HABITAT-RELATED DIFFERENCES IN NECROPH- ILOUS SPECIES COMPOSITION: IMPLICATIONS FOR RESOURCE COMPETITION

Competition for resources is one of the most important selective factors influencing the expression of life history traits in both plants and animals (Darwin 1859). In grasslands, competition for resources such as nutrients, water, and space often is constrained by stochastic processes (Axelrod 1985). Disturbance factors such as fire, grazing by large herbivores, and fluctuating climatic conditions tend to alter the structure and magnitude of competition for limited resources among grassland communities more frequently than in other ecosystems (Snaydon 1987, van der Maarel 1993). Vertebrate carrion is one important resource used by both plants and animals in grasslands, providing a rich but ephemeral point source of nutrients (Towne 2000, Barton et al. 2013). A complex ecological network of vertebrate and invertebrate necrophilous animal species compete intensely for these carrion resources, often aided by specialized sensory and motility adaptations that aid resource discovery and sequestration (Putman 1978, Scott et al. 1979, DeVault et al. 2003)

Soil Preferences of Nicrophorus Beetles and the Effects of Compaction on Burying Behavior

The American burying beetle, Nicrophorus americanus Olivier was declared federally endangered in 1989 and many efforts to prevent this species from going extinct are ongoing. The Nicrophorus beetles bury small carcasses for reproductive purposes. They also reside in the soil during times of daily and seasonal inactivity. To better understand why N. americanus is in decline, the importance of soil texture, moisture, vegetation, gravel, the burial depth, and the effect of compaction on their burying behavior was examined. All tested species preferred moist soils with N. orbicollis having a significant preference for wet (pN. marginatus had a significant preference for wet, sandy loam soil with vegetation (pN. carolinus had a significant preference for wet, sandy soil with vegetation (pN. americanuspreferred moist sandy loam soil with vegetation and buried to depths of 20 cm. All species preferred loose over compact soil (p2. My results showed that soil compaction caused by normal off-road vehicles is well below the 3.0 kg/cm2 threshold and it is therefore unlikely to harm buried Nicrophorus beetles, including the endangered N. americanus. Advisor: David A. Wedi

Carrion Beetles (Coleoptera: Silphidae) of the Konza Prairie Biological Station

Pitfall traps were used to determine diversity, seasonality, and numbers of burying beetles on the Konza Prairie Biological Station (KPBS) during the summers of 1997 and 1998. Traps were baited with either beef liver (1997) or whole mouse carcasses (1997 and 1998); significantly more carrion beetles were found in traps baited with carcasses. A total of 1003 carrion beetles, representing 8 species, were trapped over the course of 1556 trap nights. One of these species, Necrophila americana Linneaus, had not previously been recorded in Riley County. One additional species was found at sites where pitfall trap bait was discarded, bringing the total number of KPBS silphid species to 9. Bait age was an important determinant in attracting silphids to pitfall traps, as numbers of beetles in the trap continued to increase with bait age up to 6 days. Grassland topography (upland vs. lowland trap sites) significantly affected the numbers of carrion beetles trapped. Grassland bum history did not affect number of carrion beetles trapped, but did seem to influence species diversit

Effects of Humidity and Temperature on Burying Beetle (Coleoptera: Silphidae) Survival and Flight

