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Behavioral and nutritional regulation of colony growth in the desert leafcutter ant Acromyrmex versicolor

Description
Like individual organisms, complex social groups are able to maintain predictable trajectories of growth, from initial colony foundation to mature reproductively capable units. They do so while simultaneously responding flexibly to variation in nutrient availability and intake. Leafcutter ant colonies function as tri-trophic systems, in which the ants harvest vegetation…

Like individual organisms, complex social groups are able to maintain predictable trajectories of growth, from initial colony foundation to mature reproductively capable units. They do so while simultaneously responding flexibly to variation in nutrient availability and intake. Leafcutter ant colonies function as tri-trophic systems, in which the ants harvest vegetation to grow a fungus that, in turn, serves as food for the colony. Fungal growth rates and colony worker production are interdependent, regulated by nutritional and behavioral feedbacks. Fungal growth and quality are directly affected by worker foraging decisions, while worker production is, in turn, dependent on the amount and condition of the fungus. In this dissertation, I first characterized the growth relationship between the workers and the fungus of the desert leafcutter ant Acromyrmex versicolor during early stages of colony development, from colony foundation by groups of queens through the beginnings of exponential growth. I found that this relationship undergoes a period of slow growth and instability when workers first emerge, and then becomes allometrically positive. I then evaluated how mass and element ratios of resources collected by the ants are translated into fungus and worker population growth, and refuse, finding that colony digestive efficiency is comparable to digestive efficiencies of other herbivorous insects and ruminants. To test how colonies behaviorally respond to perturbations of the fungus garden, I quantified activity levels and task performance of workers in colonies with either supplemented or diminished fungus gardens, and found that colonies adjusted activity and task allocation in response to the fungus garden size. Finally, to identify possible forms of nutrient limitation, I measured how colony performance was affected by changes in the relative amounts of carbohydrates, protein, and phosphorus available in the resources used to grow the fungus garden. From this experiment, I concluded that colony growth is primarily carbohydrate-limited.
ContributorsClark, Rebecca, 1981- (Author) / Fewell, Jennifer H (Thesis advisor) / Mueller, Ulrich (Committee member) / Liebig, Juergen (Committee member) / Elser, James (Committee member) / Harrison, Jon (Committee member) / Arizona State University (Publisher)
Created2011

The Agassiz’s Desert Tortoise Genome Provides a Resource for the Conservation of a Threatened Species

Description

Agassiz’s desert tortoise (Gopherus agassizii) is a long-lived species native to the Mojave Desert and is listed as threatened under the US Endangered Species Act. To aid conservation efforts for preserving the genetic diversity of this species, we generated a whole genome reference sequence with an annotation based on dee…

Agassiz’s desert tortoise (Gopherus agassizii) is a long-lived species native to the Mojave Desert and is listed as threatened under the US Endangered Species Act. To aid conservation efforts for preserving the genetic diversity of this species, we generated a whole genome reference sequence with an annotation based on deep transcriptome sequences of adult skeletal muscle, lung, brain, and blood. The draft genome assembly for G. agassizii has a scaffold N50 length of 252 kbp and a total length of 2.4 Gbp. Genome annotation reveals 20,172 protein-coding genes in the G. agassizii assembly, and that gene structure is more similar to chicken than other turtles. We provide a series of comparative analyses demonstrating (1) that turtles are among the slowest-evolving genome-enabled reptiles, (2) amino acid changes in genes controlling desert tortoise traits such as shell development, longevity and osmoregulation, and (3) fixed variants across the Gopherus species complex in genes related to desert adaptations, including circadian rhythm and innate immune response. This G. agassizii genome reference and annotation is the first such resource for any tortoise, and will serve as a foundation for future analysis of the genetic basis of adaptations to the desert environment, allow for investigation into genomic factors affecting tortoise health, disease and longevity, and serve as a valuable resource for additional studies in this species complex.

Data Availability: All genomic and transcriptomic sequence files are available from the NIH-NCBI BioProject database (accession numbers PRJNA352725, PRJNA352726, and PRJNA281763). All genome assembly, transcriptome assembly, predicted protein, transcript, genome annotation, repeatmasker, phylogenetic trees, .vcf and GO enrichment files are available on Harvard Dataverse (doi:10.7910/DVN/EH2S9K).
ContributorsTollis, Marc (Author) / DeNardo, Dale F (Author) / Cornelius, John A (Author) / Dolby, Greer A (Author) / Edwards, Taylor (Author) / Henen, Brian T. (Author) / Karl, Alice E. (Author) / Murphy, Robert W. (Author) / Kusumi, Kenro (Author)
Created2017-05-31
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New Sonoran: A Graphic Novel

Description
In the event of a climate disaster, everything changes, but the places we’ve romanticized as a frontier will become new to us once again. New Sonoran is, in essence, an American story on a global problem. It draws on American pioneer/Old West/cowboy culture, the lasting effects of climate change denial,…

In the event of a climate disaster, everything changes, but the places we’ve romanticized as a frontier will become new to us once again. New Sonoran is, in essence, an American story on a global problem. It draws on American pioneer/Old West/cowboy culture, the lasting effects of climate change denial, and the individualism that pervades American culture. I want to use this project to underscore the actual isolation of individualism, as well as create a new story that speaks to a problematic but evocative cultural history while accessing an uncertain future. For this project, I drew from a varied palette of media: comics, video games, and the pervasive cultural malaise that surrounds my current generation.
The work is based in anxieties, but its media influences are a strong indicator of tone and concept. At the very least, they helped me articulate why I wanted to work on a graphic novel on a post-climate change Sonoran. This desert that I’ve grown used to will change irrevocably, but it will be a new frontier to explore while the old will become a loss to mourn. This cycle of change is something I want to highlight in my work: we can worry, mourn, and fear, but there’s going to be something new.
New Sonoran is a graphic novel based upon the journey of Sage, a cartographer and anthropologist who travels the desert, annotating maps and studying a desert irrevocably affected by global climate change. As she catalogues the changes and losses in this new landscape, she learns how residents have adapted, and how people may still relate to the land.
ContributorsBarbee, Amelia Bernadette (Author) / Soares, Rebecca (Thesis director) / Schmidt, Peter (Committee member) / Department of English (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2020-05