Cecilia I Banag1,2, Arnaud Mouly3, Grecebio Jonathan D Alejandro4,5, Birgitta Bremer6, Ulrich Meve7, Guido W Grimm8, Sigrid Liede-Schumann7. 1. Department of Biological Sciences, College of Science, University of Santo Tomas, España Boulevard, 1015, Manila, Philippines. cibanag@ust.edu.ph. 2. Research Center for the Natural and Applied Sciences, University of Santo Tomas, España Boulevard, 1015, Manila, Philippines. cibanag@ust.edu.ph. 3. UMR CNRS 6249 Chrono-environnement, Université Bourgogne - Franche-Comté, 16 Route de Gray, 25030, Besançon cedex, France. 4. Department of Biological Sciences, College of Science, University of Santo Tomas, España Boulevard, 1015, Manila, Philippines. 5. Research Center for the Natural and Applied Sciences, University of Santo Tomas, España Boulevard, 1015, Manila, Philippines. 6. Bergius Botanic Garden, Stockholm University, 106 91, Stockholm, Sweden. 7. Department of Plant Systematics, University of Bayreuth, Universitätstraße 30, 95440, Bayreuth, Germany. 8. , Orléans, France.
Abstract
BACKGROUND: The Philippine archipelago is globally one of the most important model island systems for studying evolutionary processes. However, most plant species on this archipelago have not yet been studied in sufficient detail. The main aim of this study is to unravel the evolutionary history and biogeographic relationships of the Philippine members of the pantropical genus Ixora. RESULTS: The complex plastid and nuclear divergence patterns in Philippine Ixora, documented using tree and network approaches, reveal a highly dynamic evolution in Ixora, involving several phases of radiation and recolonization. Philippine Ixora comprises at least five lineages, of which one is most closely related to species from Wallacea, and the remaining four to species from Asia. CONCLUSIONS: Our study highlights the importance of Philippine species for understanding phytogeographic patterns in the Indomalayan-Australasian eco-region. The overall genetic differentiation, as well as the incongruence between genealogies based on the biparentally inherited nucleome and the maternally inherited plastome in Ixora, reflect the complex tectonic history of the Philippine archipelago. The Ixora lineage related to Wallacean species supports the delimitation of different ecozones along Huxley's line, because it is absent from Palawan. The remaining four lineages are all allied with Asian taxa, reflecting several waves of colonization. Close relationships between some widespread Philippine species and locally adapted narrow endemics suggest that the widespread, genetically diverse species act as pools for the formation of new species in a process of ongoing speciation. Our results suggest that the species concepts of some of the more widespread taxa need to be revised.
BACKGROUND: The Philippine archipelago is globally one of the most important model island systems for studying evolutionary processes. However, most plant species on this archipelago have not yet been studied in sufficient detail. The main aim of this study is to unravel the evolutionary history and biogeographic relationships of the Philippine members of the pantropical genus Ixora. RESULTS: The complex plastid and nuclear divergence patterns in Philippine Ixora, documented using tree and network approaches, reveal a highly dynamic evolution in Ixora, involving several phases of radiation and recolonization. Philippine Ixora comprises at least five lineages, of which one is most closely related to species from Wallacea, and the remaining four to species from Asia. CONCLUSIONS: Our study highlights the importance of Philippine species for understanding phytogeographic patterns in the Indomalayan-Australasian eco-region. The overall genetic differentiation, as well as the incongruence between genealogies based on the biparentally inherited nucleome and the maternally inherited plastome in Ixora, reflect the complex tectonic history of the Philippine archipelago. The Ixora lineage related to Wallacean species supports the delimitation of different ecozones along Huxley's line, because it is absent from Palawan. The remaining four lineages are all allied with Asian taxa, reflecting several waves of colonization. Close relationships between some widespread Philippine species and locally adapted narrow endemics suggest that the widespread, genetically diverse species act as pools for the formation of new species in a process of ongoing speciation. Our results suggest that the species concepts of some of the more widespread taxa need to be revised.