Date of Award
Spring 5-4-2023
Degree Type
Thesis
Degree Name
Master of Science in Integrative Biology (MSIB)
Department
Biology
Committee Chair/First Advisor
Clint Penick
Major Professor
Todd Pierson
Second Committee Member
Thomas McElroy
Abstract
Alternative reproductive tactics (ARTs) refer to discrete variation in reproductive behavior between members of a sex and within a species. ARTs are present in Blue Ridge two-lined salamanders (Eurcyea cf. wilderae) in the form of male polymorphism. Two male morphs exist: “searching” males and “guarding” males. Each phenotype has a unique reproductive ecology and associated discrete morphological differences. Another trait that shows discrete variation in E. cf. wilderae is the larval period, which may be one or two years in length. This thesis explores the proximate causes of ARTs in a population of E. cf. wilderae from the Blue Ridge of North Carolina. The first chapter of this thesis surveys for a genetic cause for these ARTs. In this chapter, I use genomic data to evaluate population structure, identify sex-linked and ART-linked genetic markers, and estimate effective population size and kinship. The results suggest that E. cf. wilderae follow an XY sex determination system wherein alternative haplotypes of the Y chromosome determine male ARTs. The effective population size was found to be consistent with estimates from other studies on closely related taxa and the kinship coefficients within the sample were found to be low. The second chapter of this thesis assesses the relationship between ARTs and the length of the larval period, another axis of discrete life history variation in E. cf. wilderae. In this chapter, I use the ART-specific genetic markers identified in the first chapter to identify the reproductive phenotypes of 200 larvae belonging to two age classes and calculate the relative frequencies of phenotypes within the population. The results suggest no relationship between ARTs and larval period. However, I found an even sex ratio and that searching males are almost twice as abundant as guarding males in the population. Overall, this thesis not only contributes to the body of knowledge on genetically determined ARTs and the evolutionary ecology of E. cf. wilderae by: 1) identifying an XY sex determination system; 2) identifying that ARTs are linked to alternative Y chromosome haplotypes; and 3) demonstrating that larval period is not associated with ARTs; but also addresses broader topics such as: 1) the causes of alternative phenotypes with discrete life history differences; 2) the genomic bases of polymorphism and sex determination in species; and 3) the relationship between genotype, phenotype, and environmental factors.