Advisor(s)
Stacy Krueger-Hadfield
Charles Amsler
Committee Member(s)
Ken Marion
Michael Sandel
Morgan Vis
Peggy Biga
School
College of Arts and Sciences
Document Type
Dissertation
Department (new version)
Biology
Date of Award
1-6-2025
Abstract
Reproductive systems describe the relative rates of sexual versus asexual reproduction and selfing versus outcrossing, governing the transmission of genetic diversity between generations and shaping evolutionary responses to environmental change. Though sex has inherent costs, it contributes to the reproductive system for most eukaryotes, generating incredible life cycle diversity. Life cycles are expected to be correlated with different reproductive systems. Diploid life cycles should be associated with outcrossing, whereas life cycles with a long-lived haploid phase are hypothesized to be associated with selfing and asexual reproduction. To test this hypothesis, we used ten polymorphic microsatellite loci to genotype 311 gametophytes from the obligately hermaphroditic haploid-diploid freshwater red alga Batrachospermum gelatinosum. Population genetic patterns indicated intragametophytic selfing, but we did not detect environmental drivers of these patterns. To improve our understanding of the temporal component of reproductive systems, we genotyped 191 B. gelatinosum gametophytes from four sites at multiple time points within and among years. Intra-annual data suggest that the seasonality of the life cycle causes shifts in gametophytic genotypes present within a year. Inter-annual data suggest that the reproductive system remains stable through time. We need to develop new population genetic tools to quantify the reproductive system through temporal genotyping. To build upon our findings about the reproductive system of the monoicous species B. gelatinosum, we developed 16 polymorphic microsatellite loci to characterize the reproductive systems and genetic structure of three Sheathia species that each exhibit intra-specific variation in hermaphroditism versus separate sexes. Our data suggest that S. americana is likely highly outcrossing, S. grandis is likely highly uniparental, and S. involuta likely has a mixed reproductive system with variation among sites. Additionally, we observed that the reproductive systems and low dispersal capabilities of these species likely shaped strong population genetic structure, with limited connectivity that may be driven by occasional events of long-distance dispersal. Overall, these data improve our knowledge of how the haploid-diploid life cycle and sexual system diversity drove the evolution of reproductive system variation in freshwater red algae. Together, these data contribute to our understanding of the evolution of sex broadly across eukaryotic life.
ProQuest ID
Recommended Citation
Connelly, Sarah, "The Evolutionary Ecology Of Reproductive System Variation In Haploid-Diploid Freshwater Red Macroalgae" (2025). All ETDs from UAB. 7263.
https://digitalcommons.library.uab.edu/etd-collection/7263
