Doctoral Dissertation Research: The Pattern and Mode of Speciation in the Hawaiian Archipelago

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The study of island biota has been central to the development of biogeography and evolutionary biology as modern disciplines. Prior to Darwin, 19th century naturalist-explorers of the Pacific Basin simply catalogued the pattern of the distribution of flora and fauna. It was not until the theory of descent with modification that the process responsible for the diversity within and among islands was described. The study of island biota continues to play a major role in the understanding of evolutionary processes, particularly with regard to the process of speciation. Traditionally, speciation is thought to be a gradual process whereby two populations split by a geographic barrier accumulate differences over time. Theories of speciation based on founder events have suggested, however, that speciation can proceed much more rapidly than with the traditional model. The gene complexes present in the parental species presumably become disrupted due to the random sampling and small number of founders. Because of the breakup of gene complexes, many novel gene combinations may be present soon after the founder event as the population grows. As selection acts on the growing population, a novel gene complex will form in the founding population, resulting in the creation of a new species. Founder-mediated speciation may be the dominant mode of speciation within oceanic island groups owing to their isolated nature. Previous efforts to find molecular genetic evidence supporting founder-event speciation models have been hampered by the limited number of loci that common genetic markers generated and by standard population genetic statistics, which were designed to describe gross genetic similarity among populations and not the nuances predicted by founder-effect models. This doctoral dissertation research project will examine speciation in a small lineage of perennial herbs endemic to the Hawaiian islands, Lipochaeta section Aphanopappus. Patterns of genetic diversity will be examined with the DNA technique of amplified fragment-length polymorphisms (AFLPs), which can generate an order of magnitude greater number of genetic markers than previously used techniques. The doctoral candidate will examine evolutionary relationships among species to determine patterns of speciation in the islands, quantify genetic diversity within and among species, and examine patterns of genetic diversity for changes in gene complexes associated with speciation events. For the latter analysis, she will use a statistical approach novel to the analysis of genetic data. This project will provide basic information about genetic diversity that will enhance biogeographic theory. The results also will be valuable for the management of endangered species within the group and may yield insights applicable to the management of other endangered Hawaiian biota. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.