagraceae)
  • Cooper, Elizabeth. 2001. Genetic analysis of breeding system and subspecies differences in Clarkia xantiana(Onagraceae).
  • Fausto, James. 1998-2000. Reproductive assurance and the evolution of autogamy in Clarkia xantiana(Onagraceae).
  • Hansen, Joseph. 1999-2000. The maintenance of a flower-color polymorphism in Clarkia xantiana(Onagraceae). II. Field studies of selection on petal spotting.
  • La Grange, Ceanatha. 1999-2000. The maintenance of a flower-color polymorphism in Clarkia xantiana(Onagraceae). III. Quantitative genetics of petal spotting and herbivore resistance.
  • Southard, Sheryl. 1999. Flowers and stress: Flower size and water relations of Clarkia xantiana(Onagraceae).
  • Lindahl, Amy. 1998-1999. Experimental evidence of a trade-off between stress avoidance and competitive ability in annual plants.
  • Twieg, Elizabeth. 1998. The maintenance of a flower-color polymorphism in Clarkia xantiana(Onagraceae). I. Geographic and subspecies variation in morph frequencies.
  • Watkins, Stephen. 1997, 1998 Developmental basis of self-pollination in Clarkia xantiana(Onagraceae).