Advisor(s)
Stacy Krueger-Hadfield
Charles Amsler
Committee Member(s)
James McClintock
Richard Snyder
Stephen Watts
School
College of Arts and Sciences
Document Type
Dissertation
Department (new version)
Biology
Date of Award
9-11-2025
Abstract
Haploid-diploid life cycles offer valuable insight into the evolution of sex and ploidy cycling, but empirical research has largely focused on diploid-dominant taxa, such as angiosperms. Expanding empirical studies to include a broader range of eukaryotic diversity is critical to ultimately understand responses to climate change. This dissertation addresses gaps in our understanding of macroalgal reproductive modes by examining macroalgae Gracilaria vermiculophylla and Ulva spp. along the Delmarva Peninsula. To understand how hard and soft bottom habitats have structured genetic diversity and reproductive modes in Gracilaria vermiculophylla and how these habitats have shaped colonization of this area, we used nine polymorphic microsatellite loci to genotype 1,314 thalli from six different sites from 2020 to 2023. We found that sexual reproduction prevailed in hard bottom sites, whereas asexual reproduction dominated soft bottom sites and was accompanied by tetrasporophytic dominance. Genetic diversity was structured by habitat type, then by site, and finally by year. In Chapter 2, we tested the hypothesis that herbivory may act as an ecological driver of haploid-diploid life cycle maintenance. In feeding assays, the amphipod Ampithoe valida showed a preference for male gametophytes when compared to tetrasporophytes, but female gametophyte consumption was not distinguishable from other phases. Finally, we conducted a molecular survey of 113 Ulva thalli collected across ten sites and each of the four boreal seasons along the Delmarva Peninsula using chloroplast molecular markers rbcL and tufA to better understand fine scale Ulva diversity, establishing a baseline for species composition and environmental gradients in which they are found. This dissertation highlights the importance of integrating genetic, ecological, and natural history observations to better understand the evolution and maintenance of complex life cycles.
ProQuest ID
Recommended Citation
Oetterer, Alexis, "The Eco-Evolutionary Consequences Of Spatial Patterning Of Macroalgal Life Cycle Stages And Reproductive Mode Variation" (2025). All ETDs from UAB. 7389.
https://digitalcommons.library.uab.edu/etd-collection/7389
