Thesis (M.S.)--Florida State University, 2004. / Advisor: Dr. Walter R. Tschinkel, Florida State University, College of Arts and Sciences, Dept. of Biological Science. Title and description from dissertation home page (viewed Sept. 24, 2004). Includes bibliographical references.

Sexual conflict occurs when the fitness interests of males and females do not align with one another. The resolution of sexual conflict often depends on the level of control each sex has on the behavior in conflict. In Pogonomyrmex harvester ants with a genetically determined caste system, two separate lineages interbreed with one another during summer mating swarms. Diploid offspring sired by a single lineage develop into reproductive queens, while offspring sired by opposite-lineage parents develop into sterile workers. This results in sexual conflict, as males which mate with opposite lineage queens will produce only workers, resulting in no fitness benefit, while queens must mate with opposite-lineage males in order to obtain workers and survive. Despite these fitness differences, males do not discriminate between lineages prior to mating. One possible reason for the lack of male discrimination is that queens "mask" their identity cues, making discrimination difficult for males. In eusocial insects, identity cues are encoded by cuticular hydrocarbons (CHC’s) found on the exoskeleton of the insects. These cues contain information on the insect's reproductive status, sex, species, state, and nest membership. In addition to their communication functions, CHC’s also serve as desiccation-resistance molecules, preventing water from freely passing out of the cuticle. However, molecules that are best-suited for communication functions are poor desiccation resistance molecules, and molecules that are best-suited for waterproofing lack the diversity needed for communication; therefore, a tradeoff between these two functions is expected. In this dissertation, I explore sexual conflict in these ants and the chemical recognition cues that likely play a role in this conflict. To test for cryptic strategies in harvester ant mating swarms, I experimentally paired males and females from two interbreeding lineages of harvester ant with different fitness outcomes based on pairing, and measured the propensity to initiate copulation, pre-copulatory time, time in copula, and rate and amount of sperm transferred in each mating. Although females controlled copulation duration, males altered sperm transfer rates, resulting in no quantitative difference in total sperm transfer between lineages. To test for thermal constraints on the diversity and composition of cuticular hydrocarbon profiles, and changes in CHC profiles that occur in workers isolated from the queen, I surveyed the cuticular hydrocarbon profiles of a species complex of harvester ants. The CHC profiles of ants from more xeric environments showed evidence of constraints, while isolated workers differentiated from their queen-raised sisters, although not in queen-specific molecules. To test for queen identity masking and lack of discrimination ability in mating swarms, I tested for convergence in the CHC profiles of reproductives in two hybridizing lineages in response to the sexual conflict playing out in this species. Differences in CHC profiles were lost during the mating swarm, likely limiting male ability to discriminate between mates, limiting discrimination ability in mating swarms. To study the genetic regions that control CHC production, I created a physical linkage map of two of the interbreeding populations, and used that map to perform quantitative trait loci analysis on the cuticular hydrocarbon profile of recombinant males. One significant region associated with 13-methylnonacosane contained numerous odorant receptor genes, suggesting a link between that CHC production and the receptors that detect it, while a second region associated with n-pentacosane contained numerous genes that control expression levels. Overall, the genetic caste determination system in these ants leads to antagonistic coevolution between species. This coevolution is likely reinforced by the thermal constraints and exchange of recognition cues between species, lowering the ability of useful discrimination between lineages during mating swarms.

La variabilitat de la depredació de llavors en l'espai i temps poden oferir oportunitats a les males herbes per escapar dels depredadors. Els nivells de depredació en cereals de secà van ser dels més alts mai registrats cultius extensius (46-100%). El moment de producció de les llavors de males herbes es superposava amb el període de major demanda. La distribució espacial dels nius era no aleatòria. Els nius grans estaven més regularment distribuïts, els nius petits més agrupats. Les formigues van respondre amb taxes de depredació extremadament elevades (99-100%) a totes les densitats de llavors aplicades L. (1000-20.000 llavors m-2), amb una resposta denso-independent. La mida de rodal va influir en les taxes de depredació per formigues. Va ser major en els rodals més grans (99-100%) i menor en els més petits (78-94%). Aquesta investigació va quantificar la variabilitat espaciotemporal en la depredació de llavors de cereals de secà i l'eficàcia.Summary / La variabilidad de la depredación de semillas en el tiempo y espacio ofrecen oportunidades a las malas hierbas para escapar de los depredadores. Los niveles de depredación en cereales de secano fueron entre los más altos registrados jamás en cultivos extensivos (46-100%). El momento de producción de semillas de las malas hierbas se superponía con el período de mayor demanda. La distribución espacial de los nidos era no aleatoria. Los nidos grandes estaban más regularmente distribuidos, los nidos pequeños más agrupados. Las hormigas respondieron con tasas de depredación extremadamente elevadas (99-100%) a todas las densidades de semillas aplicadas (1.000 a 20.000 semillas m-2), con respuesta denso-independiente. El tamaño de parche influyó en las tasas de depredación por hormigas. Fue mayor en los parches más grandes (99-100%) y menor en los más pequeños (78-94%). Esta investigación cuantificó la variabilidad espacio-temporal de la depredación de semillas en cereales de secano y la eficacia. / The variability of seed predation in time and space may provide opportunities to weeds to escape predation. Seed predation rates by harvester ants in dryland cereals were among the highest ever recorded on arable fields (46-100%). The timing of weed seed shed overlapped with the period of highest demand. The spatial nest arrangement appeared to be non-random. The large nests were more or less regularly distributed, small nests tended to be more clumped. Harvester ants responded with extremely high predation rates (99-100 %) to all densities of Lolium multiflorum L. seeds applied (1000-20000 seeds m-2), and the response was density independent. Patch size influenced predation rates by harvester ants. Estimated seed predation rate was highest in the largest patches (99-100%), and lowest in the smallest patches (78-94 %). The current research quantified temporal and spatial variability in seed predation in dryland cereals and the influence to the efficacy of granivory.