Advisor(s)

Stacy Krueger-Hadfield
Charles Amsler

Committee Member(s)

Alison Sherwood
Dustin Kemp
Heather Spalding

Document Type

Dissertation

Date of Award

1-27-2026

Degree Name

Doctor of Philosophy (PhD)

School

College of Arts and Sciences

Department

Biology

Abstract

The reproductive system encompasses the relative rates of sexual versus clonal reproduction and is responsible for partitioning genetic diversity within and among populations. However, the quantification of these rates remains limited in natural populations and has primarily focused on animals and angiosperms. This knowledge gap is particularly acute among tropical macroalgae. This dissertation addresses this by focusing on the cryptogenic invader Chondria tumulosa in the Papahānaumokuākea Marine National Monument and the invasive species Acanthophora spicifera across the Hawaiian Archipelago, Australia, and Guam. For Chondria we developed nine microsatellite loci and found a dominance of tetrasporophytes, high clonal rates, and strong temporal and spatial structure with isolation by distance. Combined, these findings suggest that C. tumulosa thalli were introduced to the PMNM, possibly via marine debris. Nine microsatellite loci were also developed for A. spicifera. In Chapter 3, we found that sites on Oʻahu and Hawaiʻi Island, had a tetrasporophytic bias while Kuaihelani was composed of both gametophytes and tetrasporophytes. Thallus fragmentation is common across all sites sampled, but there was genetic evidence of sexual reproduction. There was ongoing gene flow between Oʻahu and Hawaiʻi Island, and Kuaihelani thalli were genetically similar to thalli on Oʻahu suggesting sites on Oʻahu were a more likely source to Kuaihelani. Finally, in Chapter 4 we found that A. spicifera from Guam shared greater genetic similarity with the Main Hawaiian Islands, specifically Oʻahu, supporting accounts of the initial introduction of A. spicifera. Patterns of gene flow among the sites in the Main Hawaiian Islands were consistent with known dispersal barriers. This study provides evidence supporting the introduction of A. spicifera from Guam to Oʻahu, with subsequent spread throughout the Main Hawaiian Islands. This dissertation adds to the growing body of literature that quantifies the reproductive mode of haploid-diploid macroalgae and includes some of the only studies to assess macroalgal connectivity between the Main Hawaiian Islands and the Northwestern Hawaiian Islands.

Keywords

evolutionary ecology;invasion;Northwestern Hawaiian Islands;population genetics;seaweed

ProQuest Publication Number

32278362

ISBN

9798273380882

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