Nutritional Ecology of Pseudacteon species (Diptera: Phoridae) and Its Impact on Their Fitness
Type of DegreeMaster's Thesis
Entomology and Plant Pathology
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Natural enemies, such as Pseudacteon parasitic flies, have the potential to provide sustainable suppression of imported fire ants, Solenopsis species. Multiple releases of various species of these flies have been made across the Southeastern United States for biological control of imported fire ants. Five species (P. cultellatus, P. curvatus, P. litoralis, P. obtusus, and P. tricuspis) have been released in Alabama, and P. curvatus is one of the established species in the state. Much research is being conducted on these flies, but very little is known about some aspects of their nutritional ecology and life-history strategies, which are essential for conservation biological control. The goal of the study was to address some important questions related to the nutritional ecology and life-history strategies of Pseudacteon phorid flies. In chapter II, a series of biochemical tests (i.e. anthrone tests) were used to test if P. curvatus utilizes sugar and lipid sources in the field, by comparing the nutrient levels in flies from three treatments: i) field-collected, ii) sugar-fed laboratory-reared (positive control), and iii) sugar-starved laboratory-reared (negative control) flies. Field-collected flies showed similar levels of gut sugars, body sugars and glycogen as sugar-fed laboratory-reared flies. When compared with sugar-starved laboratory-reared flies, field-collected flies showed marginal (but insignificant) increase in levels of gut sugars, body sugars and glycogen. Field-collected flies showed significantly higher lipid levels than both sugar-starved and sugar-fed laboratory-reared flies. The ecological significance and practical implications of these results are discussed. In chapter III, the effects of sugar feeding on the longevity of three phorid fly species, P. cultellatus, P. curvatus, and P. obtusus, were investigated. The timing of egg maturation and ovigeny of P. obtusus was also determined. The results showed significant and positive effect of sugar feeding on the longevity of all three species when compared with sugar-starved individuals. Comparing species, the largest-sized species, P. obtusus, lived the longest, with almost twice the lifespan of the smallest species, P. cultellatus. The ovaries of all specimens of newly emerged P. obtusus analyzed by light microscopy showed only post-vitellogenic oocytes, suggestive of a pro-ovigenic life history strategy. The ecological significance and practical implications of these results are discussed.