DIVERSITY AND ABUNDANCE OF FLEAS ON RICHARDSON’S GROUND SQUIRRELS AND IN THEIR BURROWS, AND THE BACTERIA WITHIN THE MICROBIOMES OF THESE FLEAS

The diversity and abundance of parasites among a host population varies across time and space. Parasites are restricted in an ecosystem by the range of hosts they infest (= the degree of host specificity), by the interactions with other parasites, environmental conditions, and the fitness of the host they parasitize. Some parasites are vectors of pathogens that affect wildlife, domestic animals and/or humans. For example, Yersinia pestis, the causative agent of plague, is transmitted from infected animals to susceptible animals by a variety of flea species. Black-tailed prairie dogs (Cynomys ludovicianus), a threatened species in North America, are highly susceptible to Y. pestis infection. They share multiple species of flea that are vectors of Y. pestis with Richardson's ground squirrels (Urocitellus richardsonii) and they co-exist in Grasslands National Park in southern Saskatchewan, Canada. Although work has been conducted previously on flea communities associated with black-tailed prairie dogs, little research has been conducted on fleas of U. richardsonii, particularly for populations located in their northern parts of the distributional range. Knowledge of the diversity and abundance of fleas parasitizing U. richardsonii and of the bacteria in flea microbiomes is imperative for understanding the risk and disease transmission to U. richardsonii and C. ludovicianus. In this thesis, I investigate the bacterial communities of the different flea species parasitizing Richardson's ground squirrels and assess if ecological concepts (e.g. host specificity, community structure) that apply to parasites on hosts can be applied to the bacterial of these fleas. The first objective was to determine the species of fleas using genetic markers because of the difficulties distinguishing among species based on morphological characters. Also, this approach eliminated the need to chemical clear the internal structures and bloodmeal, permitting molecular-based studies of the fleas and their microbiomes. I assessed the suitability of five molecular targets, the nuclear 18S ribosomal RNA (rRNA) and 28S rRNA genes, the nuclear internal transcribed spacer 2 (ITS2), and the mitochondrial cytochrome oxidase c subunit 1 and 2 genes (cox1 and cox2), to identify eleven flea species parasitizing Richardson's ground squirrels. The ITS2 and 28S rRNA gene were the best genetic markers for species identification, while cox2 was more useful for studying the population genetics of fleas. The second objective was to investigate the community structure of fleas on U. richardsonii in Alberta and Saskatchewan. The dominant species on U. richardsonii near Lethbridge (Alberta) was Oropsylla rupestris, while O. tuberculata was the most abundant species on U. richardsonii near Moose Jaw (Saskatchewan). The sex and length of the host species as well as the month of collection were factors that significantly influenced the prevalence and abundance of fleas parasitizing Richardson's ground squirrels. Differences were also detected in the diversity and relative abundance of fleas in the burrows of U. richardsonii at a rural site (near Bradwell) and an urban site (Saskatoon). The most prominent species in the urban site was O. rupestris, while O. bruneri was the most prominent species at the rural site. Seasonal patterns of activity were observed with flea species peaking during different months. I also investigated the prevalence and abundance of Bartonella, Rickettsia, and Wolbachia in the bacterial communities of nine species of fleas from the burrows of Richardson's ground squirrels in Saskatchewan. I found that the bacterial load of these samples and the prevalence of key bacterial species (e.g., Bartonella, Rickettsia, and Wolbachia) was very low based on qPCR analysis. A conventional PCR approach was taken to determine the diversity and abundance of Bartonella, Rickettsia, and Wolbachia in these samples. Distinct strains of Wolbachia were detected in different species of flea species and multiple strains of Bartonella washoensis were detected in O. bruneri. Three species of Oropsylla and Neopsylla inopina contained a Rickettsia-like endosymbiont which have not been previously reported in fleas. Further investigation is required into the role and frequency of Wolbachia and Rickettsia-like endosymbiont in fleas. These findings provide insight into the diversity of fleas on Richardson's ground squirrels at their northern distribution and a framework for investigating the bacterial communities of these fleas.

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