Pollinator movements and pollen-mediated gene dispersal were quantifie
d in experimental populations of square-stemmed monkeyflower (Mimulus
ringens), a wetland perennial herb with a mixed-mating system. Each po
pulation consisted of genets with unique multilocus combinations of ho
mozygous genotypes, facilitating assignment of paternity to all sample
d seeds. Replicate arrays were planted at each of three spacings spann
ing the range of densities typically observed in natural M. ringens po
pulations. In all six arrays the distribution of gene dispersal distan
ces differed significantly from the distribution of pollinator flight
movements. The mean gene dispersal distance was 1.46 times as far as t
he mean pollinator flight distance. These differences were probably ca
used by pollen carryover as bumblebees visited up to 12 M. ringens pla
nts on a single foraging trip. Although gene movements exceeded pollin
ator flight distances, estimates of neighbourhood size were consistent
ly low, ranging from 1.66 to 5.53. Therefore, high levels of random lo
cal genetic differentiation are likely in this species.