In Hawai'i, there are eleven putative species within the Psychotria (Rubiaceae, Coffee family) genus. The Hawaiian Psychotria (kōpiko) exhibit various distribution patterns where some species are rare and narrowly distributed, such as the endangered Psychotria grandiflora, while others are widely distributed and found on the majority of islands. When species within a single genus exhibit contrasting distribution patterns, understanding the drivers for commonness and rarity are important for conservation and management planning especially in the face of climate change. In an effort to understand factors contributing to rare species' distributions, we studied a widespread species, Psychotria mariniana. Rare species are inherently difficult to study, so examining a closely-related, but more common species can provide insight into the causes of commonness and rarity. We conducted a phylogenetic and population genetic analysis using field-collected and herbarium-sampled P. mariniana from six different islands. We inferred two species-level phylogenies using nuclear (ITS and ETS) and chloroplast markers (matK, psbA, and psbE) where different P. mariniana populations formed monophyletic groups, both within and among islands. These data provide evidence of inter-island and intra-island population structure. We aim to further analyze population genetics using 12-15 microsatellite loci to compare gene flow estimates, allele frequencies, and heterozygosity measures among all populations. These data, along with ecological data, aim to shed light on historical distribution patterns and factors contributing to the success of P. mariniana to provide sufficient, beneficial information to Hawai’i’s Plant Extinction Prevention (PEP) program regarding conservation of the endangered Psychotria.
• The Hawaiian Islands are known as a hotspot archipelago and the island chain is linearly and chronologically arranged
• Island chain consists of 8 major islands where Kaua’i is the oldest and the Big Island is the youngest (Funk & Wagner, 1995)
• Psychotria mariniana is a native, endemic, wild coffee species found on six of the eight major islands in native mesic to wet forests and high-elevation ridges and cliffs
• Individuals are self-incompatible and rely on pollinators for outcrossing (Watanabe et al., 2014)
• Psychotria mariniana is the most widespread species of the eleven Hawaiian Psychotria species (Zhang et al., 2016)
• Examining a single species in the early stages of divergence will not only enable us to understand the historical speciation of the Hawaiian Psychotria (Progression rule hypothesis: chronological dispersal pattern from oldest to youngest island), but also shed light on the factors contributing to genetic divergence on the Hawaiian Islands and our understanding of the factors driving successful distributions.
• My goal is to document and quantitively describe the intraspecific variation of Psychotria mariniana by using molecular markers and ecological niche modeling (ENM) to answer the following questions:
(1) Does the current P. mariniana distribution pattern mirror historical island emergence patterns (Progression rule hypothesis)?
(2) Why and how is P. mariniana successful at widespread colonization, while other species are limited to one or few islands?
(3) Can rarer populations recover by adjusting conservation efforts to mirror these characteristics deemed successful?
• Collected 275 Psychotria mariniana individuals from 9 different populations on Kaua’i, Oahu, Maui, and the Big Island
• Destructively sampled 46 herbarium specimen representing Moloka’i and Lana’i from the Bernice Pauahi Bishop Museum (BISH) and National Tropical Botanical Garden (NTBG)
• Extracted DNA using CTAB extraction method
• Ran Polymerase Chain Reaction (PCR) to amplify nuclear (ITS and ETS) and chloroplast (matK, psbA, and psbE) markers to investigate relationship between populations
· Nuclear phylogeny depicts genetic differentiation between P. mariniana populations found on different islands (i.e. KFR clade)
· Based on nuclear data, Kaua'i's Pihei and Alakai Swamp Trail populations and P. wawrae and P. mariniana Kaua'i individuals are monophyletic
· Based on psbA, psbE, and matK (chloroplast) genes, P. mariniana individuals from Oahu (HL, MCT, WRST) are more closely related to other species than they are to other P. mariniana populations from Oahu or other islands
· Overall, there is a lack of concordance of history of nuclear and chloroplast genome
|JP1385-JP1389||Alakai Swamp Trail||Kaua’i|
|JP1394-JP1421||Makaha Ridge Road||Kaua’i|
|MRT||Mañana Ridge Trail||Oahu|
|WRST||Wa’ahila Ridge State Trail||Oahu|
|MCT||Manoa Cliff Trail||Oahu|
|WRT||Waihe’e Ridge Trail||Maui|
|KFR||Keauohana Forest Reserve||Big Island|
Table 1. Location of Psychotria mariniana field collections.
• Use more chloroplast and nuclear genes to draw more clarity to gene tree incongruence
• Create Ecological Niche Models (ENMs) to investigate ecological factors associated with differentiated populations
• Use microsatellites, short simple repeat (SSR) regions in the genome, as an additional set of molecular markers for population genetic analysis
• Assess gene flow between populations (FST) and allele frequency and heterozygosity measures for higher resolution genetic analyses (i.e. contemporary gene flow)
I would like to thank my advisor, Dr. John Paul, and members of the Paul Lab—Nila Le, Alec Chiono, Alex Palacios, and Hayat Elqossari—for their guidance, help and support. I thank my thesis committee members, Dr. Naupaka Zimmerman and Dr. Sevan Suni. I would also like to thank field assistants Irene Kim, Brachelle Nueku, Dr. April Randle, and Josh Serrano for their help in the field. Funding for this project was graciously provided by the University of San Francisco’s Faculty Development Fund, Student Travel Fund, Biology Gift Fund, and the Whitehead Summer Research Fellowship.