Terrestrial arthropods must prevent lethal desiccation during activity in dry environments. The small size of arthropods and high surface area to volume ratios increase the tremendous challenges to limit desiccation especially at warmer temperatures and lower humiditys. Among the insects, beetles in the family Silphidae include most species with shortened elytra and exposed abdomens. The silphids occur in communities that contain between 5 and 20 closely-related species that use carrion for food and reproduction. In the subfamily Nicrophorinae, burying beetles must locate appropriately sized, recently deceased vertebrates and bury them in the ground before they are discovered and consumed by predators or competitors. This activity requires the capacity for long sustained flights. The largest and most studied Silphidae is the endangered American burying beetle (ABB), Nicrophorus americanus, which is nocturnal and uses the largest carcasses. This study compared field data of activity patterns of the ABB with closely related species in Nebraska and Oklahoma. Laboratory studies of flight were conducted on Nicrophorus orbicollis, a proxy for ABBs, at temperatures between 10oC and 40oC, at three different relative humidity settings (INSERT THESE). The lowest and highest temperatures affected short flight activity while humidity did not. Desiccation rates were tested for three Silphinae and five Necrophorinae with different ecological and morphological traits at 23oC. Water loss rates varied among species and were not tightly linked to subfamily, size, or activity pattern, suggesting that other ecological factors are important for members of the Silphidae. These data are useful for modeling Silphidae niches and niche overlap based on environmental factors. Based on the results, increasing daily temperatures could affect the activity of day-active species, but are unlikely to limit the activity of ABB and other night—active species. Shifts in weather pattern and droughts are likely to affect carrion beetle communities, increasing some species while eliminating others.Entomology & Plant Pathology (MS

Distribution of Carrion-associated Beetles and Their Phoretic Mites Along an Urban-rural Gradient in Northeast Alabama

Global insect decline has been linked to urbanization, most notably by habitat fragmentation. These insects perform important ecological functions such as pollination, managing pests, and decomposing carrion to recycle nutrients back into the environment. Despite the importance of nutrient recycling behavior displayed by carrion-associated beetles, little research has been done on them in the southeastern US. Previous studies have found a relationship between urbanization, less favorable environmental conditions, carrion availability, and decreased insect diversity. However, no studies have been conducted in the southeastern United States on the relationship of these beetles to their environment despite having the highest rates of urbanization. The purpose of my research was to investigate the landscape variables and habitat variables that influence the carrion-associated beetle assemblages and their obligate phoretic mites found on those beetles in the southeastern US. Results from the landscape variable analyses showed considerable range in percent urban cover, patch size, and habitat heterogeneity across the 11 sites. Microhabitat variables were similar across all sites. Results of beetle and mite collections yielded a total of 263 beetles in 20 species and 40 mites of one species with similar evenness values across all sites. PCA and multiple regression analysis did not show significant relationships to environmental conditions. While these findings suggest that carrion associated ground beetles and their mites are not affected by fragmented habitats, caveats to this study include a limited number of sites, low beetle detection, and low intensity of developed landscape as in a major metropolitan area

Spatio-temporal niche patterns and thermal environmental cues: Implications for the persisitence of Nicrophorine burying beetles

The persistence of burying beetles (Silphidae: Nicrophorus) depends on the successful acquisition of a highly competitive resource. Breeding pairs of the Nicrophorine genus work together to bury and prepare a suitable carcass as food for their developing larvae. To understand the mechanisms allowing for the persistence of multiple burying beetle species in Nicrophorine-rich communities, this thesis explores how sympatric burying beetles utilize space and time to partition the carrion resource. Further, to explore how thermal environments influence the reproductive biology of burying beetles, the response of Nicrophorus marginatus, both within and across generations is measured by monitoring rearing behaviors, movement activity, and brood characteristics with exposure to varying temperature regimes. The results of these studies present an important interplay between space use and temporal activity patterns that may serve to mediate negative interactions among sympatric buying beetle species. Generally, where species exhibit high temporal or spatial overlap, they are segregated along the alternative niche dimension. Future work on this community of burying beetles should examine the trophic ecology of species that appear to overlap spatially and temporally. The findings of these studies also indicate that increasing temperatures may impose direct fitness consequences on populations of N. marginatus. While this species appears to exhibit higher activity in elevated temperatures, they also exhibited extended burial timing and significantly reduced reproductive success rates. Efforts should be made to increase our understanding of the thermal capacity of the Nicrophorine genus as a whole

Test of the Habitat Association and Seasonal Activity of the American Burying Beetle (Nicrophorus americanus) at Camp Gruber, OK, and the Benefits of Nicrophorus to Soil Fertility

