Browsing by Subject "Ants"
Now showing 1 - 7 of 7
Results Per Page
Sort Options
Item A faunistic survey of the organisms associated with ant colonies of West Texas (especially Solenopsis spp.)(Texas Tech University, 1980-12) Neece, Kenneth CharlesNot availableItem Ant genotype, not fungus genotype, predicts aggression in the asexual fungus-farming ant, Mycocepurus smithii(2015-08) Barrett, Brian Timothy; Kirkpatrick, Mark, 1956-; Mueller, Ulrich GHamilton's rule specifies that the relatedness of two individuals will have a large bearing on whether an altruistic action is performed; however, it says little with regards to whether individuals are able to discern that relatedness. In this study we examine whether the fungus-farming ant Mycocepurus smithii uses genotypic information to decide whether to attack an introduced queen or if it utilizes environmental cues from the fungus that they cultivate. We performed 180 blind trials in which we introduced queens to queenless mesocosms and recorded and scored aggression behavior directed towards the queen. We find strong evidence that M. smithii uses genotype to mediate aggression, but find no support that fungal cultivar plays any role in recognition. These results serve to support Hamilton's notion that relatedness acts as a gateway to altruism.Item Diversity and evolution of reproductive systems in Mycocepurus fungus-growing ants(2010-05) Rabeling, Christian; Mueller, Ulrich G.; Hillis, David M.; Bolnick, Daniel I.; Schultz, Theodore R.; Singer, Michael C.The general prevalence of sexual reproduction over asexual reproduction among metazoans testifies to the evolutionary, long-term benefits of genetic recombination. Despite the benefits of genetic recombination under sexual reproduction, asexual organisms sporadically occur throughout the tree of life, and a few asexual lineages persisted over significant evolutionary time without apparent recombination. The study of asexual organisms therefore may provide clues to answer why almost all eukaryotes reproduce via meiosis and syngamy and why asexual eukaryotes are almost always evolutionarily short-lived. Towards understanding the evolution of asexual lineages in the Hymenoptera, I first review the diversity of reproductive systems in the Hymenoptera, introduce the study organism, the fungus-gardening ant Mycocepurus smithii, and discuss my research objectives. Second, I integrate information from reproductive physiology, reproductive morphology, natural history and behavior, to document that that queens of M. smithii are capable of thelytokous parthenogenesis, workers are sterile, and males are absent from the surveyed population. These results suggest that M. smithii might be obligately asexual. To place the origin and maintenance of asexual reproduction in M. smithii in an evolutionary context, I use molecular phylogenetic and population-genetic methods to (i) test if M. smithii reproduces asexually throughout its distribution range; (ii) infer if asexuality evolved once or multiple times; (iii) date the origin of asexual reproduction in M. smithii; and (iv) elucidate the cytogenetic mechanism of thelytokous parthenogenesis. During field collecting for these studies throughout the Neotropics, I discovered a new species of obligate social parasite in the genus Mycocepurus. Social parasites are of great interest to evolutionary biology in order to elucidate mechanisms demonstrating how parasites gained reproductive isolation from their host species in sympatry. I describe this new parasite species, characterize its morphological and behavioral adaptations to the parasitic lifestyle, and discuss the parasite’s life history evolution in the context of social parasitism in fungus-growing ants. The dissertation research integrates population-genetic, phylogenetic, physiological and morphological approaches to advance our understanding of the evolution of reproductive systems and diversity of life-history traits in animals.Item Evolutionary ecology and natural history of fungus-growing ants : host-switching, divergence, and asexuality(2007-05) Himler, Anna Grace, 1972-; Mueller, Ulrich G.Host-switch associated divergence is an important generator of diversity among insects. Here, I investigate whether host-switching plays a role in fungus-growing ant divergence. There are over 210 known species of ants that cultivate fungus as their primary food source. This diversity of ants and their fungal cultivars offers a rich comparative system to investigate the complexities of host-switch associated divergence. This work complements previous studies utilizing the fungus-growing ant system to investigate coevolution, speciation, conflict and cooperation. In chapter one, I introduce the system and discuss features that make it ideal for studying evolutionary and ecological aspects of host-switch associated divergence. In chapter two, I examine whether switching to a new cultivar crop could trigger speciation events in two Central and South American species complexes of fungus-growing ants. Using behavior experiments and molecular phylogenetics, I investigate whether cultivar switches are associated with ant genetic divergence. It appears that, while some fungusgrowing ants specialize on a narrow group of fungal cultivars and do not switch, other fungus-growing ant species exchange fungal cultivars more frequently. Varying degrees of host-fidelity will have different consequences for coevolutionary dynamics in this symbiosis. In the course of investigating fungus-growing ant host-associated divergence, I discovered new facets of the system that are the subjects of chapters three and four. In chapter three, I investigate whether Mycocepurus smithii is the first completely asexual ant. Female mating anatomy studies, field and laboratory surveys, and DNA