Pollen use and network comparison
Weighted estimates of pollen use show that pollinator species as a whole carried markedly different proportions of each Clarkia pollen. We were able to distinguish two different Lasioglossum taxa in our study, and found that the two identifiable taxa of Lasioglossumexhibited different rates of carrying each species of Clarkia . A putative Clarkia specialist, Lasioglossum pullilabre , carried all four species but was most associated with C. cylindrica , whereas L. (Dialictus) sp., a likely generalist, carried C. xantiana at higher rates (Figure 5). Furthermore, theClarkia specialist Hesperapis regularis carried the three most pollinator-sharing Clarkia species, C. cylindrica, C. unguiculata , and C. xantiana at almost equivalent rates, whileDiadasia angusticeps used C. speciosa almost to the exclusion of all other Clarkia (Figure 5).
Pollinator Clarkia visitation and Clarkia pollen use networks were similar (Figure 6). Overall network specialization, H2’, was 0.38 in the Clarkia visitation network, and 0.29 in theClarkia pollen-use network. Differences between networks were most apparent with the less-abundant pollinators: Apis mellifera(Apidae), Bombus sp. (Apidae), and Megachile sp.(Megachilidae). Each of these species were only captured on a subset ofClarkia , but carried multiple species of Clarkia . The honeybee, Apis mellifera , was only caught on C. xantianabut carried both C. cylindrica and C. xantiana ;Bombus sp. was only caught on C. unguiculata but carried both C. unguiculata and C. xantiana ; and Megachile sp. was caught on C. cylindrica and C. speciosa , but in fact carried all four Clarkia species (Figures 5 and 6).