Systematic Studies in Myrtaceae of the Greater and Lesser Antilles

Abstract

The Myrtaceae, or myrtle family, are a group of flowering trees and shrubs represented in the Americas by over 2000 species of the predominantly Neotropical tribe Myrteae. Recent progress on the challenging systematics of the group has been achieved through molecular phylogenetics, but few of the almost 500 species endemic to the islands of the Greater and Lesser Antilles in the Caribbean have been included in either phylogenetic or revisionary studies. The purpose of my dissertation is therefore to contribute to the description and phylogenetic classification of Antillean Myrtaceae. The first study describes Eugenia walkerae, a new species of conservation concern endemic to the island of Anguilla in the Lesser Antilles. The second study surveys the diversity of Myrtaceae present in the Greater Antilles. Members of all genera native to the region were sampled through field work across the region and included in a phylogeny inferred from one nuclear and three chloroplast genetic regions with known representatives of major clades. On the basis of the results, three Greater Antillean endemic genera (Calyptrogenia, Hottea, and Mitranthes) are reduced to synonyms, Pseudanamomis and Calycolpus sensu Bisse are found to be polyphyletic, and the Greater Antillean species of Plinia are included within Myrciaria. The presence of two new lineages in the region within subtribe Myrtinae and Eugenia is also identified. The third study revises the taxonomy of the Lathberry Clade, a novel group of seven species of Eugenia distributed from Puerto Rico through the Lesser Antilles. The morphology and seed coat structure of each species of this clade were examined from herbarium material, and a phylogeny was inferred from three non-coding nuclear genetic regions. The results of these investigations are summarized in a taxonomic treatment including extinction risk assessments. My dissertation shows that the outstanding diversity of Myrtaceae in the Greater and Lesser Antilles consists mostly of species of major lineages also found on adjacent continents. It also lays a foundation for further descriptive and phylogenetic work needed to advance the systematics of Myrtaceae in the region.