Systematics, Biogeography and Leaf Anatomy and Architecture of Bursera subgen. Bursera (Burseraceae) in the Greater Antilles and the Bahamas

Abstract

This dissertation presents a comprehensive study on the origin and evolutionary relationships of the species of Bursera in Cuba, Hispaniola, Jamaica and the Bahamas. The goals of the first chapter were to test monophyly of the group, revisit a recent transfer of two species of Bursera to Commiphora, and place recently discovered mainland species using the reconstructed phylogenies. Additionally, divergence estimations using fossils were used as independent tests of several hypotheses regarding the arrival of the modern biota to the Greater Antilles and Bahamas (GAB). I conclude that all endemic taxonomic entities of the genus in this region belong to Bursera subgen. Bursera but that two separate lineages colonized the GAB via dispersal. The genus diversified during the Middle Miocene to Pliocene, and the data corroborate several paleogeographic events during that interval. The second chapter presents informative characters from leaf anatomy and leaf architecture for the 14 endemic species of Bursera distributed in the GAB. There is evidence for some evolutionary tendencies in the group, among them a trend toward small, simple, amphistomatic and unifacial leaves, character states for which ecological correlates can now be studied. Morphological and anatomical evidence corroborates phylogenetic results in suggesting that a population of B. glauca in Cuba is a new species. Finally, the third chapter constitutes the first taxonomic account and description of all known endemic species of Bursera in the region and reflects the results of the previous chapters. The primary results are as follows: (1) a new species from eastern Cuba, B. yaterensis, is described; (2) five species of Commiphora are returned to Bursera; (3) B. nashii is treated as conspecific with B. glauca; and (4) B. ovata is treated as conspecific with B. trinitensis. A dichotomous key is provided using mostly vegetative characters due to the frequent lack of adequate reproductive material and the relative uniformity of most floral and fruit characters. Each species description includes leaf architecture (morphology and venation pattern) and anatomy, introducing characters that could and should be used for describing and distinguishing other Bursera in Meso- and South America as well as for African Commiphora.