Matching Items (3)
Description
Here I present a phylogeographic study of at least six reproductively isolated lineages of harvester ants within the Pogonomyrmex barbatus and P. rugosus species group. The genetic and geographic relationships within this clade are complex: four of the identified lineages are divided into two pairs, and each pair has evolved under a mutualistic system that necessitates sympatry. These paired lineages are dependent upon one another because interlineage matings within each pair are the sole source of hybrid F1 workers; these workers build and sustain the colonies, facilitating the production of the reproductive caste, which results solely from intralineage fertilizations. This system of genetic caste determination (GCD) maintains genetic isolation among these closely related lineages, while simultaneously requiring co-expansion and emigration as their distributions have changed over time. Previous studies have also demonstrated that three of the four lineages displaying this unique genetic caste determination phenotype are of hybrid origin. Thus, reconstructing the phylogenetic and geographic history of this group allows us to evaluate past insights and plan future inquiries in a more complete historical biogeographic context. Using mitochondrial DNA sequences sampled across most of the morphospecies' ranges in the U.S. and Mexico, I employed several methods of phylogenetic and DNA sequence analysis, along with comparisons to geological, biogeographic, and phylogeographic studies throughout the sampled regions. These analyses on Pogonomyrmex harvester ants reveal a complex pattern of vicariance and dispersal that is largely concordant with models of late Miocene, Pliocene, and Pleistocene range shifts among various arid-adapted taxa in North America.
ContributorsMott, Brendon (Author) / Gadau, Juergen (Thesis advisor) / Fewell, Jennifer (Committee member) / Anderson, Kirk (Committee member) / Arizona State University (Publisher)
Created2012
Description
In social insect colonies, as with individual animals, the rates of biological processes scale with body size. The remarkable explanatory power of metabolic allometry in ecology and evolutionary biology derives from the great diversity of life exhibiting a nonlinear scaling pattern in which metabolic rates are not proportional to mass, but rather exhibit a hypometric relationship with body size. While one theory suggests that the supply of energy is a major physiological constraint, an alternative theory is that the demand for energy is regulated by behavior. The central hypothesis of this dissertation research is that increases in colony size reduce the proportion of individuals actively engaged in colony labor with consequences for energetic scaling at the whole-colony level of biological organization. A combination of methods from comparative physiology and animal behavior were developed to investigate scaling relationships in laboratory-reared colonies of the seed-harvester ant, Pogonomyrmex californicus. To determine metabolic rates, flow-through respirometry made it possible to directly measure the carbon dioxide production and oxygen consumption of whole colonies. By recording video of colony behavior, for which ants were individually paint-marked for identification, it was possible to reconstruct the communication networks through which information is transmitted throughout the colony. Whole colonies of P. californicus were found to exhibit a robust hypometric allometry in which mass-specific metabolic rates decrease with increasing colony size. The distribution of walking speeds also scaled with colony size so that larger colonies were composed of relatively more inactive ants than smaller colonies. If colonies were broken into random collections of workers, metabolic rates scaled isometrically, but when entire colonies were reduced in size while retaining functionality (queens, juveniles, workers), they continued to exhibit a metabolic hypometry. The communication networks in P. californicus colonies contain a high frequency of feed-forward interaction patterns consistent with those of complex regulatory systems. Furthermore, the scaling of these communication pathways with size is a plausible mechanism for the regulation of whole-colony metabolic scaling. The continued development of a network theory approach to integrating behavior and metabolism will reveal insights into the evolution of collective animal behavior, ecological dynamics, and social cohesion.
ContributorsWaters, James S., 1983- (Author) / Harrison, Jon F. (Thesis advisor) / Quinlan, Michael C. (Committee member) / Pratt, Stephen C. (Committee member) / Fewell, Jennifer H. (Committee member) / Gadau, Juergen (Committee member) / Arizona State University (Publisher)
Created2012
Description
Wolbachia is a genus of obligately intracellular bacterial endosymbionts of arthropods and nematodes, infecting up to 66% of all such species. In order to ensure its transmission, it may modify host reproduction by inducing one of four phenotypes: cytoplasmic incompatibility, feminization of genetic males, killing of male embryos, and induction of thelytokous parthenogenesis. This investigation was a characterization of the so-far unexamined Wolbachia infection of Pogonomyrmex ants. Five main questions were addressed: whether Wolbachia infection rates vary between North and South America, whether infection rates are dependent on host range, whether Wolbachia affects the caste determination of P. barbatus, whether infection rates in Pogonomyrmex are similar to those of other ants, and whether Wolbachia phylogeny parallels the phylogeny of its Pogonomyrmex hosts. Using PCR amplification of the wsp, ftsZ, and gatB loci, Wolbachia infections were detected in four of fifteen Pogonomyrmex species (26.7%), providing the first known evidence of Wolbachia infection in this genus. All infected species were from South America, specifically Argentina. Therefore, Wolbachia has no role in the caste determination of the North American species P. barbatus. Additionally, while it appears that the incidence of Wolbachia in Pogonomyrmex may be limited to South America, host range did not correlate with infection status. The incidence of Wolbachia in Pogonomyrmex as a whole was similar to that of invasive Solenopsis and Linepithema species, but not to Wasmannia auropunctata or Anoplolepis gracilipes, which retain Wolbachia infection in non-native locations. This suggests that there may be a parallel in Wolbachia infection spread in certain short-term models of species colonization and long-term models of genus radiation. Finally, there was no congruity between host and parasite phylogeny according to maximum likelihood analyses, necessarily due to horizontal transfer of Wolbachia between hosts and lateral gene transfer between Wolbachia strains within hosts.
ContributorsHarris, Alexandre Marm (Author) / Gadau, Juergen (Thesis director) / Martin, Thomas (Committee member) / Helmkampf, Martin Erik (Committee member) / Barrett, The Honors College (Contributor) / Computer Science and Engineering Program (Contributor) / School of Life Sciences (Contributor)
Created2014-05