Semester

Summer

Date of Graduation

2025

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Division of Plant and Soil Sciences

Committee Chair

Yong-Lak Park

Committee Member

Teiya Kijimoto

Committee Member

Rita Rio

Abstract

Effective pollination relies not only on the presence of pollinators but also on their morphological adaptations and reproductive biology. In this study, I investigated both the external hair morphology and the intracellular bacterial infection status of Osmia cornifrons, a solitary bee species increasingly used in orchard pollination due to its efficiency and early seasonal activity. Using Scanning Electron Microscopy (SEM), I characterized the distribution and structure of two major hair types present on the bee's body: branched and unbranched. Branched hairs were found widely distributed across the head, thorax, dorsal abdomen, and legs, and appeared to function primarily in incidental pollen collection. In contrast, unbranched hairs were found concentrated on the metasomal sterna and the inner surfaces of the legs and appear specialized for storing pollen for nest provisioning. Pollen viability assays confirmed that pollen grains collected from both hair types remained viable, as evidenced by pollen tube formation, but unbranched hairs were able to collect and deposit significantly more.

In addition to morphological analysis, I assessed the presence of the endosymbiotic bacterium Wolbachia, which is common in arthropods and known to manipulate host reproduction to create more females and thus more quickly fix the infection in the population. I screened 12 individuals from an O. cornifrons population located at the West Virginia University Organic Farm in Morgantown, WV. DNA was extracted from the abdominal tissue of 9 females and 3 males and subjected to PCR using Wolbachia-specific primers. Positive amplification was observed in 75% of tested individuals (6/9 females and 3/3 males). The relatively high infection rate and presence in both sexes suggest that Wolbachia may be established or nearing fixation in this population. Given its ability to induce parthenogenesis in haplodiploid species, the presence of Wolbachia may help explain recent observations of shifting sex ratios in this population, which historically has been male-biased.

Taken together, our findings may help contribute to a deeper understanding of the functional morphology and reproductive dynamics of O. cornifrons. These insights have important implications for the management and optimization of this species in agricultural systems, particularly in orchards requiring high-efficiency pollination and stable bee populations. Further research is warranted to explore the evolutionary origin of Wolbachia in North American populations and to assess its long-term effects on population structure, reproductive success, and pollination efficacy.

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