We occupy a mow, once part of a cotton mill, in Durham, North Carolina, and the back wall, beside a tall window, consists mostly of a large door, sealed now by fresh, white paint, where cotton bales may have passed. The mow is now a conference room, and we fill the space of a long table. I sit for the week near the back, by the tall window of 24 panes, and I turn periodically to watch the light change, the rain fall, and the branches of a tree, sometimes steady and sometimes wavering in the wind. The mow, table, window, and the ideas we discuss are part of the National Evolutionary Synthesis Center (NESCent).
NESCent is funded by the National Science Foundation to advance synthetic research on basic questions in evolutionary biology. I am part of a working group that is funded by the center to explore the evolution of flowers. Our working group, which consists of plant biologists from various universities and botanical gardens in North America, Mexico, and Europe, including well established scientists as well as some who are early in their careers, begins with a morning and more in which each of us gives a brief talk about the issues and questions that drive our research. Show no more than five slides and talk for no more than ten minutes, we have been told, and we each condense our work, sometimes from decades, into haiku, a few bright lines that evoke the scene of our ideas and the seasons of our outlooks on the evolutionary landscape.
Here is what I say: Patterns of plant diversity in nature drive my curiosity and research questions. I try to understand diversity by first building evolutionary trees, so-called phylogenies, that show relationships among lineages of plants. Using phylogenies, I characterize diversity patterns we see among the forms of plants, and I ask about evolutionary processes that may have created those patterns. My research also uses phylogenies to revise classifications of plants. For example, I like to model existing or previous classifications as phylogenies to test whether they are robust to the evolutionary signals we find DNA sequence data. For the past few years in my lab, we have also been asking questions about geographical patterns of diversity. This research uses the distribution of genetic diversity in populations and species of plants to reconstruct migration patterns and evolutionary processes, and I have been especially directed this work toward understanding the history of plants in the American West.
The brief talks serve as introductions, although we are each largely familiar with the interests and publications of the others in the room. The talks serve also to place perspectives on the table so that we can see the positions and experiences that will come to play over the week.
We finish the first day by discussing what we want to achieve and some preliminary analyses that the organizers have conducted to stimulate conversation. One of the issues that we wish to explore is whether certain sets of floral attributes have evolved to co-occur independently many times in different groups of plants. Such independent origins of co-occurring traits are often seen as a signature of evolutionary adaptation but one in which diversity, shaped by natural selection in similar environments, converges on a few handfuls of common forms. In flowers, these are forms like petal tubes that have few stamens, which have been repeatedly selected by pollinators such as moths and butterflies that have long mouth parts and hummingbirds that have long, narrow beaks. A second issue that we wish to address is more general, and that is how the grand diversity of flowers has been assembled through evolutionary time. This question is one that many of us have investigated and written about repeatedly for many decades; it is a question that concerned biologists and natural historians well before any of us in the NESCent mow began our work on flowers.
The synthesis we wish to achieve will need to come from fresh analyses but not from fresh data. We will borrow data from the scientific literature, but we will build a new framework to analyze those data. The discussions of our working group target that framework. Where will we get the phylogeny that will serve as the basis for our analysis? How many plant groups must we sample and how will we sample those groups? What attributes of flowers do we wish to include in the study and how do we characterize those attributes? Once we have the selected the plant groups, reconstructed the phylogeny, and have our data on the characters of flowers, how will we conduct the analyses? These are the questions we discuss on Wednesday, Thursday, and Friday.
We meet each morning at 8.00 to take a van to the old mill, where we grind ideas in the mow until 7.00 p.m., when we break to have dinner together. The days are mentally exhausting, but I am also physically tired each evening. Synthesis is hard work, and I fall asleep early and quickly each night.