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).