Assessing evolutionary relationships of pines in the Oocarpae and Australes subsections using RAPD markers

RAPD marker technology was used to assess evolutionary relationships among species classified in the Oocarpae and Australes subsections. A total of 12 7 RAPD markers was assessed across 10 taxa in Oocarpae and 8 taxa in Austra les. A phylogenetic tree was constructed by neighbor-joining analysis of a p-distance matrix generated from the marker data. Results indicate that tax a in the California Oocarpae are distinct from Mesoamerican Oocarpae and Au strales. The Mesoamerican Oocarpae and Australes are closely aligned and ap parently are derivatives of a common progenitor, most likely ancestral Pinu s oocarpa. The Mesoamerican Oocarpae subsection is polyphyletic, sharing an cestry with taxa from the Teocote subsection. We propose an evolutionary sc enario that suggests that an ancestor of Oocarpae migrated south through Me xico and Central America, as well as east across the southern US, with the two paths converging in Florida or the Caribbean. Pinus caribaea var. hondu rensis is intermediate between the Mesoamerican Oocarpae and Australes, and its ancestors formed the species line that migrated to the US from Central America. Pinus palustris is the oldest of the Australes species studied, h aving diverged from ancestral Oocarpae as this subsection moved east. Subse quent divergences within Australes produced P. echinata and P. taeda.