The Origin of Caribbean Pine in the Seasonal Swamps of the Yucatán

An isolated 180‐ha stand of Pinus caribaea var. hondurensis (Caribbean pine) exists at El Pinal, Guatemala, in seasonal marshlands 18 km northeast of the old Mayan capital city of Tikal. One hypothesis suggests that during the zenith of their culture between 600 and 900 AD, the Mayans planted the pine stand as a source of resinous lighter wood (ocote) to start cooking fires. We examine the alternate hypothesis that El Pinal is of natural origin. Allozyme analyses were used to compare genetic diversity levels at El Pinal with seven neighboring natural stands of Caribbean pine in Belize and Guatemala. Results indicated that the El Pinal population had a high proportion of polymorphic loci (88%), had four unique alleles, exhibited an outcrossing rate of 91%, and differed little from larger natural populations of Caribbean pine located 65–100 km away. Only 2.3% of the total genetic diversity (GST) was found among the eight populations, which suggests high historic levels of gene flow. A climatic model (FloraMap) that used data from 36 known pine provenances of Caribbean pine to predict the distribution of new populations examined differences between current and predicted geographic ranges of the species. The model predicted that Caribbean pine should occur ($$P> 40% $$) along the east coast of the Yucatán as far north as Puerto Juarez, Quintana Roo, Mexico, where it does not exist today. Genetic analyses indicate that El Pinal represents a population of ancient origin, and the climatic model indicates that El Pinal might have belonged to a larger historic distribution of Caribbean pine that occurred in the Yucatán when climates were drier than today.