Date of Award

2021-08-01

Degree Name

Master of Science

Department

Biological Sciences

Advisor(s)

Philip Lavretsky

Abstract

Determining a species’ ecological needs, assessing the quality of their habitat, and determining genetic differentiation and connectivity among populations is essential to their conservation. My dissertation focuses on obtaining such a holistic view for a population of Pacific Black Ducks recently established on the Island of Aunu’u, American Samoa. Specifically, I present the first evaluation of the ecology and habitat of a recently established population of Pacific Black Ducks on the Island of Aunu’u, American Samoa, in Chapter 1, while I assess the genetic connectivity and relationship of this population to other Mallard-like ducks found in Greater Indonesia, Oceania, and the Philippines in Chapter 2.

In Chapter 1, I used and optimized a variety of sampling methods to assess habitat quality and macroinvertebrate communities, as well as used GPS PTT technology to track movement of Pacific Black Ducks across three waterbodies found on the Island of Aunu’u. Additionally, I conducted time-activity-budgets that helped understand the daily life-cycle of these ducks. First, I recovered uncharacteristic behaviors compared to other Pacific Black Ducks found elsewhere, including asynchronous mating displays, brood rearing, and copulation, suggesting this population now has the capacity for year-long reproduction. More interestingly, I detected unique feeding behaviors, including hunting and consumption of introduced Tilapia present in Pala Lake; which I posit may be an adaptive response to the island’s limited resources. Finally, movement data demarcated that Pacific Black Ducks mainly used Taro Wetland and Pala Lake, despite the more favorable environmental conditions found in Fa’imulivai Marsh. In addition to determining which sampling methods proved to be most efficient, I provide evidence that all three waterbodies remain important, and will require careful management if Pacific Black Ducks are to be sustained in American Samoa. Among these, I conclude that Pacific Black Ducks prefer Pala Lake and the agricultural Taro Wetland, which provides an opportunity to strike a balance between agricultural and wildlife needs.

In Chapter 2, I use next-generation sequencing technologies to assay thousands of nuclear ddRAD sequences and the mitochondrial COI gene across three Anas spp. Specifically, I conducted population and evolutionary genetic analyses for Pacific Black Ducks and Philippine Ducks across their respective ranges and compared these to wild and domestic lineages of the Mallard. First, not only do I provide the first ddRAD-seq nuclear assessment of the endangered Philippine Duck, but report that they do not represent a hybrid species as once thought and are not currently threatened by genetic extinction from hybridization with Mallards (wild or domestic). Instead, I conclude that the relatively lower levels of genetic diversity may hinder this species ability to adapt in the future and is an important consideration in future conservation efforts. For Pacific Black Ducks, I find that (1) Pacific Black Ducks from Australia, Timor-Leste in Indonesia, Papua New Guinea, Tasmania, and Aunu’u Island in American Samoa, represent A. s. rogersi, (2) New Zealand ducks represents A. s. superciliosa as expected, and (3) Lesser Grey Ducks from the Solomon Islands represent A. s. pelewensis. Importantly, although I predictably recovered samples assigning to A. s. rogersi and A. s. superciliosa, only one population within the predicted range assigned to A. s. pelewensis. Specifically, Aunu’u island in American Samoa is within the predicted range of A. s. pelewensis, however, I provide evidence that these Pacific Black Ducks are A. s. rogersi. Like Philippine Ducks, I concluded that the conservation threat to Pacific Black Ducks from Aunu’u, American Samoa, and the Solomon Islands is likely their relatively low genetic diversity that decrease their adaptive responses to future ecological changes. Conversely, I concluded that the conservation of Pacific Black Ducks on Australia, New Zealand, and Timor-Leste in Indonesia appears to be threatened due to introgressive hybridization from local Mallards.

By taking such an interdisciplinary approach, I was able to describe the availability and quality of remaining habitat, establish interesting behavioral aspects, as well as shed light into the evolutionary history and biogeographical connectivity of the recently established Pacific Black Duck population in Aunu’u, American Samoa, as compared to other Mallard-like ducks in Oceania, Greater Indonesia, and the Philippines. These data will undoubtedly help shape discussions surrounding taxonomy and range distributions of Pacific Black Ducks, in general, while directly impacting future conservation decisions of the localized population of Pacific Black Ducks of Aunu’u, American Samoa.

Language

en

Provenance

Received from ProQuest

File Size

114 p.

File Format

application/pdf

Rights Holder

Marissa Kaminski

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