fingerprinting not only support complete asexuality in this widespread ant species, but also rule out bacteria and the fungal cultivars as causative agents inducing asexuality. In chapter four, I reconstruct the phylogenetic placement of a new species of fungusgrowing ant in the Cyphomyrmex longiscapus species group and discuss their unique nesting biology. In chapter five I detail the first population study of nest architecture and sex ratios in Mycetosoritis hartmanni, one of the few North American fungus-growing ants. As these studies attest, after over one hundred years of research on the fungusgrowing ant symbiosis, novel aspects of the system continue to emerge, providing a rich resource to test coevolutionary hypotheses within the context of this complex and ancient mutualism.Item Evolutionary ecology and natural history of fungus-growing ants: host-switching, divergence, and asexuality(2007) Himler, Anna Grace; Mueller, Ulrich G.Item The origins, maintenance, and conservation of biodiversity in spatial networks(2009-08) Economo, Evan Philip; Keitt, Timothy H.Biodiversity is distributed unevenly across geographic space and the tree of life. A key task of biology is to understand the ecological and evolutionary processes that generate these patterns. I investigate how the structure and geometry of a landscape, for example the sizes and arrangements of islands in an archipelago, affects processes contributing to the generation and conservation of biodiversity patterns. In the first chapter, I integrate two disparate bodies of theory, ecological neutral theory and network theory into a powerful new framework for investigating patterns of biodiversity in a complex landscape. I examine the consequences of network structure, such as size, topology, and connectivity, for diversity patterning across the metacommunity. The second chapter focuses on how the position of a node within a network controls local community (node) diversity. Network statistics, such as node centrality, are found to predict diversity patterns with more central nodes accumulating the most diversity. In the third chapter, I use the theory to evaluate how well fundamental concepts in conservation biology perform when neutral metacommunity processes generate diversity patterns. I find that contemporary diversity patterns are poor predictors of the long-term capacity of a network to support diversity, challenging a host of conservation concepts and applications. In the fourth chapter, I consider biodiversity dynamics in a network with a different model of speciation, where spatial structure is needed for divergence. In this case, speciation hotspots form where the dispersal properties of an organism and the spatial structure of the landscape coincide. In the final chapter I study the biodiversity of a natural structured metacommunity, the ants of the Fijian archipelago. I used a variety of collecting techniques to inventory the ant species occurring across a system of islands in the southwest Pacific. Approximately 50 new species were discovered, and the distributions of the ant species across the islands are firmly established. Radiations are observed in the genera Pheidole, Camponotus, Lordomyrma, Leptogenys, Cerapachys, Strumigenys, Poecilomyrma, and Hypoponera.Item The role of host switching in the evolution of the fungus-gardening ant symbiosis(2009-05) Mikheyev, Alexander Sergeyevich; Mueller, Ulrich G.The fungus-growing ants have long provided a spectacular example of co-evolutionary integration between distantly related taxa. Their ecological success has been thought to depend largely on the evolutionary alignment of reproductive interests between ants and fungi, following vertical transmission and the ancient suppression of fungal sexuality. In my dissertation I explored the role of lateral cultivar switching on the evolution of the fungus-gardening ant mutualism. First, I provided the first evidence for sexual reproduction in the attine cultivars, together with evidence of extensive independent long-distance horizontal transmission of fungal genes. In fact, fungi have greater gene flow relative to their host ants, crossing the Gulf of Mexico between Latin America and Cuba, over which the ants cannot readily disperse. Second, for the special case of leaf-cutting ants, I show that the cultivar population was largely unstructured with respect to host ant species, and leaf-cutting ants interact largely with a single species of fungus. Finally, I examined the effect of post-glacial expansion on the population structure of the northern fungus-gardening ant Trachymyrmex septentrionalis and compared it with that of its two microbial mutualists: a community of lepiotaceous fungal cultivars and associated antibiotic-producing Pseudonocardia bacteria. This comparison allowed me to examine the effect of historical biogeographic forces, such as climate-driven range shifts, on the population structure of the ants and their microbial symbionts. While neither the cultivar nor the Pseudonocardia genetic structure was correlated with that of the ants, they were significantly, though weakly, correlated with each other. These results suggest that biogeographic forces may act differently on macro- and microscopic organisms, even in the extreme case where some microbial mutualists may be vertically transmitted from generation to generation and share the same joint ecological niche. Thus, binding forces that appear to enforce host fidelity are relatively weak and pairwise associations between cultivar lineages and ant species have little opportunity for evolutionary persistence. Taken together, my studies suggest that mechanisms other than long-term pairwise interactions between ants and fungi (so-called partner fidelity feedback) govern the evolution of the mutualism over evolutionary time.