DISCUSSION
In community ecology, the relationship between plants and pollinators is
critical to understanding how pollinators contribute to plant community
functioning. Though observations of pollinator visitation can be used to
infer how plants interact with each other through shared pollinators,
visitation does not necessarily correspond to pollen transfer (Mayfield
2001; Popic et al. 2013; Ballantyne et al. 2015, 2017; Barrios et al.
2016). Metabarcoding has been critical for understanding if and when
bees use certain pollen resources in plant communities (Galliot et al.
2017; Lucas et al. 2018), but to date has only reliably shown if bees
use pollen resources from specific species in flowering plant
communities, not to what extent (Bell et al. 2017, Bell et al. 2019).
This is because relative read abundance from PCR can be unreliable for
accurate use in amplicon quantitation in a sample.
Using our new approach, we have shown that shared pollinators amongClarkia species have preferences for different species ofClarkia , and are also inconstant foragers, often carrying more
than one species of pollen in their pollen balls at a time. Though the
trends of pollen use were similar to what we had expected from
pollinator visitation observations alone, our molecular analysis added
nuance to how pollinators used Clarkia resources. We have
additionally shown that our new method, qAMPseq, estimates the relative
amounts of pollen species in a sample.