Within the past decade, the American burying beetle, Nicrophorus americanus (ABB) have disappeared from approximately 90% of its former range. Efforts have been made to protect existing populations in the wild; however, ABB is considered a habitat generalist, which makes prioritizing conservation areas difficult. I sampled three habitat types: savannah, grassland, and forested areas. To compare across seasons, ABB were sampled from July 16, 2016 to November 12, 2017. I trapped a total of 1,756 unique individual ABB along with 10,448 individuals of 9 other Silphidae species. During the surveying period I found no significant difference in the habitat association of ABB. Overall trapping, forests had 6.0 ± 0.8, grasslands had 8.1 ± 1.2, and savannah had 8.2 ± 1.3 ABB per trap night. This suggests that across their active season, ABB are associated with all habitats at Camp Gruber. My data support the conclusion that ABB is a habitat generalist and is moving among the patches of different habitat types at Camp Gruber.In order to determine influence of Eastern redcedar and brood success on soil fertility, I conducted a laboratory experiment with Nicrophorus marginatus and various soil mixtures. Test containers consisted of: soil/rat/beetles (14) and soil/cedar/rat/beetles (14). Control containers consisted of the following combinations: soil only (3), soil/cedar (3), soil/rat (4) and soil/cedar/rat (4). Burial success and adult survival were recorded. Live weight and dried weight were taken for each larva produce from successful brood balls and the soil mixtures were analyzed. Cedar needles did not have a significant difference to the soil nutrients in each treatment type. Experimental containers with larva had significantly higher average soluble salt content when compared to all other treatments (df = 3; p < 0.001). There was significantly higher nitrate level in the containers with beetles and rats, especially those with larval broods (df = 3; p < 0.05). Experimental containers with successful broods had significantly higher levels of phosphorus compared to soil-only treatments (df = 3; p < 0.05) and potassium was significantly higher in treatments containing beetles (df = 3; p < 0.05). It appears that Nicrophorus species may improve soil fertility while rearing broods.Environmental Scienc

Carrion Beetles in Orchards and Ranches in Oklahoma and Investigation of Genes Associated with Antimicrobial Production

Family Silphidae, the carrion beetles, is a highly evolved family of Coleoptera that has members with unique social behaviors and physical abilities that allow them to utilize decaying vertebrate matter for sustenance and larval rearing. Two investigations were conducted to elaborate on the habitat association and gene expression of certain members of in the subfamily Nicrophorinae (burying beetles). The first investigation tested the effect of two forms of agricultural production on populations of Silphidae in eastern Oklahoma, with particular focus on the endangered American Burying Beetle (Nicrophorus americanus Olivier/ABB). Between 2017 and 2018, 10 weeks of field sampling was conducted in pecan orchards and cattle pastures of eastern Oklahoma, capturing a total of 2,338 Silphidae. Ultimately, no statistically significant differences were found between median capture values of Silphidae in either land usage (pecan orchard: [8]; cattle pasture [4]) in a majority of examined species, including the ABB. This finding suggests an overall trend toward generalism of habitat use by Silphidae in Oklahoma.The second investigation tested the nature of antimicrobial secretions used by Subfamily Nicrophorinae (burying beetles) in the preservation of carrion and the expression of genes in response to food availability. Using two species of burying beetle, Nicrophorus orbicollis Say, which has a typical life cycle, and Nicrophorus pustulatus Herschel, a brood parasite, gene expression of excised salivary glands was analyzed through RNA sequencing of beetles exposed to and denied ground beef as food. N. orbicollis had higher expression of innate immunity compounds when fed (6.58% of characterized sequences) than did N. pustulatus (5.19%) and a higher percentage of expression overall (7.14%/4.22%). These findings suggest the active bactericidal compounds in burying beetle secretions to be antimicrobial proteins produced by individual beetles in response to feeding.Together, these findings suggest that ABB can use areas of Oklahoma that are converted for pecan and ranching operations and that burying beetles have the potential to provide novel compounds for antibiotics or preservation of meat at room temperature.Entomology and Plant Patholog