Studies of Mesoamerican tropical trees: Trees of the Maya region and a case study on the ethnobotany and phylogeography of cacao (Theobroma cacao L.)

This study explores the diversity of tropical trees at two different scales: (1) Development of an identification and information system for the most common tropical trees of Belize, Guatemala and Southern Mexico, and (2) A case study on the ethnobotany and phylogeography of cacao ( Theobroma cacao L.). At the larger scale, the methods and techniques used to implement an interactive computerized system for the taxonomic identification of the most common trees of the lowland Maya areas are described. A relational database provides access to scientific names, synonyms, common names, distributions, 4,000 images and 2,000 references for 60 families, 254 genera and 598 species of trees. The case study of the ethnobotany and phylogeography of Theobroma cacao L. includes two parts. The first part is based on historical accounts and fieldwork, and describes the ancient and current distribution of cacao in Mexico. The results suggest that most populations actually found in areas where no commercial cultivation of T. cacao has taken place in recent times are remnants of pre-Hispanic plantations. Evidence shows that T. cacao ssp. cacao was the main subspecies cultivated; however, it also suggests that T. cacao ssp. sphaerocarpum was probably introduced in Mesoamerica by “the Valdivia” fifteen hundred years ago. It is concluded that the Spanish were not responsible for bringing the cultivation of cacao to South America.; The second part explores the molecular variation in the chloroplast and nuclear genomes of T. cacao and applies a phylogenetic method to reconstruct phylogeographic patterns at the population level. No useful variation for maximum parsimony analysis was found in fragments of the chloroplast genome. Molecular variation was found in the nuclear gene G3pdh and a parsimony analysis was conducted to confirm the monophyletic status of T. cacao. A statistical parsimony analysis was performed to describe the genetic structure of cacao populations in Mexico. Twenty-one haplotypes were found showing a congruent pattern of restricted gene flow. The oldest haplotype is represented by the wild individuals found in the Lacandon and Calakmul tropical rain forests suggesting that this area is source of the cacaos cultivated in Mesoamerica before the arrival of Spanish.