Pollen richness and diversity
At the morphotype level, neither pollen richness, nor diversity varied
between the two bee species, among periods, or sites (Table 3). At the
family level, we observed a statistically significant interaction
between the effects of period and bee species on pollen richness, and a
statistically significant impact of both period and bee species on
pollen diversity (Table 3). There is greater statistical power at the
family relative to morphotype levels, due to the fewer number of
families and greater sample size associated with each family. Bumble
bees collected pollen from more plant families relative to honey bees in
period one, while the opposite pattern was observed in period three
(Fig. 3a). There were no statistically significant differences between
bee species in periods two, four, or five (Fig. 3a). Overall, bumble
bees collected pollen from (mean ± se) 4.26 ± 0.27 plant families, and
5.38 ± 0.35 plant morphotypes on a given day, while honey bees foraged
for pollen on 3.39 ± 0.27 plant families, and 4.36 ± 0.33 plant
morphotypes. Bumble bees collected more diverse pollen (mean ± se) (0.54
± 0.03) relative to honey bees (0.33 ± 0.04) (Table 3). In addition,
over both bee species, pollen diversity values were lower in period one
compared to periods three, four, and five (Fig. 3b).