The identification of isolating barriers to gene flow (their relative contribution, the order in which they accumulate), is a current challenge in the study of plant speciation. By combining systematics, phylogenetics, and comparative methods, a broad picture of the process of speciation through time and across space can begin to be pieced together.
Speciation is a composite of many little steps - it is gradual and continous. My work tries to identify some of those little steps in a genus of wildflowers in the north American west -- Castilleja, also known as the 'paintbrushes'. Much of my work is at the tips of the Castilleja phylogeny, closely examining species boundaries and tallying species criteria. I also work deeper in the phylogeny, examining diversification events further back in time, in an effort to identify traits that appear correlated with diversification in the group as a whole.