Date of Graduation

Spring 5-18-2019

Document Type

Thesis

Degree Name

Master of Science in Biology

College/School

College of Arts and Sciences

Department/Program

Biology

First Advisor

Dr. John Paul

Second Advisor

Dr. Sevan Suni

Third Advisor

Dr. Naupaka Zimmerman

Abstract

Speciation is a fundamental evolutionary process that remains poorly understood. Speciation ultimately begins with population divergence, so we can elucidate the complexities of speciation by first understanding the process and drivers of population divergence. To conduct population-level analyses, ecologists and evolutionary biologists have turned to island systems, primarily for their geographic orientation and high endemism. The Hawaiian archipelago is home to over 8,700 endemic species making it a great natural laboratory to study species diversification at the population level. The Hawaiian Psychotria (kōpiko, or wild coffee) make up 11 of these species and have been used to understand colonization and divergence patterns across the islands. Previous studies found the divergence of the Hawaiian Psychotria began roughly 8.23 Ma, prior to the formation of Kauai (5.1 Ma), the oldest main island. This finding suggests that population divergence occurred on or between the atolls that are now submerged underwater. Thus, factors driving population divergence and speciation of the Hawaiian Psychotria are, to this day, unknown. To shed light on the historical and ongoing speciation processes of the Hawaiian Psychotria, I conducted a population-level analysis using a widespread plant lineage, Psychotria mariniana. Two phylogenies were inferred using nuclear (ETS and ITS) and chloroplast (psbA and psbE-petL) markers. These trees also included other species within the Hawaiian Psychotria genus and were used to trace dispersal history and assess genetic differentiation between different P. mariniana populations (intraspecific) and their congeners (interspecific). Although further research is needed to support more conclusive results, the data suggest that both inter-and intra-island genetic divergence may have played a role in historical diverging patterns of the Hawaiian Psychotria. This study showed that one of these 11 species, P. mariniana, is at the beginning stages of divergence which suggests the Hawaiian Psychotria are continuing to diverge over time.

Download

Share

COinS