I try to understand evolutionary transitions related to origin and early diversification of land plants, which likely occurred more than 500 million years ago. My students and I use phylogenies, together with molecular, physiological, ultrastructural, paleontological, and ecological methods, to trace the first appearance of fundamental plant features such as embryo, cuticle, walled spores, meristems, plastid carbonic anhydrases, and bacterial and fungal associations. This work necessarily focuses on charophycean green algae--the modern protists most closely related to plants, and bryophytes--the earliest-divergent plant lineages.
Recent research students have worked on: 1) molecular ecology of eubacteria associated with peat mosses (Sphagnum spp.) from northern Wisconsin bogs, with an emphasis on methane oxidizers, 2) molecular ecology of eubacteria associated with charophycean green algae of northern Wisconsin bogs, with an emphasis on nitrogen fixers, 3) evolution of meristems, plasmodesmata, and cuticles, 4) Ordovician fossils from the Madison area, including bryophyte-like remains and the earliest-known fossil fungi (Glomales, a group known to commonly form symbiotic associations with plants), 5) hexose transporter genes and proteins of charophycean algae and bryophytes, 6) TEM immunolocalization studies and activity measurements of carbonic anhydrases in charophycean algae.
Our work has also contributed to understanding peatland ecology and the formation of nuisance algal blooms in acidified lakes, both of importance in northern temperate ecosystems. With a Chilean colleague, we are interested in comparative studies of northern and southern hemisphere peatland microbial ecology. We also work closely with a local biotechnology company to develop applications involving algae and bryophytes.
I teach courses in the biology of algae and bryophytes and introductory botany for non-majors, and contribute to a large introductory majors biology course.