Date of Award

2026-05-01

Degree Name

Master of Science

Department

Biological Sciences

Advisor(s)

Philip Lavretsky

Abstract

Domestication is a process in which wild populations are morphologically and/or behaviorally manipulated through selective breeding to become optimized for living in captivity. Consequently, many traits become quickly and significantly diverged from their ancestral, wild lineages, a process known as part of domestication syndrome. Captive breeding of mallards (Anas platyrhynchos) was one of the last major successful domestication events resulting in dozens of recognized breeds today. Many breeds were optimized for either ornamental or agricultural purposes (i.e., meat and/or egg production), but the game-farm mallard was specifically bred for sport hunting. In North America, the use of game-farm mallards to supplement huntable populations of mallards has been a known practice since the 1920s. Landscape genomics studies have negated the notion that their presence on the landscape has no effect on wild populations, uncovering that the release of game-farm mallards has resulted in wide-spread hybridization, with eastern mallard populations now largely characterized as a wild x game-farm mallard hybrid swarm. Indeed, regions where stocking has been pronounced have also experienced substantial declines in their wild mallard populations. However, the biological consequences of interbreeding between wild and game-farm mallards are yet to be fully understood. Specifically, despite recent behavioral studies scaling significant differences in migration and habitat utilization with the amount of game-farm mallard ancestry an individual carries, the underlying mechanisms as to the cause of these differences remain unknown. Here, I attempt to further understand whether physiological and/or molecular differences in mitochondrial variation may explain known behavioral differences between wild mallards, game-farm mallards, and wild game-farm mallard hybrids. Migratory behavior requires significant amounts of energy, and if game-farm mallards significantly differ from their wild counterpart in either the molecular or fat composition due to the domestication process, then I predict that the transfer of such traits via gene flow can have negative effects on the viability of wild populations. Towards this, I attempted the first deployment of Dual Energy X-Ray Absorptiometry (DXA) technology to assess body composition. In Chapter 1, I report the only significant difference recovered was total mass between male game-farm and hybrid mallards, as well as between female wild and game-farm mallards. I note that a lack of sample effort likely resulted in non-significant tests, and demonstrate that the proportion of fat, lean mass, as well as bone mineral content present showed notable differences, including how they scaled with total body mass. Regardless, I demonstrate that the capacity to increase to sufficient sample sizes given my reported mean differences in physiological parameters can be readily achieved with DXA technology. Next, I assessed whether molecular differences across the mitogenome existed, and whether mutations result in significant protein changes. In short, the mitogenome is critical for energy production of any organism, and mutations that result in less efficient ATP or NADH synthesis is expected to result in a reduction for long distance migratory behavior. In mallards, there are two distinct haplogroups that diverged 500,000 years ago and ascribed to mallards from Eurasia (i.e., Old World A) or North America (i.e., New World B). All game-farm mallards carry OW A haplotypes because of their domestication in 1630s England, and with studies confirming that >90% of OW A haplotypes found in North America are the result of introgression from released game-farm mallards. Given that energetic demands are low in captive settings, mutations resulting in reduced efficiency of genes on the mitogenome is possible. However, I do not find an elevated signatures of non-synonymous mutations in Old World A haplotypes but do report that protein coding genes of New World B haplotypes were under stricter purifying selection in Chapter 2. Together, although physiological and mitogenomic differences exist between wild and game-farm mallards, they were not as prominent as initially predicted. Future research efforts will benefit from attempting similar studies of mallards representing the ancestry spectrum but existing in the wild.

Language

en

Provenance

Received from ProQuest

File Size

61 p.

File Format

application/pdf

Rights Holder

Nicholas Enriquez

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Biology Commons

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