Data from: Adaptive differentiation in floral traits in the presence of high gene flow in scarlet gilia (Ipomopsis aggregata)

Plant-pollinator interactions are thought to be major drivers of floral
trait diversity. However, the relative importance of divergent
pollinator-mediated selection versus neutral processes in floral character
evolution has rarely been explored. We tested for adaptive floral trait
evolution by comparing differentiation at neutral genetic loci to
differentiation at quantitative floral traits in a putative Ipomopsis
aggregata hybrid zone. Typical I. aggregata subsp. candida displays
slender white tubular flowers that are typical of flowers pollinated by
hawkmoths and subsp. collina displays robust red tubular flowers typical
of flowers pollinated by hummingbirds; yet hybrid flower morphs are
abundant across the East Slope of the Colorado Rockies. We estimated
genetic differentiation (FST) for nuclear and chloroplast microsatellite
loci and used a half-sib design to calculate quantitative trait divergence
(QST) from collection sites across the morphological hybrid zone. We found
little evidence for population structure and estimated mean FST to be
0.032. QST values for several floral traits including corolla tube length
and width, color, and nectar volume were large and significantly greater
than mean FST. We performed multivariate comparisons of neutral loci to
genetic correlations within and between populations and found a strong
signal for divergent selection, suggesting that specific combinations of
floral display and reward traits may be the targets of selection. Our
results show little support for historical subspecies categories, yet
floral traits are more diverged than expected due to drift alone.
Non-neutral divergence for multivariate quantitative traits suggests that
selection by pollinators is maintaining a correlation between display and
reward traits.