Evolutionary and ecological processes in microparasite communities of bats
Date
2020
Authors
McKee, Clifton Dyer, author
Webb, Colleen T., advisor
Kosoy, Michael Y., committee member
Hayman, David T. S., committee member
Funk, W. Chris, committee member
Schountz, Tony, committee member
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Abstract
The majority of parasites infecting humans come from animals, so it is necessary to study how parasites are maintained in nature to understand which human populations are at risk of spillover. Parasites are also highly diverse in their own right, with their own fascinating ecology, so studying parasite communities will give us a full perspective of Earth's biodiversity. Research has shown that bats are significant hosts of parasites globally, including important pathogens of humans. The unique evolution of flight in bats has influenced their ability to disperse parasites, and may have modified their immune systems to be more tolerant of infections compared to other mammals. Thus, studying bat parasite communities could deepen our knowledge of the evolutionary history of mammalian parasites and the importance of flight in the maintenance of parasite community diversity in bats. In this dissertation, I focus on the evolutionary history and ecological forces affecting diversity in blood-borne microparasite communities of bats. There is a particular focus in this dissertation on Bartonella bacteria, a common parasite in mammals. To determine the importance of bats in the historical diversification of Bartonella bacteria, I performed the most comprehensive phylogenetic analysis of the genus to date, including data from 121 strains cultured from bats globally. I discovered that Bartonella bacteria began infecting mammals 62 million years ago and likely originated from bats. In a review of other bat parasites, including eukaryotic trypanosomes and haemosporidian parasites, I find that bats have had a similarly deep influence on the evolution of these taxa, and their historical spread across continents and to other mammalian hosts. To examine the importance of dispersal on parasite community diversity at smaller ecological scales, I focused on Bartonella communities in African fruit bats. I investigated differences in the Bartonella communities in fruit bat populations across a West African island chain. In addition, I examined the population genetics of bat flies, the presumed vectors of Bartonella in bats, and bat fly symbionts to compare with the genetic population structure of the bat hosts. Bartonella communities differed across islands and showed a pattern of isolation by geographic distance, indicating that dispersal of parasite species is constrained by bat movement patterns. Population structure was reduced in bat flies and symbionts compared to that of the bat hosts, suggesting that bat movements between islands are going undetected from population genetics of the hosts alone. Finally, I investigated Bartonella community dynamics in a captive colony of fruit bats in Ghana over a sampling period of three years. In this study, the population density of bat flies declined over time and was then restored via reintroduction of flies from a wild source population, causing predictable changes in Bartonella prevalence within the bat colony. These results provide the first experimental confirmation of bat flies as vectors of Bartonella in bats. In addition, changes in Bartonella diversity within the colony that occurred in the absence of bat flies might be attributed to ecological drift and selection through interspecies competition mediated by the host immune system. These projects highlight the ecological and evolutionary processes affecting microparasite communities of bats, providing useful information for understanding how parasite biodiversity is created and maintained in natural populations.
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Subject
disease ecology
Bartonella
phylogenetics
molecular genetic