Pollen richness, diversity, and composition
Pollen richness and diversity were calculated separately for each bee species in a day at a given period and site. Pollen richness represents the number of plant families or morphotypes present in the daily collection of pollen by individual colonies. Pollen diversity included richness, but also accounted for the relative abundance of each pollen type. To estimate diversity, we calculated Simpson Diversity Index (1-D) which is constrained between 0 and 1, where 1 indicates greatest diversity. Diversity was calculated using the ‘diversity’ function in the ‘vegan’ package (Oksanen et al., 2019) in R (R. Core Team, 2013). We used the linear mixed model (proc mixed in SAS v. 9.4) described in the flower constancy section to determine the impact of bee species, time period, site, and their two-way interactions on pollen richness and pollen diversity.