The plant genus Hedyotis is a group of nearly 180 Asian-Pacific tropical species in the plant family Rubiaceae (the coffee family). Hedyotis and its related genera are currently taxonomically ill-defined groups. Hedyotis exhibits high levels of species endemism, with many species occurring on a single island or mountain, and its closest relatives occur in Africa and America. Additionally, some of the island and high elevation species in the Hedyotis-Oldenlandia complex have evolved from herbaceous ancestors into small trees. This is known as secondary woodiness, and is often specific to islands or island-like habitats. By building a phylogeny using DNA and morphological data, this project aims to improve the classification of the group, investigate broader issues of ancient dispersal patterns, and examine the evolutionary development of secondary woodiness in the Asian and Pacific species.
This project will resolve the classification of the fourth largest plant family (Rubiaceae), and improve plant collections and botanical knowledge from five under-collected biodiversity hotspots. Additionally, this research will build partnerships with international institutions in six countries, foster collaborations between scientists, and train students in phylogenetics, botany, and taxonomy.
The aim of this dissertation research project is to address three broad but related issues; the taxonomy, the evolution of secondary woodiness, and the historical biogeography of the Hedyotis-Oldenlandia complex in the plant family Rubiaceae, with special focus on Asian-Pacific lineages. The project started in May 2012 with fieldwork in China, Thailand, India and Nepal. This fieldwork enabled us to collect 101 specimens from Hedyotis-Oldenlandia complex. The DNA of these specimens were sequenced and combined with an existing data set, resulting in a comprehensive sample from Asia. The data from the project resulted in a publication (Wikström et. al. 2013) dealing with all major clades (groups of organisms descended from a single ancestor) within the Hedyotis-Oldenlandia complex in Asia and the Pacific. Defining new clades in Wikström et al. (2013) led to another manuscript, which is ready to be submitted to a journal. These two publications address taxonomic issues by defining new genera in the Asia-Pacific region and thus fulfilling one of the three major goals of the project. With the well-sampled phylogeny (evolutionary tree) in hand, studies of secondary wood evolution and historical biogeography are underway. We plan to complete these two studies within the next two years before the successful completion of doctoral degree of Co-PI (Suman Neupane). The project also enabled Co-PI (Suman Neupane) to visit Naturalis Biodiversity Center in the Netherlands for wood anatomical study. Wood samples from 34 species were studied that will be incorporated into the secondary wood evolution study. This visit also made it possible to study the herbarium specimens of the Hedyotis-Oldenlandia complex housed in Naturalis and the National Botanic Garden, Belgium. The records obtained from the rich herbarium collections in these two herbaria improved and updated our list of the current geographical locations of the species. The updated list of geographic ranges of species will be used for further biogeographic study. The project also allowed us to present our results on new taxonomic combinations in the annual meeting of the Botanical Society of America (Botany 2013) in New Orleans, LA. We will be presenting preliminary findings in secondary wood evolution in the upcoming Evolution conference (Evolution 2014) in Raleigh, NC in June 2014. Finally, the support provided by the NSF DDIG played an instrumental role in formulating a successful doctoral dissertation research project by allowing the researcher to preform a bulk of the task related to fieldwork and sample collection. The outcomes of the project are hoped to solve taxonomic inconsistencies existing within Hedyotis-Oldenlandia complex and contribute to a better understanding of secondary wood evolution and biogeographic history of Asia-Pacific region. Reference: Wikstrom, N., Neupane, S., Karehed, J., Motley, T. J., & Bremer, B. (2013). Phylogeny of Hedyotis L.(Rubiaceae: Spermacoceae): Redefining a complex Asian-Pacific assemblage. Taxon, 62(2), 357-374.