Date of Award

8-2014

Level of Access Assigned by Author

Campus-Only Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ecology and Environmental Sciences

Advisor

Christopher S. Campbell

Second Committee Member

Seanna L. Annis

Third Committee Member

Peter Del Tredici

Abstract

This research contributes to the understanding of the evolutionary history of Pinaceae (the Pine family) on multiple taxonomic levels using phylogenetic systematics. Pinaceae are composed of 11 genera and 225 species. The pine family is one of the most ecologically and economically important groups of living plants, and yet much remains unknown about its origin and phylogeny.

Pinaceae have long been recognized as a natural group, having several shared derived character states, but their subfamily relationships remain controversial. In the fossil record, specimens of Pinus have been definitively identified from the lower Cretaceous, giving the family a 100-million-year history. This ancient family has no known, close living relatives, and relationships of Pinaceae to possible extinct relatives remain enigmatic. The cryptic and incomplete nature of the fossil record and lack of close living relatives greatly complicate elucidation of Pinaceae evolutionary history. In terms of taxonomic diversity, Pinaceae have the largest species richness of all gymnosperm families. Differing taxonomic treatments place the total number of gymnosperm species at 700-900, including 220-250 species of Pinaceae.

This dissertation research comprises three chapters that address phylogeny at several different levels. The first chapter focuses on the position of Cedrus within Pinaceae and addresses the deep roots of the family and the branching order of the eleven genera. To resolve the controversial subfamily classification of Pinaceae, DNA-sequence data were analyzed for nuclear phytochrome P (PHYP) and the whole chloroplast genome (plastome), and the utility of morphology was assessed. Based on molecular and phenotypic data I propose a revision to the subfamily classification to divide Pinaceae into two subfamilies: Abietoideae (Abies, Cedrus, Keteleeria, Nothotsuga, Pseudolarix, and Tsuga; Frankis 1988) and Pinoideae (Pilger 1926) which I emend to include Cathaya, Larix, Picea, and Pseudotsuga, in addition to Pinus. Secondly, the hemlocks from Ulleung Island in Korea are evaluated to assess their distinctiveness. The Ulleung hemlocks are delineated as a species (Tsuga ulleungensis, present study) using morphology, ecology, and nuclear and plastome-sequence data. The third chapter focuses on the intrageneric phylogeny of Abies. This large, complex, and understudied genus was analyzed using nuclear and plastome DNA sequences, as well as morphology. Previous subgeneric classifications of Abies have recognized between eight and eleven sections, largely on the basis of morphology. My molecular phylogenies support a greatly simplified classification of Abies with only five sections.

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