First Advisor

Mitch Cruzan

Date of Award


Document Type


Degree Name

Bachelor of Science (B.S.) in Biology and University Honors




Insect pollinators -- Behavior, Plant spacing, Lasthenia -- Population regeneration -- Oregon -- Central Point -- Case studies, Pollination by insects




Premise: The response of animal pollinators to the spatial distribution of plants is crucial to understanding how plant-pollinator interactions contribute to plant reproductive processes. For plant species that aggregate in patches, population attributes- such as the size and distribution of patches and the density of plants- may affect pollinator visitation to a greater degree than characteristics of individual flowers. We examine how patch characteristics of the self-incompatible, vernal pool species Lasthenia californica (California goldfields) impact pollinator visitation using pollen load size and pollen germination rates to infer visitation patterns.

Methods: Plant density and the size and distribution of patches were estimated from aerial images captured during drone surveys of an upland prairie ecosystem in Southern Oregon. Pollen load sizes and number of compatible grains were quantified after staining with Alexander's Stain.

Key Results: We found that denser patches receive the highest deposition of compatible pollen on stigmas. Large patches have an accumulation of low quality pollen and reduced pollen germination success, most likely due to pollinators moving genetically-related pollen within patches.

Conclusions: Patterns of pollinator behavior inferred from the quantity and quality of pollen deposited on stigmas are consistent with optimal foraging theory. Pollinators optimize foraging by preferentially moving within patches that are larger or are in close proximity to larger patches. Our results suggest that individual patch characteristics do not significantly affect overall pollinator visitation rates, but the distribution of patches contributes to pollinator behavior.


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