Evolution and historical biogeography of Pacific Coprosma (Rubiaceae)

Abstract

This dissertation investigated the evolutionary history and historical Coprosma of Coprosma (Rubiaceae) across the Pacific Ocean. A brief introduction to the status of Pacific biogeography of angiosperms is discussed in Chapter 1 along with an introduction to the systematic relationships and previous research of the genus Coprosma itself. Chapter 1 ends with a description of the dissertation aims and hypotheses. The first research based chapter is Chapter 2, which aimed to elucidate the evolutionary history to the Hawaiian Islands using molecular phylogenetic analyses followed by an assessment of phylogeographic patterns within the genus. The analyses inferred two independent colonization events of Coprosma to the Hawaiian Islands: one radiation of 12 orange-fruited taxa from the Marquesas Islands or Austral Islands, and a separate independent colonization for one black-fruited species from an unclear origin. Research of Chapter 3 investigated the historical biogeography of the genus across a wide geographic distribution with many more species represented using molecular clocking techniques. The analyses inferred that Coprosma diverged from Nertera in New Zealand during the Oligocene. Subsequent diversification of New Zealand taxa was correlated temporally with tectonics of the Miocene. It was also inferred that at least 30 bird mediated long distance dispersal events, primarily within the last 10 Ma, have occurred in order to explain the extant distribution of the genus. Chapter 4 investigated the evolutionary inheritance of morphological traits, which were traced onto phylogenetic reconstructions of the genus. Resulting from this work, a key and new taxonomic description that includes six newly circumscribed subgenera was completed. Chapter 5 synthesizes the dissertation research which has elucidated a complex novel evolutionary history of Coprosma which is one of the most widespread and species rich genera in the Pacific.