Pollination-precision hypothesis data (Stewart et al. 2022)

Pollination-precision hypothesis: support from native honey bees and nectar bats
Alyssa B. Stewart, Carolina Diller, Michele R. Dudash, and Charles B. Fenster
New Phytologist 2022

Abstract
• The evolution of floral traits is often considered to reflect selection for increased pollination efficiency. Known as the pollination-precision hypothesis, increased pollination efficiency is achieved by enhancing pollen deposition on precise areas of the pollinator. Most research to date addressing this hypothesis has examined plant species that are a priori predicted to place pollen precisely, but we still lack comparisons with species predicted to have low pollination efficiency.
• We studied 39 plant species with diverse floral morphologies and measured the precision of pollen placement on two pollinator groups: honey bees (genus Apis) and nectar bats (family Pteropodidae). Pollen was collected from four locations of each pollinator’s body (bees: dorsal thorax, ventral thorax, dorsal abdomen, ventral abdomen; bats: crown, face, chest, wing) to calculate pollen placement precision using Pielou’s evenness index. We also quantified variation in floral design by scoring floral symmetry, corolla fusion, floral orientation, and stamen number.
• We confirm the importance of four floral character states (bilateral symmetry, fused corollas, horizontal orientation, and reduced stamen number) in promoting precise pollen placement on diverse pollinators.
• Our findings provide empirical support that the evolution of the four floral characters reflect selection for enhanced precision of pollen placed on pollinators.