Paul G. Wolf

Utah State University

The main focus of my lab is using molecular data to address questions of pteridophyte and vascular plant evolution. For the past three years I have collaborated with Kathleen Pryer (Field Museum, Chicago) and Alan Smith (University of California, Berkeley) to generate and compile a dataset of over one hundred morphological characters and nucleotide sequences for four genes for representatives of all major extant groups of vascular plants. Our findings provide good evidence that the ferns and horsetails together form a clade that is sister to the seed plants, and that the whisk ferns (Psilotum and Tmesipteris) are sister to the eusporangiate ferns (Ophioglossaceae). Several of our results imply relationships that differ from earlier ideas and may require reassessments of our understanding of morphological, developmental, and reproductive evolution in the vascular plants. Our results also show the utility of a large and diverse dataset for addressing phylogeny, in cases where single-gene data have given poor resolution or conflicting results. However, many of the divergence relationships we seek to identify are ancient (over three hundred million years) so it is still necessary to test our results with independent data. To this end I have initiated a pteridophyte chloroplast genome sequencing project. The complete chloroplast genomes of several seed plants have been sequenced previously, as well as several "green algae" and a liverwort. However, the only representative of the basal vascular plants is the recently sequenced Psilotum. Complete chloroplast genome sequences can provide a wide variety of information. By comparing several sequences it is possible to identify large-scale structural rearrangements. These are presumably rare events that can be used to mark evolutionary branches. Although such structural information can be obtained with DNA hybridization and mapping, current technology suggests that sequencing can be more cost effective and new taxa can be added one at a time without the need for cross hybridizations at each addition. Furthermore, data at the sequence level can be used to identify length polymorphisms of any size, and to ensure that length differences of similar size are indeed homologous in position. I am currently sequencing the chloroplast genome of the leptosporangiate fern Adiantum and have initiated similar projects for the lycopod Huperzia and also for Equisetum. A fourth project for the near future will be the basal fern Osmunda. Chloroplast genomes rarely recombine so that phylogenetic signal is retained longer than for many nuclear regions. Chloroplast-wide genome data may also enable us to identify genes (other than those already used) for phylogenetic utility at different levels. Resultant data should enable us to learn more about how genomic structural rearrangements occur, patterns of gene movement between plastid and nuclear genomes, and the evolution of many of the important photosynthetic genes, most of which are located on the chloroplast genome. Thus, my current research relates to the RCN proposal from both sides: my past and current research in vascular plant phylogenetics, and my current and future studies in plant genomics. I could thus benefit from new contacts in both areas, and provide experience in bridging the gap, especially with regard to phylogenetic analysis on a genomic scale.