3) Phylogenetics — I use phylogenetic analysis of gene sequence data to explore relationships and infer evolutionary history among sexual and apomictic populations of Erigeron. In addition, I employ GIS analyses, using locality data from herbarium specimens, to investigate geographical distributions and ecological correlates of sexual vs. asexual reproduction in nature. My January 2006 NSF proposal to Population Biology is to expand geographical analyses and detail phylogenetic relationships for sexual diploid populations in the complex. Future work will include fine scale geographic mapping in regions of the United States where sexual and apomictic plants are sympatric, as well as investigations of gene flow, reproductive barriers, and ecological parameters in the system.

All of the components of the proposed genetic and phylogeographic work are amenable to undergraduate and graduate students, and I have trained several students to participate in both projects. These projects provide an opportunity to introduce students to a diversity of molecular and analytical techniques and help them explore the conceptual link between genetics and variation in nature.

In essence, 1) meiosis is replaced by mitosis in the formation of unreduced eggs, and, 2) unreduced eggs develop parthenogenetically (without fertilization). Apomixis afflicts many different plant groups, especially in temperate regions, and produces complex (overwhelming?) patterns of variation in nature encompassing both ancestral sexual and derived apomictic populations. Common apomicts include dandelions and many forms of raspberries. The origins of apomixis and the genes that cause the trait are completely unknown.