The Effects of Prescribed Fire on Ant-Mediated Seed Dispersal in Missouri

Many aspects of animal-mediated seed dispersal are vulnerable to disturbance, including partner identity and dispersal quantity and quality. This dissertation explores ant-mediated seed dispersal of the herb Sanguinaria canadensis in Missouri Ozark oak forests, where prescribed fire is a common land management tool. In Chapter 1, I test the definition of a keystone seed disperser using absolute and relative contributions of different ant species to the quantity and distance of seed dispersal, based on field observations of S. canadensis seed dispersal. I demonstrate that the ant Aphaenogaster rudis is better described as a numerically dominant rather than keystone seed disperser, while other species in the genera Formica and Camponotus provide higher quality dispersal in the form of longer dispersal distances. In Chapter 2, I explore the effects of prescribed burning and physical litter removal on the number of seeds dispersed, dispersal distances, and disperser identity, using field observations of S. canadensis seed dispersal in burned, litter removal, and control plots. The overall seed-dispersing ant community and different species therein responded differently to burning and litter removal between two field seasons. Burning increased dispersal distance in 2020, but reduced dispersal distance in 2021. Finally, in Chapter 3, I consider the effects of burning and litter removal on ground-foraging and litter-dwelling ant communities, using three rounds of pitfall traps in 2020 (April, July, and September), and one round of pitfall and Berlese litter extraction in 2021. In 2020, overall ant abundance was higher in burn compared to control plots in September, but diversity peaked in July and was negatively affected by burning when weighting species by their relative abundances. Although both burning and litter removal reduced leaf litter cover in 2021, litter removal increased ground-foraging ant abundance but decreased litter-dwelling ant abundance on an area basis, and only affected ant diversity when considering ant abundance in 2020 pitfall traps and 2021 Berlese samples. The results of this dissertation suggest Missouri Ozark ant communities and their seed dispersal services are either positively affected by or relatively resilient to prescribed burning

PCR-DGGE method to assess the diversity of BTEX mono-oxygenase genes at contaminated sites

tmoA and related genes encode the a-subunit of the hydroxylase component of the major group (subgroup 1 of subfamily 2) of bacterial multicomponent monooxygenase enzyme complexes involved in aerobic benzene, toluene, ethylbenzene and xylene (BTEX) degradation. A PCR-denaturing gradient gel electrophoresis (DGGE) method was developed to assess the diversity of tmoA-like gene sequences in environmental samples using a newly designed moderately degenerate primer set suitable for that purpose. In 35 BTEX-degrading bacterial strains isolated from a hydrocarbon polluted aquifer, tmoA-like genes were only detected in two o-xylene degraders and were identical to the touA gene of Pseudomonas stutzeri OX1. The diversity of tmoA-like genes was examined in DNA extracts from contaminated and non-contaminated subsurface samples at a site containing a BTEX-contaminated groundwater plume. Differences in DGGE patterns were observed between strongly contaminated, less contaminated and non-contaminated samples and between different depths, suggesting that the diversity of tmoA-like genes was determined by environmental conditions including the contamination level. Phylogenetic analysis of the protein sequences deduced from the amplified amplicons showed that the diversity of TmoAanalogues in the environment is larger than suggested from described TmoAanalogues from cultured isolates, which was translated in the DGGE patterns. Although different positions on the DGGE gel can correspond to closely related TmoA-proteins, relationships could be noticed between the position of tmoA-like amplicons in the DGGE profile and the phylogenetic position of the deduced protein sequenc