Pollen-mediated gene dispersal by hawkmoths and bumble bees visiting Aquilegia coerulea in two distinct landscapes

The pollen dispersal patterns of bumble bees and hawkmoths visiting flowers of the Rocky Mountain columbine are contrasted. Plants at Grand Canyon National Park (GCNP) are found in isolated patches while plants at Cedar Breaks National Monument (CBNM) are more evenly distributed. We set up six patches at GCNP and marked 90 plants. We replicated the spatial arrangement at CBNM where we marked 104 plants. The marked plants at each site simultaneously displayed a receptive flower. During the six-day receptivity period, day-visiting bumble bees or evening-visiting hawkmoths were excluded from visiting half of the flowers in each patch. Progeny arrays (18.5 ± 0.97 seeds/fruit) were genotyped at five microsatellite loci (2310 seeds total) from the 69 surviving plants at CBNM and 49 at GCNP. A hierarchical TwoGener analysis done separately for each pollinator indicated that most of the genetic variation in the pollen pool was found within mothers, with significant differences among mothers and some differences among patches, leaving only small differences among sites. Comparisons of pollinators within sites showed a similar pattern but indicated no pollinator effect on pollen pool variability. Results obtained using Kindist suggested a higher probability of moving pollen longer distances for hawkmoths relative to bumble bees. These results also showed differences between sites and some indication that bumble bees are more affected by changes in landscape attributes relative to hawkmoths.