on-going research

PHYLOGENETIC SYSTEMATICS:
Many of the projects in the lab involve estimating phylogenetic relationships, generally with DNA sequences, but also with morphological data. In collaboration with colleagues, Michael is now working on several plant groups, including various Dipsacales and a variety of small groups related to the biogeography project. He is also working with Sarah Mathews (University of Missouri, Columbia) on analyses of seed plants and angiosperms using phytochrome genes. Here, a special interest is the use of duplicated genes in rooting trees. Michael also continues a long term collaboration with David Hibbett (Clark University) on the phylogeny of basidiomycete fungi. In the lab at Harvard, Rick Ree recently completed his PhD on Pedicularis (Scrophulariaceae) from China, Kobi is working on Symphonia (Clusiaceae) from Madagascar, and Chuck Davis is working on Malphigiaceae from Africa. At Yale, Chuck Bell is working on the phylogeny of Valerianaceae, and Richard Winkworth on Apiaceae in New Zealand and Viburnum in North America. At the moment we are particularly interested in exploring the use of various nuclear genes, especially to find suitable markers for species/population level problems.

CHARACTER EVOLUTION:
Many lab projects also involve studies of character evolution using phylogenetic trees. Some of these are focused on individual characters of interest (such as flower symmetry in Asteridae, breeding systems in monocots, herbaceousness across angiosperms, or gills and ectomychorrizal habit in basidiomycetes). A number of these studies have made use of maximum likelihood approaches and a variety of "comparative methods". Others studies seek general patterns in the frequency and distribution of homoplasy (such as the work with Mike Sanderson, UC Davis, on levels of homoplasy in relation to confidence, etc.). Michael (in collaboration with recent graduate Rick Ree) is especially interested in developing a general model to explain levels of homoplasy, involving number of character states and rates of change as key variables.

DIVERSIFICATION:
Several projects in the lab focus on patterns of diversification. These involve the relevant conceptual issues, the development of phylogeny-based methods, and the compilation of empirical data, mainly on angiosperms. For example, Chuck Bell is looking at diversification rates in Valerianaceae, especially in South America, and Richard Winkworth is interested in the historical factors that have had an important impact on patterns of diversification in the flora of New Zealand. Brian Moore is looking at the effect of growth form (especially herbaceous habit) on diversification rates in flowering plants, and also collaborating with Kai Chan (Princeton University) to develop more robust methods for detecting shifts in diversification rates and testing key innovation hypotheses.

BIOGEOGRAPHY:
Michael has been working on the biogeography and the historical assembly of plant communities around the Northern Hemisphere. This work is being pursued in collaboration with many others in the lab, including former postdocs Jianhua Li (Arnold Arboretum), and Kathy Gould (Brooklyn Botanical Garden), and current lab members Chuck Bell and Chuck Davis (Harvard). Chuck Bell is especially interested in the historical biogeography of Valerianaceae, and Richard Winkworth is interested in geographic patterns in the Southern hemisphere, especially the origin of the alpine flora of New Zealand. Kobi is trying to understand how the African and South American Symphonia are related to the species in Madagascar, and Chuck Davis is especially interested in the origin of disjunctions between South America and Africa in Malphigiaceae. Brian has recently completed a paper on using parasite data to infer host phylogeny and biogeographic history.

HISTORICAL ECOLOGY:
Several members of the lab are working to dovetail ecology and phylogeny. Cam Webb is exploring the application of phylogenetic methods to problems in community ecology, with special emphasis on tree communities in Borneo. He and Michael and several other colleagues are writing a review of this approach. Erika especially interested in leaf and phenological characteristics as these relate to climatic shifts.