Abstract
Geographic differences in floral traits may reflect geographic
differences in effective pollinator assemblages. Independent local
adaptation to pollinator assemblages in multiple regions would be
expected to cause parallel floral trait evolution, although sufficient
evidence for this is still lacking. In this study, we investigated the
relationship between flower spur length and pollinator size in 16
populations of Aquilegia
buergeriana var. buergeriana distributed in four mountain
regions in the Japanese Alps. We also examined the genetic relationship
between yellow- and red-flowered individuals, to see if color
differences caused genetic differentiation by pollinator isolation.
Genetic relationships among 16 populations were analyzed based on
genome-wide single-nucleotide polymorphisms. Even among populations
within the same mountain region, pollinator size varied widely, and the
average spur length of A. buergeriana var. buergeriana in
each population was strongly related to the average visitor size of that
population. Genetic relatedness between populations was not related to
the similarity of spur length between populations; rather, it was
related to the geographic proximity of populations in each mountain
region. Our results indicate that spur length in each population evolved
independently of the population genetic structure but in parallel in
different mountain regions. Further, yellow- and red-flowered
individuals of A. buergeriana var. buergeriana were not
genetically differentiated. Unlike other Aquilegia species in
Europe and America visited by hummingbirds and hawkmoths, this species
is consistently visited by bumblebees in Japan. As a result, genetic
isolation by flower color has not occurred.