overall dynamics of the system and how they depend on the incidence
function. I consider both an epidemic and endemic perspective of the
model, but in both cases, three classes of incidence
functions are identified.
In the epidemic form,
power incidences, where the infective portion $I^p$ has $p\in(0,1)$,
cause unconditional host extinction,
homogeneous incidences have host extinction for certain parameter constellations and
host survival for others, and upper density-dependent incidences
never cause host extinction. The case of non-extinction in upper
density-dependent
incidences extends to the case where a latent period is included.
Using data from experiments with rhanavirus and salamanders,
maximum likelihood estimates are applied to the data.
With these estimates,
I generate the corrected Akaike information criteria, which
reward a low likelihood and punish the use of more parameters.
This generates the Akaike weight, which is used to fit
parameters to the data, and determine which incidence functions
fit the data the best.
From an endemic perspective, I observe
that power incidences cause initial condition dependent host extinction for
some parameter constellations and global stability for others,
homogeneous incidences have host extinction for certain parameter constellations and
host survival for others, and upper density-dependent incidences
never cause host extinction.
The dynamics when the incidence function is homogeneous are deeply explored.
I expand the endemic considerations in the homogeneous case
by adding a predator into the model.
Using persistence theory, I show the conditions for the persistence of each of the
predator, prey, and parasite species. Potential dynamics of the system include parasite mediated
persistence of the predator, survival of the ecosystem at high initial predator levels and
ecosystem collapse at low initial predator levels, persistence of all three species, and much more.
Today, some modern zoos, aquariums, and similar animal-exhibiting institutions continue to shift their priorities toward a focus on the conservation of wildlife. Conservation challenges span a broad subject area. The focus that any institution chooses can vary greatly in terms of magnitude and measures of significance. Many modern zoos often choose to make global conservation a central institutional priority: conservation of biodiversity, habitat protection, species extinction, and more. Some institutions, however, set conservation priorities on a smaller scale, focusing on contributions that have a more indirect effect on wild species and habitats, such as the welfare of populations in captivity, raising public awareness of conservation missions, and conservation education. By comparing the institutional priorities of two organizations within the Association of Zoos and Aquariums (AZA), the Arizona-Sonora Desert Museum and the Phoenix Zoo, I explore how each institution manages its living collections and works toward its respective conservation mission. I interviewed members of each institution and analyzed the similarities and differences between the organizations based on their management of living collections, and how different mission statements might shape their work. This included investigating the focus each institution has on animal welfare, in situ and ex situ conservation, and maintaining public interest. This also required defining what conservation and welfare mean to each institution and how that affects the management of their living collections. From a literature review and interviews with representatives from each institution, I was able to determine that despite any differences in style or in the language of respective mission statements, each institution prioritizes connecting the public and conservation of biodiversity. While they employ different approaches - one institution takes a regional interest in the Sonoran Desert ecosystem and landscape; the other takes a more global approach to its experiences, exhibits, and collections - the core values and ultimately the vision remain the same. Conservation may serve as the primary motivator for both the Museum and the Zoo, but my thesis is that this rationale could not be realized by itself for these institutions. Rather, conservation as a core value relies upon the support of other critical institutional priorities working together. In this way animal welfare, public engagement, and conservation relate to one another as institutional values and create the impact that the zoo and museum have on their local communities, as well as on conservation as a whole.
As zoos’ goals, designers’ values, and guests’ expectations change, so do the structures seen at the zoo. Exhibit history is not clear cut, and – despite what some may claim – is not inherently linear. Exhibit strategies develop as a result of tensions, both social and operational, imposed from both inside and outside of zoos. This literature review examines the history of zoo architecture by defining six design periods and considering the lenses of race, class, and nature.
Through the application of the approach, microbiological interactions in serpentinized fluids were found to be more complex than anticipated. Serpentinized fluids are hyperalkaline and pH is often considered the driving parameter of microbial diversity, however hydrogenotrophic community composition varies in hyperalkaline fluids with similar pH. The composition of hydrogenotrophic communities in serpentinized fluids were found to correspond to the availability of the electron acceptor for hydrogenotrophic redox reactions. Specifically, hydrogenotrophic community composition transitions from being dominated by the hydrogenotrophic methanogen genus, Methanobacterium, when the concentration of sulfate is less than ~10 μm. Above ~10 μm, sulfate reducers are most abundant. Additionally, Methanobacterium was found to co-occur with the protist genus, Cyclidium, in serpentinized fluids. Species of Cyclidium are anaerobic and known to have methanogen endosymbionts. Therefore, Cyclidium may supply inorganic carbon evolved from fermentation to Methanobacterium, thereby mitigating pH dependent inorganic carbon limitation.
This approach also revealed possible biological mechanisms for methane oxidation in Yellowstone hot springs. Measurable rates of biological methane oxidation in hot spring sediments are likely associated with methanotrophs of the phylum, Verrucomicrobia, and the class, Alphaproteobacteria. Additionally, rates were measurable where known methanotrophs were not detected. At some of these sites, archaeal ammonia oxidizer taxa were detected. Ammonia oxidizers have been shown to be capable of methane oxidation in other systems and may be an alternative mechanism for methanotrophy in Yellowstone hot springs. At the remaining sites, uncharacterized microbial lineages may be capable of carrying out methane oxidation in Yellowstone hot springs.