The response of floral traits associated with pollinator attraction to environmental changes expected under anthropogenic climate change in high-altitude habitats

Premise of research. While climate change will affect all plant species, those in high-altitude habitats cannot move to a more suitable habitat and must therefore adjust to their new environment. To determine how floral traits associated with pollinator attraction may respond to environmental changes, we examine whether these traits are phenotypically plastic, whether genetic variation exists for these traits to enable adaptation, and whether phenotypic plasticity itself has a genetic basis. Methodology. In high-altitude habitats, climate models predict increases in temperature and in spring and early summer rainfall. We grew Aquilegia coerulea plants from three natural populations in two greenhouse rooms, each set at a different temperature, with two water regimes per room. There were 2 water regimes x 3 populations x 17 families x 3 or 4 plants in each room. We measured floral display size, flower size, flower color, and reward traits. We used linear mixed models to examine the effects of family, population, and water and their interactions on the different traits within each room. Pivotal results. All floral traits showed genetic variation either within or among populations. Many floral traits exhibited phenotypic plasticity in response to water, and genetic variation in phenotypic plasticity was identified for two traits. The number of flowers increased while spur length and reflectivity decreased between the cool-dry and the warm-wet treatments. Conclusions. All floral traits examined had the potential to adjust to the changes in water expected under anthropogenic climate change in high-altitude habitats. As the plant adjusts to the new environmental conditions, the potential roles of phenotypic plasticity versus selection on a trait mean vary among floral traits. We discuss the implications of these expected changes in floral traits on pollinators and plant fitness.