The Aztec empire emerged in AD 1428 as a result of the triple alliance among the city-states of Tenochtitlan, Texcoco, and Tlacopan. Although it is well documented that the Aztecs conquered numerous polities in the Basin of Mexico over the next 100 years, the demographic consequences of this expansion remain unclear. At the influential Otomi city-state of Xaltocan, for example, colonial documents suggest that the Aztec conquest led to a replacement of the original Otomi population, whereas archaeological finds suggest that a significant portion of the original population may have remained at the city under Aztec rule. To help resolve questions about Xaltocan’s population history during this period, I extracted ancient DNA from 21 individuals that can be divided into two temporal subpopulations (roughly predating and postdating the hypothesized replacement event). I determined mitochondrial DNA haplogroups through RFLP analyses and constructed haplotypes based on 372 bp of HVR1 sequence. Statistical analyses show significant differences between the mitochondrial composition of the two subpopulations. Altogether, the results of this study support the hypothesis that matrilines at Xaltocan underwent a significant replacement event following the Aztec conquest, and they suggest that the Aztec expansion may have had a substantial genetic impact on certain Mesoamerican populations. / text

A new strategy to fight mosquito-borne disease is based on infections of the maternally-transmitted, intracellular bacterium Wolbachia pipientis. Estimates predict that Wolbachia infects nearly half of all insect species, as well as other arthropods and some nematodes. Wolbachia manipulates the reproduction of its host to promote infection, most commonly causing a form of conditional sterility known as cytoplasmic incompatibility. Generally, Wolbachia infections are benign and do not inflict significant costs upon its host. However, studies demonstrate that some infections are associated with substantial costs to its host. These same infections can also induce pathogen interference and decrease vector competency of important disease vectors. Theory predicts that organisms that incur costs relative to conspecifics are less competitive and their competitive exclusion is expected. In the case of Wolbachia, the bacterium can influence reproduction such that phenotypes with lower fitness may still reach fixation in natural populations. In this dissertation, I describe theoretical and empirical experiments that aim to understand the invasion and stability of Wolbachia infections that impose costs on their host. Particular attention is paid to immature insect lifestages, which have been previously marginalized. These results are discussed in relation to ongoing vector control strategies that would use Wolbachia to manipulate vector populations. Specifically, I discuss the cost of novel Wolbachia infections in Aedespolynesiensis, which decreases larval survival and overall fitness relative to wild-type mosquitoes. Then, a theoretical framework was developed to determine the significance of reductions in larval viability in relation to the population replacement disease control strategy. Further theoretical studies determined that Wolbachia infections, once established, resist re-invasion by uninfected individuals despite relatively high costs associated with infection so long as the infection produces reproductive manipulations. Additional studies determined that larvae hatched from old eggs experience reduced survival in mosquito strains with novel Wolbachia infections when compared to the wild-type. To validate the theoretical studies, model predictions were tested empirically to determine the importance of the larval viability. Finally, a COPAS PLUS machine was evaluated and its role in understanding early larval development in mosquitoes is discussed. The importance of integrated research in disease control is highlighted.