Research

Most of my time is devoted to teaching, but I conduct research at UF with undergraduates, and have several continuing projects. Students who are interested in participating in research are welcome to contact me to discuss shared interests and opportunities.

Divergence and diversity of rare species of the Fall-Line Sandhills

I have been involved since 2007 with a project which attempts to understand the relationships between rare taxa endemic to the Sandhills region of the Carolinas, Virginia, and Georgia. This is part of a cooperative effort to understand the ecology and evolution of rare plant species that are found on the Ft. Bragg Army installation as well as a few other military and non-military sites. This is in collaboration with Wade Wall (US Army Corps of Engineers). To date, three manuscripts have been published dealing with divergence population genetics of Pyxie Moss, Pyxidanthera brevifolia (Diapensiaceae, pictured above), the Sandhills Lily, Lilium pyrophilium (Liliaceae), and Astragalus michauxii, (Fabaceae), which will be important for the conservation of these taxa. Undergraduate students in my lab at University of Florida have been working on developing microsatellite markers for additional species of concern, such as Rhus michauxii (Anacardiaceae).

Phylogenetics & phylogeography of Chihuahuan Desert gypsum endemic plants

I collaborate with Mike Moore (Oberlin College), Hilda Flores-Olvera, and Helga Ochoterena (Universidad Nacional Autónoma de México) to study the evolution of the gypsum-adapted flora of the Chihuahuan Desert in the southwestern US and northern Mexico. The Chihuahuan Desert is unique among the four regional deserts of North America in its overwhelming preponderance of calcic rocks and soils. Most of the surface of the Chihuahuan Desert is derived from limestone (calcium carbonate), but a significant portion is comprised of gypsum (calcium sulfate). Gypsum occurs as layers of primary rock, often interleaved between layers of limestone, or as secondary deposits in the form of clays or evaporites. In either case, gypsum soils are characterized by a hard, brittle crust, which is not amenable to seedling establishment. Gypsum deposits are therefore occupied by a different -and very diverse- suite of species than the surrounding desert. These species are edaphic endemics, that is, they are restricted to these soils. Because these soils are discontinuous, the endemics are generally isolated from other populations. In fact, many species are unique to particular “islands” of gypsum. Our project is using several genetic techniques from traditional sequencing and microsatellites, to targeted sequence capture to reconstruct the evolutionary history of these endemic taxa in order to determine: How frequently gypsum endemism has arisen (how easy is it to evolve an edaphic specialization?) How old are edaphic endemic lineages (are these highly specialized plants able to withstand climate change, etc. and diversify in spite of specialization and low population sizes?) And how interconnected are these populations genetically (what affects the amount of gene flow between isolated populations?) Undergraduate students at UF have been involved in generating and analyzing microsatellite data for Dicranocarpus parviflorus (Asteraceae) and Sporobolus nealleyi (Poaceae).

Systematics of Nyctaginaceae

My dissertation work focused on the evolutionary history of the Four O’clock Family, Nyctaginaceae. This group is best known for the four o’clocks (Mirabilis jalapa) and Bougainvillea (Bougainvillea glabra, B. spectabilis). I completed a phylogenetic study that established the relatedness of the North American xerophytic genera, (Boerhavia, Okenia, Anulocaulis, Nyctaginia, Cyphomeris, Commicarpus, Mirabilis, Allionia, Abronia, and Tripterocalyx) and revised the classification of the family. I am currently preparing a phylogenetic study of the widespread genus Boerhavia, which has, like the family as a whole, undergone a radiation in the deserts of North America, and collaborate with other students of this vexing family. This work meshes with my current work on the gypsum endemic flora, which includes several Nyctaginaceae.