Aerodynamics of Ephedra trifurca. III. Selective Pollen Capture by Pollination Droplets

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Abstract
Field data are presented on the physical properties (size and density) and the frequencies of pollen and spores found in 312 pollination droplets from Ephedra trifurca. These data are compared to predictions made with a computer model that simulated the behavior of pollen in an airflow environment created around E. trifurca ovules. The model accurately predicted the size and the percentage trends of pollen captured by E. trifurca pollination droplets. Atmospheric pollen sampling indicated that 0.5% of all airborne pollen was from Ephedra. However, 18.2% of all the pollen found in E. trifurca pollination droplets is from Ephedra. This value represented a 36-fold increase over airborne pollen density of E. trifurca. These data supported the hypothesis that ovules of E. trifurca operated as aerodynamic filtration devices. We suggest that the selective pollen capture by E. trifurca is an adaptation to anemophily.