Systematic Studies in the Tropical Woody Polygonaceae

The Polygonaceae is a family of plants perhaps best known for its foodstuffs (Rheum and Fagopyrum) and its weeds (Rumex, Persicaria, and Polygonum). These better-known plants are almost exclusively temperate in distribution and herbaceous in habit. Yet, the Polygonaceae also includes a number of tropical and woody taxa. The disparity of knowledge between temperate and tropical taxa is a wide-ranging historical phenomenon in systematics generally. Tropical ecosystems also provide unique opportunities to investigate speciation processes, such as those associated with islands, the major island systems being largely tropical. This dissertation focuses on two genera of the Polygonaceae: Coccoloba and Triplaris, both tropical, both woody. As a result, in this dissertation I aim to do two things. First, I aim to increase our basic knowledge about these genera and contribute to lessening the disparity in knowledge between tropical and temperate genera. Second, in studying these genera, I hope to use them to better understand speciation processes generally. A phylogenetic and biogeographic study of Coccoloba revealed a deep phylogeographic rift between the South American species and the species in Mesoamerica and the Caribbean. Coccoloba appears to have its origin in Mesoamerica and then dispersed south, in contrast to what had been previously thought. There is low genetic divergence among species of Coccoloba, suggesting perhaps a rapid expansion. In Triplaris, a nomenclatural synopsis revealed that some historical nomenclatural problems could be resolved but that some problems remain, particularly the problem of missing type specimens. The nomenclatural investigation revealed some species complexes. A subsequent morphometric analysis of these species complexes showed that some recognized taxa appear to be more than one species, in particular, Triplaris americana. I recommend that T. estriata be rehabilitated