Thesis

Interactions Between the Velvety Tree Ant Liometopum occidentale (Hymenoptera: Formicidae) and Pseudacteon Phorid Flies (Diptera: Phoridae)

Phorid fly parasitoids of ants are capable of decapitating their host during development and have been used as attempted biological control agents for imported fire ants. Little is known about the interactions between the native Velvety Tree Ant host, Liometopum occidentale, and its phorid fly parasitoids. This system is native to Southern California, occupying endangered habitats that have been in decline due to human development, changing weather patterns, and fierce competition from invasive species. To further understand the ecological significance and behavior of this system, I examined interactions of these parasitoids and the Velvety Tree Ants by observing and quantifying the behavioral displays exhibited in the presence of phorid fly parasitoids. To understand parameters of activity of the parasitoids, I measured temperature and time of day through five temporal periods encompassing the parasitoids' season. Two different phorid species were found attacking Liometopum occidentale: Pseudacteon californiensis Disney and an undescribed species of Pseudacteon herein designated Pseudacteon sp A. Because P. sp A keys to the genus Microselia Schmitz, I carried out molecular analyses to determine the phorids' evolutionary relationships. Based on analysis of three gene regions, Pseudacteon sp A and Pseudacteon californiensis are sister-species relative to other Pseudacteon parasitizing Solenopsis fire ants. The status of some North American phorid species, currently assigned to Microselia, needs to be further investigated.

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