I am interested in the diversity and evolution of spore-dispersed plants, especially ferns and clubmosses. My career-long fascination has been with the biogeography and diversification  of these plants and the ecological and geological variables that determine these patterns. I have for five decades been exploring the origins of diversity via hybridization and polyploidy as well as through primary divergence.

For many years here at the University of Vermont I have been fortunate to be surrounded by a community of superior scholars and students working together on an array of inquiries into the diversity and evolution of spore-dispersed plants, especially ferns and clubmosses. For the last two decades, I have enjoyed working in partnership with Michael Sundue, who while he was assistant curator dramatically improved the worldwide scope and activity of the Pringle Herbarium worked with me to train some of the best students to ever work on systematics at UVM.

Though we usually have worked on ferns (notably Adiantum, Athyrium, Dryopteris, Grammitidaceae, Matteuccia, Polystichum, Phegopteris, Pleopeltis, Rumohra,  Polypodium, and Thelypteridaceae) and Lycophyes (Huperzia and Phlegmariurus), we have been known to work on flowering plants (including Attalea, Carex, and Lathyrus) as well. All of our more recent projects include molecular genetic analysis of the plants: our data sets have included an array of chloroplast and nuclear DNA markers.   In the last few years, we have added target-capture sequences to our array of data, at first for phylogenetic analysis  and now for analysis of genomic constitution of hybrids and polyploids.

At the same time, I am  deeply interested in the evolution of plant structures, so working together with the people here I  have developed a number of tools for representing plant structural features and analyzing them phylogenetically. A particular fascinationof mine is with the morphometrics of spore size and shape.  

Now, in 2023, it is a time of transition at  UVM and the Pringle Herbarium. I look to be promoted to emeritus in July, after which I will devote full time to my research program, to the three PhD students remaining in our lab, and supporting the new generation of systematists here at the Pringle Herbarium.  My fervent hope is to provide some real insight into the systematics and evolution of Polystichum near and above treeline in the tropical Andes in the time remaining to me.