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

摘要

RAPD marker technology was used to assess evolutionary relationships among species classified in the Oocarpae and Australes subsections. A total of 127 RAPD markers was assessed across 10 taxa in Oocarpae and 8 taxa in Australes. A phylogenetic tree was constructed by neighbor-joining analysis of a p-distance matrix generated from the marker data. Results indicate that taxa in the California Oocarpae are distinct from Mesoamerican Oocarpae and Australes. The Mesoamerican Oocarpae and Australes are closely aligned and apparently are derivatives of a common progenitor, most likely ancestral Pinus oocarpa. The Mesoamerican Oocarpae subsection is polyphyletic, sharing ancestry with taxa from the Teocote subsection. We propose an evolutionary scenario that suggests that an ancestor of Oocarpae migrated south through Mexico and Central America, as well as east across the southern US, with the two paths converging in Florida or the Caribbean. Pinus caribaea var. hondurensis 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, having diverged from ancestral Oocarpae as this subsection moved east. Subsequent divergences within Australes produced P. echinata and P. taeda.