Date of Award

Spring 1-1-2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ecology & Evolutionary Biology

First Advisor

Andrew P. Martin

Second Advisor

Nolan C. Kane

Third Advisor

Rebecca J. Safran

Fourth Advisor

Valerie J. McKenzie

Fifth Advisor

Dena M. Smith

Abstract

Minimizing inbreeding depression and maintaining genetic diversity are central goals of conservation programs, including the Greenback Recovery Program (GRP), an interagency effort to protect the lineage of trout native to the South Platte River drainage in Colorado. The last remaining population of greenback cutthroat trout consists of about 700 individuals found in a three-mile stretch of stream in the Arkansas drainage, outside its native range. The GRP is committed to reintroducing the greenback into its native range in the South Platte. To do so, they are using a hatchery stock founded by 46 wild individuals. Both wild and hatchery populations have limited genetic diversity and deformities are common in the hatchery population.

Recovering the fitness of the hatchery population of greenbacks requires variation in fitness upon which selection can act. I performed crosses between individuals to quantify any remaining variation in fitness. The population had high variation in egg production and fertilization but very little variation in overall offspring survival. This suggests that the hatchery managers should consider alternative sources of genetic diversity, such as individuals from the wild or from other subspecies.

I used a crossing experiment between greenback cutthroat trout and a related subspecies to describe the genomic patterns of recovery of fitness. When greenbacks are crossed with another subspecies, the hybrid offspring have much higher fitness than the pure greenback offspring. I found that the probability of survival has a strong genetic component and that relatedness between the parents is a strong predictor of offspring survival, with offspring from less related greenback parents having higher fitness. This research will help managers decide whether outcrossing is a viable strategy to increase genetic diversity in cutthroat trout.

I explored the barriers to implementing evolutionary restoration tools, which include a reluctance to disrupt the taxonomic integrity of species. Evolutionary restoration is analogous to ecological restoration: both fields face the challenge of choosing appropriate restoration baselines and setting realistic restoration goals. Active interventions to increase gene flow should be considered as a complement to habitat protection and ecological restoration to prevent species decline.

I developed a teaching case study based on cutthroat trout research. The case study gives upper division biology students practice in applying evolutionary concepts to a real-world conservation problem by making evidence-based decisions accounting for uncertainty in real data sets. I used the case of cutthroat trout in Colorado because it requires a fundamental understanding of evolutionary processes such as speciation and hybridization and raises questions about the value of native species and the goals of conservation efforts.

Share

COinS