Table A4 Literature values for pollen volume in 33 flowering species. Pollen volume was provided in literature sources directly or was calculated from literature values of pollen grain counts and pollen grain volumes. “Floral unit” is the scale at which pollen was collected from species, with capitulum measurements for members of Asteraceae and individual flower measurements for all other species. “Source species” were used when pollen production values were only available for morphologically similar species within the same genus and is left blank when the species itself was used.