BRC-BIO: Maintenance of Alternative Reproductive Tactics in a Plethodontid Salamander

Understanding how variation is maintained in populations is of fundamental importance in ecology and evolutionary biology. Alternative reproductive tactics are discrete differences in reproductive behavior found within a single population, and they are often accompanied by variation in reproductive morphology. One example is illustrated by the “searching” and “guarding” males found in some species of the two-lined salamanders, a group of semi-aquatic, lungless salamanders that are widespread and abundant in the eastern United States.

This project focuses on understanding the biotic and abiotic mechanisms responsible for maintaining this polymorphism in urban streams in metro Atlanta. Through data collected from field sampling, genomic sequencing, and behavioral trials, this project will evaluate the roles of natural environmental heterogeneity, anthropogenic landscape changes, and sperm competition in the long-term coexistence of reproductive variation in these amphibians.

These results will contribute to a more general understanding of the maintenance of genotypic and phenotypic diversity in populations. Furthermore, this award will create 12 paid undergraduate research positions and allow 45 undergraduate students to engage in authentic, inquiry-driven research through a Team Research course at Kennesaw State University.

This project takes advantage of a new and tractable system to study the evolutionary maintenance of fixed, morphologically distinct, and genetically determined alternative reproductive tactics in wild populations. With undergraduate students, PI Pierson will develop and use genotyping assays to characterize the frequency of alternative reproductive tactics in two-lined salamanders and will collect paired environmental data from dozens of streams in metro Atlanta.

They will then evaluate relationships between tactic frequencies and natural and anthropogenic landscape features to contribute to broader theory focused on the role of environmental heterogeneity in the maintenance of polymorphisms. Next, PI Pierson and undergraduate students will develop and use a new genomic assay to determine paternity of clutches laid following courtship trials.

They will then use these data to evaluate evidence for multiple paternity, tactic-specific sperm competition advantages, and first- or last-male sperm precedence, which will inform more general ideas about how temporal variation in reproductive opportunities contributes to the maintenance of variation in reproductive behaviors.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.