Insect pollinators of black cherry (Prunus serotina) in the northeastern United States
Open Access
- Author:
- Mc Laughlin, Rachel
- Graduate Program:
- Entomology
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- June 15, 2021
- Committee Members:
- Kelli Hoover, Thesis Advisor/Co-Advisor
Laura P Leites, Committee Member
Gary Felton, Program Head/Chair
Christina M Grozinger, Thesis Advisor/Co-Advisor - Keywords:
- pollinators
black cherry
Prunus serotina - Abstract:
- Many crops and wild plants benefit from visitation by pollinators. However, when compared to agricultural systems we know very little about pollinators in forests, especially their floral resource use. Studies that do examine plant-insect interactions in forest ecosystems focus on primarily understory herbaceous plants, despite the importance of canopy trees as a floral resource to pollinators. While most forest trees are wind pollinated, some rely on insects for successful seed set, such as black cherry (Prunus serotina). Since 2000, poor and erratic seed crops have been reported for black cherry, especially in areas such as the High Allegheny Plateau. Poor seed production has been implicated in difficulty with black cherry regeneration in forest stands. Given that black cherry is insect pollinated and unable to produce viable seed from self-pollination, a reduction in its seed crop could be due to a pollination deficit. However, its key pollinators are unknown. Identifying these pollinators and the factors that influence their abundance and fidelity is critical for supporting and enhancing black cherry seed production. I systematically assessed the pollinators of black cherry and examined how their presence and abundance, along with a several other abiotic and biotic factors, influenced viable seed production. To determine the most likely pollinators, I used a series of visual observations, hand collections, and pollen analyses of floral visitors to smaller black cherry trees in Centre County for which flowers were accessible to observation. I determined that andrenid bees are likely the most important pollinators. They were frequent visitors to black cherry flowers and consistently carried more black cherry pollen grains on average compared with other visitors. Additionally, the proportion of viable seed produced increased as the number of andrenids increased. Bees from the families Halictidae and Megachilidae also visited black cherry flowers and carried some pollen, suggesting they may contribute to pollination services. To determine the relationships between biotic and abiotic factors and viable seed production, I studied black cherry trees in the Allegheny National Forest, which is a forest habitat where decline in black cherry regeneration is especially apparent. I sampled potential pollinator communities in black cherry trees on the edge and interior of the forest using bowl traps, as well as documenting the surrounding forest composition and focal tree characteristics. I found that the proportion of viable seed produced again increased with the number of andrenids collected, and andrenids were most abundant on the forest edge. The proportion of viable seed produced was also greatest on edge trees, however it decreased as tree diameter at breast height and age increased. Overall, these studies suggest that andrenids were the most important pollinators of black cherry in forested, semi-natural, and developed landscapes in my study sites, and andrenid abundance and pollination services may be greater in edge habitats. However, the services offered by pollinators may be offset by other factors, like advanced tree age.